\documentclass[10pt]{article}

\usepackage{fullpage}
\usepackage{setspace}
\usepackage{parskip}
\usepackage{titlesec}
\usepackage[section]{placeins}
\usepackage{xcolor}
\usepackage{breakcites}
\usepackage{lineno}
\usepackage{hyphenat}





\PassOptionsToPackage{hyphens}{url}
\usepackage[colorlinks = true,
            linkcolor = blue,
            urlcolor  = blue,
            citecolor = blue,
            anchorcolor = blue]{hyperref}
\usepackage{etoolbox}
\makeatletter
\patchcmd\@combinedblfloats{\box\@outputbox}{\unvbox\@outputbox}{}{%
  \errmessage{\noexpand\@combinedblfloats could not be patched}%
}%
\makeatother


\usepackage{natbib}




\renewenvironment{abstract}
  {{\bfseries\noindent{\abstractname}\par\nobreak}\footnotesize}
  {\bigskip}

\titlespacing{\section}{0pt}{*3}{*1}
\titlespacing{\subsection}{0pt}{*2}{*0.5}
\titlespacing{\subsubsection}{0pt}{*1.5}{0pt}


\usepackage{authblk}


\usepackage{graphicx}
\usepackage[space]{grffile}
\usepackage{latexsym}
\usepackage{textcomp}
\usepackage{longtable}
\usepackage{tabulary}
\usepackage{booktabs,array,multirow}
\usepackage{amsfonts,amsmath,amssymb}
\providecommand\citet{\cite}
\providecommand\citep{\cite}
\providecommand\citealt{\cite}
% You can conditionalize code for latexml or normal latex using this.
\newif\iflatexml\latexmlfalse
\providecommand{\tightlist}{\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}%

\AtBeginDocument{\DeclareGraphicsExtensions{.pdf,.PDF,.eps,.EPS,.png,.PNG,.tif,.TIF,.jpg,.JPG,.jpeg,.JPEG}}

\usepackage[utf8]{inputenc}
\usepackage[ngerman,english]{babel}



\usepackage{float}








\begin{document}

\title{Is Cesarean Section Protective against Anal Incontinence in Women after
Obstetric Anal Sphincter Injury (OASI)? A Systematic Review and
Meta-Analysis}



\author[1]{Emily Carter}%
\author[1]{Rebecca Hall}%
\author[1]{Kelechi Ajoku}%
\author[2]{Jenny Myers}%
\author[1]{Rohna Kearney}%
\affil[1]{Manchester University NHS Foundation Trust}%
\affil[2]{The University of Manchester Faculty of Biology Medicine and Health}%


\vspace{-1em}



  
  \date{May 27, 2024}


\begingroup
\let\center\flushleft
\let\endcenter\endflushleft
\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
Objective: Approximately 50\% women who give birth after Obstetric Anal
Sphincter Injury (OASI) develop anal incontinence (AI) over their
lifetime. We review current evidence for protective benefit of planned
cesarean section (CS) to prevent AI after OASI. Design and setting:
Systematic review and meta-analysis according to prospectively published
methodology. Population and methods: All studies reporting outcomes
after an OASI and subsequent birth by any mode. Main outcome measures:
AI measurement after OASI and subsequent birth. Total AI, new/worsening
AI, quality of life, satisfaction, regret. Results: 86 of 2472 screened
studies met inclusion criteria. All studies contributing to
meta-analyses were at high risk of bias. There was no evidence of
difference in new or worsening AI after subsequent vaginal birth (VB)
compared to subsequent CS after OASI across all time periods (p=0.53: CI
0.72-1.19; 9 studies, 2104 participants); [?]2y (p=0.83: CI 0.65-1.72; 7
studies, 569 participants) or [?]5y after subsequent birth (p=0.39: CI
0.65-1.18; 2 studies; 1535 participants). There was no difference
between subsequent CS or VB in asymptomatic women or for other AI or QOL
outcomes. There was no evidence of difference in AI in women who
subsequently delivered vs those who did not (p=0.9: CI 0.71-1.34; 10
studies, 970 participants); or pre- subsequent birth vs post-subsequent
birth (p=0.31; CI 0.51-1.25, 13 studies, 5496 participants).
Conclusions: Due to evidence quality (majority non-randomised studies)
we are unable to determine whether planned cesarean is protective
against AI after OASI. Higher quality data is required to guide practice
in this area, specifically in asymptomatic women and for long-term
outcomes.%
\end{abstract}%



\sloppy


\section*{Title page}

{\label{title-page}}

\textbf{Is Cesarean Section Protective against Anal Incontinence in
Women after Obstetric Anal Sphincter Injury (OASI)? A Systematic Review
and Meta-Analysis}

\subsection*{Authors}

{\label{authors}}

Emily Carter\textsuperscript{1}

Rebecca Hall\textsuperscript{1}

Kelechi Ajoku\textsuperscript{1}

Jenny Myers \textsuperscript{2,3}

Rohna Kearney\textsuperscript{1,2}

\subsection*{Affiliations}

{\label{affiliations}}

1. The Warrell Unit, Saint Mary's Hospital,

Manchester University NHS Foundation Trust, Manchester Academic Health
Science Centre, Manchester, UK

2. Division of Developmental Biology and Medicine, School of Medical
Sciences, University of Manchester, Manchester, UK

3. Maternal and Fetal Health Research Centre, University of Manchester,
Manchester, UK

Corresponding author:

Emily Carter,

Clinical Research Fellow in Urogynaecology, ST7 Registrar in Obstetrics
and Gynaecology,

emily.carter@manchester.ac.uk

07901228188

The Warrell Unit, Saint Mary's Hospital,

Manchester University NHS Trust, Manchester Academic Health Science
Centre,

Oxford Road, Manchester, UK. M13 9WL.

Shortened running title:

Mode of Birth after OASI and Anal Incontinence, A Systematic Review.

\par\null

\section*{Abstract}

{\label{abstract}}

Objective:

Approximately 50\% women who give birth after Obstetric Anal Sphincter
Injury (OASI) develop anal incontinence (AI) over their lifetime. We
review current evidence for protective benefit of planned cesarean
section (CS) to prevent AI after OASI.

Design and setting:

Systematic review and meta-analysis according to prospectively published
methodology.

Population and methods:

All studies reporting outcomes after an OASI and subsequent birth by any
mode.

Main outcome measures:

AI measurement after OASI and subsequent birth. Total AI, new/worsening
AI, quality of life, satisfaction, regret.

Results:

86 of 2472 screened studies met inclusion criteria. All studies
contributing to meta-analyses were at high risk of bias.

There was no evidence of difference in new or worsening AI after
subsequent vaginal birth (VB) compared to subsequent CS after OASI
across all time periods (p=0.53: CI 0.72-1.19; 9 studies, 2104
participants); [?]2y (p=0.83: CI 0.65-1.72; 7 studies, 569 participants)
or [?]5y after subsequent birth (p=0.39: CI 0.65-1.18; 2 studies; 1535
participants). There was no difference between subsequent CS or VB in
asymptomatic women or for other AI or QOL outcomes. There was no
evidence of difference in AI in women who subsequently delivered vs
those who did not (p=0.9: CI 0.71-1.34; 10 studies, 970 participants);
or pre- subsequent birth vs post-subsequent birth (p=0.31; CI 0.51-1.25,
13 studies, 5496 participants).

Conclusions:

Due to evidence quality (majority non-randomised studies) we are unable
to determine whether planned cesarean is protective against AI after
OASI. Higher quality data is required to guide practice in this area,
specifically in asymptomatic women and for long-term outcomes.

Funding:

This study was not externally funded.

Keywords:

Obstetric Anal Sphincter Injury, OASI, OASIS, Anal Incontinence, Mode of
Birth, Shared Decision Making, Cesarean, Vaginal Birth, Planned Birth,
Quality of Life, Recurrent OASI



\textbf{Introduction}

Obstetric Anal Sphincter Injury (OASI) is the commonest cause of anal
incontinence (AI) affecting young women. The incidence of OASI in
primiparous women tripled to 5.9\% in the UK between 2000-2012 (1)
equating to 3,500 women in the UK annually. AI is defined as the
involuntary loss of solid or liquid stool and or flatus. Women with OASI
are between two to three times more likely to develop AI than women
having an uncomplicated vaginal birth (2). Specific risk factors for AI
include parity, degree of OASI and age (as risk of AI increases over a
woman's lifetime) (3). Women who have recurrent OASI and fourth degree
tears are particularly affected by more frequent and severe long-term
symptoms of AI (4, 5). At least 10\% of women who are initially
asymptomatic after OASI become symptomatic by three years (6).

The presence of AI is the most important determiner of women's quality
of life (QOL) after OASI (7). The 'OASIS syndrome' has been described in
a study of women with AI after OASI. Feelings include being unclean,
isolation, grief, anxiety, a feeling of mutilation, loss of dignity,
guilt and a negative effect on motherhood, sexual intimacy and partner
relations (8). Women with OASI have worse longer-term quality of life
outcomes than women without OASI; this significantly correlates with
symptoms of AI and number of OASI births (9). All symptoms of AI can be
profoundly upsetting to women; Jango et al demonstrated a Wexner score
[?]2 sufficient to affect quality of life in the long-term after OASI
(10).

In women who deliver again after OASI, incidence of AI is particularly
high; 48\% by 2-5 years in one study (11). The long-term incidence of AI
was 58.8\% after a fourth-degree tear and 41.0\% after a third-degree
tear at a median of 8.5 years after a second birth in a population-based
study (12). Additional risk factors in these women include pre-existing
symptoms of AI, either `transient AI' (13) or `permanent AI' (2) after
index birth. AI is therefore of vital consideration for all women
choosing their mode of birth in subsequent pregnancies after OASI. Based
on expert opinion, the Royal College of Obstetricians and Gynaecologists
(RCOG) recommends medical discussion regarding birth options for
symptomatic women or those with abnormal endoanal ultrasonography and/or
manometry. The American College of Obstetricians and Gynaecologists
(ACOG) recommend offering a cesarean section (CS) to women experiencing
either AI or perineal breakdown after birth.

Birth choice is personal and can be emotive. There is a wide variation
in practice between units including access to specialist perineal
clinics and use and interpretation of anorectal investigations including
endoanal ultrasound (EAUS) and anorectal manometry (ARMS). A 2014 survey
of UK women demonstrated that only one third had access to a perineal
clinic, and less than one fifth had access to endoanal ultrasound after
OASI (14). Protocols outlining interpretation of anorectal
investigations to directivity counsel women on planned mode of birth
(MOB) after OASI differ between units (11, 15, 16, 17, 18, 19). Evidence
suggests that the majority of women in the UK are counselled regarding
subsequent MOB based on their symptoms and preferences alone (14).

This study aims to systematically review and meta-analyse current
evidence to determine whether CS is protective against the development
of AI after OASI.



\section*{Method}

{\label{method}}

Systematic review and meta-analysis were performed according to our
prospectively published protocol (PROSPERO CRD42022372442) using PRISMA
guidelines (20). Authors were contacted to provide data in a suitable
format for meta-analysis if not supplied. Core outcome sets for OASI
have not been published, but there are published protocols in
development seeking to establish this for OASI (21), perineal trauma
(22) and the effects of episiotomy and OASI (23). Patients and the
public were not directly involved in conducting this review.

\subsection*{Eligibility criteria}

{\label{eligibility-criteria}}

\subsubsection*{Participants/Population:}

{\label{participantspopulation}}

All women \textgreater{}18y who have had an OASI and a subsequent birth
by any mode. OASI is defined as a 3rd or 4th degree tear by the Sultan
classification (24). Inclusion and exclusion criteria are described
(S2).

\subsubsection*{Intervention:}

{\label{intervention}}

Planned elective CS in a subsequent birth after an OASI, analysed by
intention-to treat. Observational studies comparing vaginal birth to all
CS (emergency and elective) included with risk of bias assessment.

\subsubsection*{Comparison:}

{\label{comparison}}

Planned vaginal birth. Emergency CS was analysed with vaginal birth
outcomes via intention-to-treat when possible. When data were not
provided (i.e. when emergency CS was included with planned CS) the study
is included with risk of bias assessed.

\subsubsection*{Outcomes:}

{\label{outcomes}}

Our primary outcome is AI (solid, liquid, flatus) after subsequent birth
by any mode; including but not limited to; St Marks Score, Wexner score,
EPAQ, clinical description. AI outcome is stratified by time if
available: [?]2y and [?]5y.

Subgroup analysis for patients asymptomatic after index birth.

Our secondary outcomes are: QOL, regret with MOB choice, satisfaction
with MOB choice, fecal urgency, obstructive defecation, change in AI
pre- and post- subsequent birth, AI in women after subsequent birth vs
no subsequent birth, repeat OASI rate and adverse events (return to
theatre, organ injury).

\subsubsection*{Measures of effect}

{\label{measures-of-effect}}

Dichotomous outcomes are presented as risk ratio/odds ratios with 95\%
CI. Continuous outcomes presented as mean difference with 95\% CI.

\subsection*{Search strategy}

{\label{search-strategy}}

MeSH subject heading and database-specific truncated search terms were
used to avoid excluding potential studies. Three concepts were
implemented for the search strategy: (1) identification of all types of
anal sphincter or anal canal injury, (2) identification of all
subsequent birth by any mode and (3) identification of all types of anal
incontinence. The search terms and strategy are detailed (S1).

\subsection*{Information sources}

{\label{information-sources}}

Search strategy was executed in Ovid MEDLINE/PubMed 1946-2022 (Ovid),
Embase 1974-2022 (Ovid), CINAHL(EBSCOhost) 1937-2022, Cochrane Combined
1996-2022, Clinical trials and Google Scholar from inception to
1\textsuperscript{st} December 2022.

\subsection*{Study selection}

{\label{study-selection}}

\subsubsection*{Setting}

{\label{setting}}

We included randomised-controlled trials and non-randomised studies
including observational, cohort, cross-sectional, case-control and
retrospective reviews in any publication format which provided data for
our outcomes of interest for a birth after OASI (Table S1).

\subsubsection*{Data extraction (selection and
coding)}

{\label{data-extraction-selection-and-coding}}

All title and abstract screening (EC, RH), full text review (EC, RH),
data extraction (EC, KA, RH) and risk of bias assessments (EC, RH), were
completed by two blinded independent reviewers according to standard
Cochrane methodology. Screening took place using Rayyan review software
(25). Discrepancies were resolved by a third reviewer (RK). We describe
characteristics of included studies in Table S1.

\subsubsection*{Risk of bias assessment}

{\label{risk-of-bias-assessment}}

Risk of bias was undertaken using the ROBINS-I tool (26).

\subsubsection*{Strategy for data
synthesis}

{\label{strategy-for-data-synthesis}}

Dichotomous outcomes were meta-analysed in RevMan 5.4 and are presented
as risk ratio/odds ratios with 95\% confidence intervals. Continuous
outcomes are presented as mean difference with 95\% confidence
intervals. When significant statistical heterogeneity was demonstrated
on meta-analysis (including but not limited to I\selectlanguage{ngerman}²\textgreater{}40\%)
random effects modelling is used for meta-analyses. Studies providing
data on incidence of AI are included in the `total AI' meta-analysis,
whilst studies demonstrating a change in AI score or the development of
new AI symptoms in previously asymptomatic women after a subsequent
birth after OASI are included in the `new or worsening AI'
meta-analysis.

Subgroup analysis

{\label{subgroup-analysis}}

Women who were symptomatic of anal incontinence after the first birth vs
those who were asymptomatic.

\par\null

\section*{Results}

{\label{results}}

2472 studies were identified. 86 studies met inclusion criteria after
full text review (PRISMA diagram S3).

\subsection*{Characteristics of included
studies:}

{\label{characteristics-of-included-studies}}

Studies varied in quality and methodology. One RCT and non-randomised
studies including retrospective reviews, case-control, service
evaluations and questionnaire studies were included (Table S1).

For measurement of our primary outcome, eight studies used a validated
questionnaire (7, 12, 17, 18, 27, 28, 29, 30) and four studies did not
use a validated method of symptom assessment, relying on description
alone (18, 31, 32, 33). It was possible to analyse data for an
asymptomatic group of women after index OASI for two studies (Figure 3D)
(27, 28).

Risk of bias:

All ten studies contributing data to meta-analysis for the primary
outcome were at high risk of bias for at least one domain (Figure 1).
One multicentre RCT contributed data to the analysis; however only
14.7\% of 222 women randomised had a third-degree tear at the time of
the index birth and the other 85.3\% women were recruited after a
forceps birth and had an anal sphincter defect identified on endoanal
ultrasound, which was considered a surrogate marker for OASI. 71\% women
randomised in this study had an intact perineum at index birth (28). One
prospective cohort study to 6 months follow up was included (7). Other
studies were confounded by inclusion of women symptomatic of AI or were
biased by retrospective reporting of outcomes after treatment
allocation, failure to account for important factors such as parity or
to analyse by the intention-to-treat approach, (e.g. by excluding
emergency cesareans, or including elective and emergency cesarean data
together). Studies were also biased by retrospective recall of AI
symptoms from patients, different populations included (e.g. patients
with OASI diagnosed sonographically, exclusion of women with OASI
recurrence, sphincter injury not classified by Sultan criteria), use of
non-validated symptom assessment tools (e.g. patient description),
selective outcome reporting, use of multiple analyses, use of
counselling pathways advising CS for different groups, (e.g. patients
with symptoms, 4\textsuperscript{th} degree tear or EAUS defects), and
methodological limitations (e.g. retrospective service evaluation,
follow-up questionnaire with limited response rate).

\subsection*{Data heterogeneity:}

{\label{data-heterogeneity}}

A wide range of methods and protocols for counselling mode of subsequent
birth were described based on patient symptoms alone, endoanal
ultrasound, anorectal manometry, and findings on 3D transperineal
ultrasound. Seven studies used EAUS to counsel women regarding mode of
subsequent birth (18, 28, 29, 32, 33, 34, 35) and four used ARMS (18,
29, 32, 33) (S4). One study used 3D-TPUS but did not contribute data to
meta-analysis (11).

Recurrence of OASI

49 studies reported recurrence of OASI in women undergoing subsequent
vaginal birth (S5). These included 10 national or state database studies
(4, 12, 36, 37, 38, 39, 40, 41, 42, 43, 44), 3 US state databases (36,
38, 40) and 1 Canadian state database (44). Three studies were
multicentre studies (27, 28, 45) and 32 studies were single centre
studies (11, 17, 29, 30, 31, 32, 33, 34, 46, 47, 48, 49, 50, 51, 52, 53,
54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69). 29
studies took place in a university or teaching hospital setting, (11,
17, 27, 28, 30, 32, 33, 34, 45, 46, 47, 49, 51, 52, 53, 54, 55, 56, 57,
58, 59, 60, 61, 62, 63, 65, 67, 68, 69) and six were in a district
general hospital setting (29, 31, 48, 50, 64, 66).

The mean index OASI rate was 3.31\% and mean recurrence rate was 6.6\%
across all studies (7413 cases: range 1.9-25\%, S5). Index OASI rates
were higher in teaching hospitals (6.13\% n=32) compared to
population-based studies (4.34\% n=11) and district general hospitals
(3.2\% n=6). Recurrent OASI rates were higher in district general
hospitals (11.74\% range 6.6-25\% n=6) but similar in teaching hospitals
(6.02\% range 1.9\%-13.4\% n=32) and population-based studies (5.59\%
range 2.1-7.2\% n=11). A summary of rOASI rates provided by
population-based studies (Figure 2) and all studies (S5) is described.

Incidence of AI after subsequent vaginal birth (VB) and subsequent CS
after OASI

The incidence of AI after a subsequent birth after OASI was reported by
twenty-two studies. 12 studies (one RCT and 11 non-randomised studies)
were suitable for meta-analysis as they included data for both CS and VB
in a suitable form for pooling, and their characteristics are described
(S4, Table S1) (7, 12, 18, 27, 28, 29, 31, 32, 33, 34). Some
participants from one study (70) were included in a later publication
(29) therefore we excluded the earlier study from meta-analyses. Two
studies described satisfaction with MOB choice (17, 34), two studies
described regret with MOB choice (27, 30) and two studies described
quality of life after subsequent birth (7, 12). 11 studies were not
suitable for meta-analysis (11, 13, 17, 46, 65, 67, 69, 71, 72, 73, 74)
as they either did not contain a comparison group or did not contribute
data in an interpretable format (and either were not able to provide
this or did not respond on contact with the corresponding author).

There was no evidence of a difference in deterioration in AI (new or
worsening symptoms) after subsequent VB compared to CS after OASI across
all follow up time periods studied (Figure 3A: p=0.74; CI 0.72-1.19, 9
studies- 1 RCT 8 non-RCT, 2104 participants). There was no evidence of a
difference for short-term symptoms at 3-24 months (Figure 3B: p=0.71; CI
0.65-1.72, 7 studies, 569 participants) or long-term symptoms at \selectlanguage{english}[?]5
years (Figure 3C: p=0.39; CI 0.65-1.18, 2 studies, 1536 participants)
between groups. There was no evidence of a difference in AI between VB
and CS in studies who recruited only asymptomatic women (Figure 3D:
p=0.43; CI 0.71-2.20, 2 studies, 220 participants).

The total incidence of AI after subsequent birth after OASI may be
higher after CS than VB; the wide CI is consistent with little effect or
harm (Figure 4: p=0.03; 95\% CI 1.08-3.47; 6 studies, 2253
participants). These studies include women who were symptomatic
pre-subsequent birth. Symptomatic women were more likely to have
subsequent CS than VB across the studies. The presence of pre-existing
AI symptoms is therefore a significant confounder.

The incidence of incontinence of solid or liquid stool, flatal
incontinence and fecal urgency does not differ between women who have a
subsequent CS vs VB (S6). There is no evidence of a difference in levels
of satisfaction (17, 34) and regret (27, 30) (S7); regret is inversely
proportional to satisfaction (30). There was no evidence of a difference
in QOL overall (S7); one study demonstrated higher levels of
`incontinence impact' and `physical limitations' in women having CS vs
VB (7). Reduction in QOL is directly proportional to patient symptoms of
AI after OASI (70).

In a study not suitable for meta-analysis, patients subsequently
delivering by CS had a significantly lower Vaiezy score compared with
subsequent VB, and those following MOB recommendations also demonstrated
significantly less AI (65). Another study demonstrated higher Wexner
scores overall in women delivering by CS vs VB, however there was no
difference in average pre- and post- birth scores in the CS and VB
groups (17). These studies demonstrate the difficulties with
interpreting results from individual sites, the confounder of a higher
symptomatic population in the CS group and widespread practice
variation.

\subsubsection*{Other outcomes}

{\label{other-outcomes}}

No studies reported on symptoms of irritable bowel syndrome, obstructive
defecation, blood loss or length of stay.

Anal incontinence and subsequent birth by any mode

Twelve studies have investigated whether there is a difference in AI in
women who have a subsequent birth compared to women who have not had a
subsequent birth after OASI. Ten studies were suitable for meta-analysis
(S8A) (13, 31, 55, 73, 75, 76, 77, 78, 79, 80). There is no evidence of
a difference in AI in women who have a subsequent birth by any mode vs
those who have not (S8A: p=0.9; CI 0.71-1.34, 10 studies 970
participants). One study looked at QOL with a subsequent birth vs no
subsequent birth (S8B). There was no difference in QOL outcomes for
women with a subsequent birth by any mode compared to those who did not
(55). A previous review meta-analysed this outcome in 2016 (35). Only
one further study has been added since this time (7).

\subsection*{Anal incontinence pre- and post- subsequent
birth}

{\label{anal-incontinence-pre--and-post--subsequent-birth}}

The incidence of AI in the same patients pre- and post- subsequent birth
by any mode does not differ between a mixed symptomatic and asymptomatic
patient group across all time periods studied (S9: p=0.31; CI 0.51-1.25,
13 studies, 5496 participants) (7, 12, 13, 18, 31, 32, 33, 34, 70, 74,
76, 81, 82).

\par\null

\section*{Discussion}

{\label{discussion}}

\subsection*{Main findings}

{\label{main-findings}}

\subsubsection*{Preventative value of CS for AI after
OASI}

{\label{preventative-value-of-cs-for-ai-after-oasi}}

This analysis does not demonstrate a protective benefit for routine
elective CS in preventing new or worsening symptoms of AI after OASI in
a group of women who are both symptomatic and asymptomatic after their
index OASI. This was analysed from either a deterioration on a validated
scoring system or a description of new or worsening symptoms in women by
study authors after a subsequent birth after OASI. There is no evidence
of difference in deterioration of AI between women who deliver by CS
compared to women who deliver by VB after OASI overall, in the
shorter-term or longer-term (Figure 3A-C). For two studies in which an
asymptomatic group was analysed, there was also no evidence of a
difference in AI symptoms in the short-term; however there are
significant limitations to both studies (Figure 3D).

Regarding the certainty of the results, all included studies were at
high risk of bias for at least one outcome (Figure 1). This was due to:
limitations with the population recruited; non-randomisation to
treatment outcomes; inclusion of symptomatic women causing systemic
bias; retrospective analysis; failure to analyse by intention-to-treat
(emergency CS group included with elective CS group or excluded) and a
lack of validated outcome data measurement (Figure 2). We do not have
data to counsel specific groups; i.e. symptomatic women, asymptomatic
women, women with recurrent OASI.

\subsubsection*{Long term data}

{\label{long-term-data}}

In the longer term, there is evidence from a larger population-based
study that women subsequently delivering by VB after OASI may experience
worsening of AI symptoms 5-12y after subsequent birth compared to CS;
however, this was not significant on the author's multivariate analysis
(12). The study relied on retrospective recall of patient symptoms after
index birth. EAUS and ARMS were not used to routinely counsel women
regarding subsequent birth; it was national practice for symptomatic
women to undergo CS and asymptomatic women to undergo subsequent VB.

The other study providing long-term data outcomes compared two different
control groups of 50 patients however this study was not powered to
investigate long term AI symptoms between these groups (27). Therefore,
both studies in our meta-analysis have significant limitations and we
need higher quality data to investigate differences in long-term AI
symptoms in asymptomatic women after OASI who deliver by VB or CS.

\subsubsection*{Recurrence of OASI}

{\label{recurrence-of-oasi}}

Women who sustain an OASI recurrence have poorer long term incontinence
outcomes than women who deliver without an OASI (5); studies included in
this review did not provide data for this specific outcome. Rates of
index OASI are higher in teaching and university hospitals compared to
population-based studies and district-general hospitals (DGHs). However,
rates of recurrent OASI are highest in DGHs. There is an extremely wide
variation in OASI recurrence rates reported across studies, representing
a 25-fold difference. This may relate to training in OASI detection and
participation in research in some units, differences in OASI detection
rates and classification over time, regional differences in obstetric
practice and care to avoid recurrence e.g. by using OASI care bundles in
some units.

\subsection*{Strengths and limitations}

{\label{strengths-and-limitations}}

This comprehensive review summarises the current evidence for whether
elective cesarean section is protective against the development of AI
after OASI. It uses a robust prospectively published systematic
methodology to double-extract data and appraise the risk of bias of this
data by two independent study authors. This is an extremely important
area clinically as AI has a profound negative effect on the lives of
young women, OASI is common, and AI is very common after OASI. This area
is under-researched; current guidelines utilise level 4 evidence and
there is consequently widespread variation in clinical practice.

This study meta-analyses both (1) the total incidence of AI after
subsequent VB compared to subsequent CS after OASI and (2) the presence
of new or worsening AI after subsequent VB compared to subsequent CS
after OASI. To our knowledge, it is the first study to investigate both
outcomes. It highlights challenges appraising evidence from
non-randomised mode of birth studies due to significant confounding
caused by including women with pre-existing symptoms of AI. It is
therefore difficult to provide clinically interpretable information on
the preventative value of CS against worsening AI from existing
published data.

\subsubsection*{Asymptomatic vs symptomatic
women}

{\label{asymptomatic-vs-symptomatic-women}}

This review is limited by the methodology of the published data,
particularly the ability to extract values for just women who are
symptomatic or asymptomatic after index OASI. When counselling women
clinically, this is an important factor. Most studies are service
evaluations which include both symptomatic and asymptomatic women as one
group. Additionally, most published data do not used a validated
incontinence score to pair data pre- and post- birth after OASI
therefore it is difficult to extract data for women who have `new' or
`worse' AI after birth.

\subsubsection*{Quality of the data}

{\label{quality-of-the-data}}

The vast majority of included studies were at high risk of bias for at
least one outcome. This was due to: limitations with the population
recruited; non-randomisation to treatment outcomes; inclusion of
symptomatic women causing systemic bias; retrospective analysis; failure
to analyse by intention-to-treat (emergency cesarean group included with
elective cesarean group or excluded); and a lack of validated outcome
data assessment (Figure 1). All studies except two included women with
pre-existing AI symptoms.

\subsubsection*{Data heterogeneity}

{\label{data-heterogeneity-1}}

One difference between studies is the use of EAUS, ARMS and 3D-TPUS to
assess anal sphincter defects and counsel women alongside symptoms to
undergo planned VB or planned CS after OASI (Table S1, S4). Defects on
EAUS are significantly correlated with symptoms of AI both in women with
a history of OASI diagnosed at birth (55\% have a persistent sphincter
defect and 38\% have AI) and in those without (13\% have sphincter
defects and 14\% have AI) (83). We include all women in these
meta-analyses however it would be valuable to appreciate the role of
EAUS, ARMs and 3D-TPUS in the long term in guiding practice,
specifically whether CS is valuable in preventing AI in asymptomatic
women with defects/abnormal physiology who undergo subsequent birth.

\subsubsection*{Deviations from study
protocol}

{\label{deviations-from-study-protocol}}

Although our protocol aim was to stratify AI by follow up time period
(short-term (\selectlanguage{english}[?]1y), medium-term (\textgreater{}1y \textless{}5y),
long-term (\selectlanguage{english}[?]5y)) this was not due to the ranges in follow-up time period
employed by particular studies (S4) (12, 31, 33, 34). Instead, we
meta-analyses two time periods; 3-24 months (short term) and \selectlanguage{english}[?]5y (long
term).

\subsection*{Interpretation of results}

{\label{interpretation-of-results}}

This systematic review has not demonstrated a protective effect of CS
over VB to prevent new or worsening AI symptoms after OASI in the
short-term. Data presented in this meta-analysis represents a mixed
group of symptomatic and asymptomatic women and nearly all studies were
at high risk of bias and short follow up duration. It therefore does not
reliably assess an effect of subsequent MOB on long-term AI outcomes, or
provide individualised risk assessment for groups of women who are
symptomatic or asymptomatic after OASI.

Evidence to support counselling women after OASI is limited. There is a
paucity of data on long-term outcomes and knowledge about women's
preferences and decision-making (84). Factors predicting worse AI with
subsequent birth after OASI include transient or ongoing AI symptoms
after index birth (13), fourth-degree tear (5, 24) and recurrent OASI
(4). Factors predicting better AI outcomes with subsequent birth after
OASI include absence of AI after index birth (13), normal anorectal
physiology (29), lesser degree of injury (24) and absence of injury at
subsequent birth (4).

\subsection*{Practical and research
recommendations}

{\label{practical-and-research-recommendations}}

The evidence included in this review is limited and comes mostly from
service evaluations undertaken on mixed groups of women (17, 18, 19, 29,
31, 32, 70, 82). Higher-quality evidence is required to enable
clinicians to personalise the risk of future AI based on index birth
factors, maternal risk and current pregnancy details in women who
deliver after OASI. This should differentiate the risk for asymptomatic
and symptomatic women. Research to ascertain the value of anorectal
physiology investigations in predicting longer term AI outcomes would be
beneficial and enable standardisation of antenatal counselling pathways.

\section*{Conclusion}

{\label{conclusion}}

This systematic review and meta-analysis summarises the results of 84
studies investigating outcomes in women who subsequently deliver after
OASI. Evidence is of low quality and does not support the routine
practice of elective cesarean to prevent new or worsening AI symptoms in
a mixed symptomatic and asymptomatic group of women. There are
significant limitations to existing published data, specifically
relating to counselling of asymptomatic women and regarding long-term AI
outcomes. Further research is required so that women can be provided
with personalised risk indicators for AI for birth after OASI.

\section*{Disclosure of interests}

{\label{disclosure-of-interests}}

The authors have no relevant financial, personal, political,
intellectual or religious conflicts of interest to declare.

\section*{Contribution to Authorship}

{\label{contribution-to-authorship}}

EC: Project design and conception. Prospectively registered and
independently performed aspects of the systematic review and
meta-analysis including title/abstract screening, data extraction, data
analysis, risk of bias assessments, statistical analysis, interpretation
of results and project writeup.

RH: Performed independent title/abstract screening, independent double
data extraction for the recurrence of OASI data and independent risk of
bias assessments.

KA: Performed independent double data extraction for the included
studies.

JM: Contributed substantially to writeup and clinical interpretation of
results.

RK: Instrumental in project design and conception. Performed data
analysis and substantially contributed to project writeup and
interpretation of results.

\section*{Details of Ethical approval}

{\label{details-of-ethical-approval}}

Ethical approval was not required for this study. The primary review
author has completed review author training in systematic review with
Cochrane.

\section*{Funding}

{\label{funding-1}}

No additional funding was obtained to undergo this work.



\section*{References}

{\label{references}}

1. Gurol-Urganci I, Cromwell DA, Edozien LC, Mahmood TA, Adams EJ,
Richmond DH, et al. Third- and fourth-degree perineal tears among
primiparous women in England between 2000 and 2012: time trends and risk
factors. BJOG. 2013;120(12):1516-25.

2. LaCross A, Groff M, Smaldone A. Obstetric anal sphincter injury and
anal incontinence following vaginal birth: a systematic review and
meta-analysis. J Midwifery Womens Health. 2015;60(1):37-47.

3. Fornell EU, Matthiesen L, Sjodahl R, Berg G. Obstetric anal sphincter
injury ten years after: subjective and objective long term effects.
BJOG. 2005;112(3):312-6.

4. Jango H, Langhoff-Roos J, Rosthoj S, Sakse A. Recurrent obstetric
anal sphincter injury and the risk of long-term anal incontinence. Am J
Obstet Gynecol. 2017;216(6):610 e1- e8.

5. Jango H, Langhoff-Roos J, Rosthoj S, Saske A. Long-term anal
incontinence after obstetric anal sphincter injury-does grade of tear
matter? Am J Obstet Gynecol. 2018;218(2):232 e1- e10.

6. Reid AJ, Beggs AD, Sultan AH, Roos AM, Thakar R. Outcome of repair of
obstetric anal sphincter injuries after three years. Int J Gynaecol
Obstet. 2014;127(1):47-50.

7. Webb SS, Sitch A, MacArthur C. The impact of mode of subsequent birth
after obstetric anal sphincter injury on bowel function and related
quality of life: a cohort study. Int Urogynecol J. 2020;31(11):2237-45.

8. Keighley MR, Perston Y, Bradshaw E, Hayes J, Keighley DM, Webb S. The
social, psychological, emotional morbidity and adjustment techniques for
women with anal incontinence following Obstetric Anal Sphincter Injury:
use of a word picture to identify a hidden syndrome. BMC Pregnancy
Childbirth. 2016;16(1):275.

9. Nilsson IEK, Akervall S, Molin M, Milsom I, Gyhagen M. Severity and
impact of accidental bowel leakage two decades after no, one, or two
sphincter injuries. Am J Obstet Gynecol. 2023;228(4):447 e1- e19.

10. Jango H, Langhoff-Roos J, Rosthoj S, Sakse A. Wexner score and
quality of life in women with obstetric anal sphincter injury. Int
Urogynecol J. 2020;31(6):1115-21.

11. van der Vlist M, Oom D, van Rosmalen J, van Ovost A, Hogewoning C.
Parturition mode recommendation and symptoms of pelvic floor disorders
after obstetric anal sphincter injuries. Int Urogynecol J.
2020;31(11):2353-9.

12. Jango H, Langhoff-Roos J, Rosthoj S, Sakse A. Mode of delivery after
obstetric anal sphincter injury and the risk of long-term anal
incontinence. Am J Obstet Gynecol. 2016;214(6):733 e1- e13.

13. Bek KM, Laurberg S. Risks of anal incontinence from subsequent
vaginal delivery after a complete obstetric anal sphincter tear. Br J
Obstet Gynaecol. 1992;99(9):724-6.

14. Ismail SI. A national questionnaire survey of consultants and middle
grade doctors' perception of foundation doctors in obstetrics and
gynaecology in the United Kingdom. Arch Gynecol Obstet.
2014;290(6):1159-67.

15. Badri H, Fowler G, Lane S. The role of anal manometry in the
follow-up of women with obstetric anal sphincter injuries (OASI). Int
Urogynecol J. 2023;34(2):399-404.

16. Cassis C, Giarenis I, Mukhopadhyay S, Morris E. Mode of delivery
following an OASIS and caesarean section rates. Eur J Obstet Gynecol
Reprod Biol. 2018;230:28-31.

17. Fitzpatrick M, Cassidy M, Barassaud ML, Hehir MP, Hanly AM,
O'Connell PR, et al. Does anal sphincter injury preclude subsequent
vaginal delivery? Eur J Obstet Gynecol Reprod Biol. 2016;198:30-4.

18. Karmarkar R, Bhide A, Digesu A, Khullar V, Fernando R. Mode of
delivery after obstetric anal sphincter injury. Eur J Obstet Gynecol
Reprod Biol. 2015;194:7-10.

19. Okeahialam NA, Thakar R, Sultan AH. Effect of a subsequent pregnancy
on anal sphincter integrity and function after obstetric anal sphincter
injury (OASI). Int Urogynecol J. 2021;32(7):1719-26.

20. Carter E KR, Hall R. Is Caesarean Section for Subsequent Delivery
Protective Against Fecal Incontinence in Women with Obstetric Anal
Sphincter Injury (OASI)? A systematic review and meta-analysis protocol
{[}Systematic review registration{]}. 2022 {[}updated 2022.

21. Daly O, Mol B, Rogers R, Sultan A, Thakar R, Webb R, et al. The
CO-OPT Study: Core Outcomes in Obstetric Anal Sphincter Injury
Prevention and Treatment COMET website2017 {[}Available from:
https://www.comet-initiative.org/studies/details/959.

22. Doumouchtsis SK, Rada MP, Pergialiotis V, Falconi G, Haddad JM,
Betschart C. A protocol for developing, disseminating, and implementing
a core outcome set (COS) for childbirth pelvic floor trauma research.
BMC Pregnancy Childbirth. 2020;20(1):376.

23. Gachon B, Schmitz T, Artzner F, Parant O, De Tayrac R, Ducarme G, et
al. A core outcome set development for a French national prospective
study about the effect of mediolateral episiotomy on obstetric anal
sphincter injury during operative vaginal delivery (INSTRUMODA). BMC
Pregnancy Childbirth. 2021;21(1):251.

24. Okeahialam NA, Taithongchai A, Thakar R, Sultan AH. The incidence of
anal incontinence following obstetric anal sphincter injury graded using
the Sultan classification: a network meta-analysis. Am J Obstet Gynecol.
2023;228(6):675-88 e13.

25. Ouzzani M, Hammady H, Fedorowicz Z, Elmagarmid A. Rayyan-a web and
mobile app for systematic reviews. Syst Rev. 2016;5(1):210.

26. Sterne JA, Hernan MA, Reeves BC, Savovic J, Berkman ND, Viswanathan
M, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised
studies of interventions. BMJ. 2016;355:i4919.

27. Bogeskov RA, Nickelsen CN, Secher NJ. Anal incontinence in women
with recurrent obstetric anal sphincter rupture: a case control study. J
Matern Fetal Neonatal Med. 2015;28(3):288-92.

28. Abramowitz L, Mandelbrot L, Bourgeois Moine A, Tohic AL, Carne
Carnavalet C, Poujade O, et al. Caesarean section in the second delivery
to prevent anal incontinence after asymptomatic obstetric anal sphincter
injury: the EPIC multicentre randomised trial. BJOG. 2021;128(4):685-93.

29. Jordan PA, Naidu M, Thakar R, Sultan AH. Effect of subsequent
vaginal delivery on bowel symptoms and anorectal function in women who
sustained a previous obstetric anal sphincter injury. Int Urogynecol J.
2018;29(11):1579-88.

30. Edwards M, Kobernik EK, Suresh S, Swenson CW. Do women with prior
obstetrical anal sphincter injury regret having a subsequent vaginal
delivery? BMC Pregnancy Childbirth. 2019;19(1):225.

31. Dilmaghani-Tabriz D, Soliman N. Delivery after third- or fourth-
degree perineal tear. BJOG An International Journal of Obstetrics and
Gynaecology. 2012;119:42.

32. Harkin R, Fitzpatrick M, O'Connell PR, O'Herlihy C. Anal sphincter
disruption at vaginal delivery: is recurrence predictable? Eur J Obstet
Gynecol Reprod Biol. 2003;109(2):149-52.

33. Tetzschner T, Sorensen M, Lose G, Christiansen J. Anal and urinary
incontinence in women with obstetric anal sphincter rupture. Br J Obstet
Gynaecol. 1996;103(10):1034-40.

34. Young R, Bates L, The S, King J. Mode of delivery following
obstetric anal sphincter injury: a 7-year retrospective review and
follow-up cohort survey. Int Urogynecol J. 2022;33(12):3365-9.

35. Webb SS, Yates D, Manresa M, Parsons M, MacArthur C, Ismail KM.
Impact of subsequent birth and delivery mode for women with previous
OASIS: systematic review and meta-analysis. Int Urogynecol J.
2017;28(4):507-14.

36. Ampt AJ, Roberts CL, Morris JM, Ford JB. The impact of first birth
obstetric anal sphincter injury on the subsequent birth: a
population-based linkage study. BMC Pregnancy Childbirth. 2015;15:31.

37. Baghestan E, Irgens LM, Bordahl PE, Rasmussen S. Risk of recurrence
and subsequent delivery after obstetric anal sphincter injuries. BJOG.
2012;119(1):62-9.

38. Dandolu V, Gaughan JP, Chatwani AJ, Harmanli O, Mabine B, Hernandez
E. Risk of recurrence of anal sphincter lacerations. Obstet Gynecol.
2005;105(4):831-5.

39. Edozien LC, Gurol-Urganci I, Cromwell DA, Adams EJ, Richmond DH,
Mahmood TA, et al. Impact of third- and fourth-degree perineal tears at
first birth on subsequent pregnancy outcomes: a cohort study. BJOG.
2014;121(13):1695-703.

40. Parmar S, Towner D, Xing G, Wallach S. Recurrent anal sphincter
injury: a population based study. American Journal of Obstetrics and
Gynaecology. 2012;206(1):S150.

41. Pirhonen J, Haadem K, Gissler M. Delivery after an obstetric anal
sphincter tear. Arch Gynecol Obstet. 2020;301(6):1479-84.

42. Spydslaug A, Trogstad LI, Skrondal A, Eskild A. Recurrent risk of
anal sphincter laceration among women with vaginal deliveries. Obstet
Gynecol. 2005;105(2):307-13.

43. van Bavel J, Hukkelhoven C, de Vries C, Papatsonis DNM, de Vogel J,
Roovers JWR, et al. The effectiveness of mediolateral episiotomy in
preventing obstetric anal sphincter injuries during operative vaginal
delivery: a ten-year analysis of a national registry. Int Urogynecol J.
2018;29(3):407-13.

44. Boggs EW, Berger H, Urquia M, McDermott CD. Recurrence of obstetric
third-degree and fourth-degree anal sphincter injuries. Obstet Gynecol.
2014;124(6):1128-34.

45. D'Souza JC, Monga A, Tincello DG, Sultan AH, Thakar R, Hillard TC,
et al. Maternal outcomes in subsequent delivery after previous obstetric
anal sphincter injury (OASI): a multi-centre retrospective cohort study.
Int Urogynecol J. 2020;31(3):627-33.

46. Ali A, Glennon K, Kirkham C, Yousif S, Eogan M. Delivery outcomes
and events in subsequent pregnancies after previous anal sphincter
injury. Eur J Obstet Gynecol Reprod Biol. 2014;174:51-3.

47. An V, D'Souza B, Thomas E, Schierlitz L, Woods R, Keck J. Obstetric
Anal Sphincter Injuries; Outcome and Function after Subsequent
Deliveries. Colorectal Disease. 2014;16(0):89.

48. Antonakou A, Papoutsis D, Henderson K, Qadri Z, Tapp A. The
incidence of and risk factors for a repeat obstetric anal sphincter
injury (OASIS) in the vaginal birth subsequent to a first episode of
OASIS: a hospital-based cohort study. Arch Gynecol Obstet.
2017;295(5):1201-9.

49. Basham E, Stock L, Lewicky-Gaupp C, Mitchell C, Gossett DR.
Subsequent Pregnancy Outcomes After Obstetric Anal Sphincter Injuries.
Obstetrical and Gynaecological Survey. 2014;69(2):78-9.

50. Bayar E, Mukri F, Ramalingam K. A clinical audit; Risk of subsequent
perineal trauma after previous obstetric anal sphincter injury. Archives
of Disease in Childhood: Fetal and Neonatal Edition. 2013;98(0).

51. Dakin A, Eogan M. Birth preferences and delivery outcomes after
previous obstetric anal sphincter injury. Eur J Obstet Gynecol Reprod
Biol. 2021;266:125.

52. Daly J, Sultan AH, Van delft KW, Thakar R. Outcome of childbirth
after previous obstetric anal sphincter injury. International
Urogynecology Journal and Pelvic Floor Dysfunction 2013;24(0):S69-70.

53. Davies D, Bahl R. Recurrence rate of third degree perineal tears at
St Michael's Hospital. Archives of Disease in Childhood: Fetal and
Neonatal Edition. 2013;98(0).

54. Doumouchtsis SK, Anparasan A, Chis-Ster I, Abbas N, Gauthaman N.
Recurrent obstetric anal sphincter injuries (OASIS): Is prediction
possible? Neurourology and Urodynamics. 2014;33(6):883-4.

55. Fradet-Menard C, Deparis J, Gachon B, Sichitiu J, Pierre F, Fritel
X, et al. Obstetrical anal sphincter injuries and symptoms after
subsequent deliveries: A 60 patient study. Eur J Obstet Gynecol Reprod
Biol. 2018;226:40-6.

56. Izett ML, Giarenis I, Thiagamoorthy G, Robinson D, Cardozo L.
Obstetric anal sphincter injury (OASIS): What happens next?
International Urogynecology Journal and Pelvic Floor Dysfunction.
2015;26(1):S42-3.

57. Lowder JL, Burrows LJ, Krohn MA, Weber AM. Risk factors for primary
and subsequent anal sphincter lacerations: a comparison of cohorts by
parity and prior mode of delivery. Am J Obstet Gynecol. 2007;196(4):344
e1-5.

58. Moffatt J, Basude S. Factors influencing mode of delivery in women
with previous OASI. BJOG: An International Journal of Obstetrics and
Gynaecology. 2022;129(0):56.

59. Nausheen S, Roberts AJ, Wakefield N, Canavan L, Dinardo L. Mode of
delivery and perineal injury following primary obstetric anal sphincter
injury. BJOG: An International Journal of Obstetrics and Gynaecology.
2014;121(0):228.

60. Nutaitis A, Kollikonda S, Yao M, Hickman L, Propst K. OBSTETRIC ANAL
SPHINCTER INJURY: GUIDANCE FOR FUTURE DELIVERY ROUTE. Female Pelvic
Medicine and Reconstructive Surgery. 2022;28:S11-S2.

61. Park Y, Nguyen N, Vatsayan A. Does maternal age at subsequent
pregnancy, maternal weight and birth weight of baby impact on risk of
subsequent severe perineal tears following third and fourth degree
perineal tears in first pregnancy? BJOG: An International Journal of
Obstetrics and Gynaecology. 2015;122(0):392-3.

62. Ramalingam K, Roberts A. Pregnancy outcomes after recurrent
obstetric anal sphincter injuries. Female Pelvic Medicine and
Reconstructive Surgery. 2014;20(0):S157-S8.

63. Rahim A, Bhide A, Mackdermott N, Tailor V, Patel M, Digesu A, et al.
Mode of delivery following OASIS: A 5-year follow up study of subsequent
deliveries after 3rd and 4th degree vaginal tears. Neurourology and
Urodynamics. 2021;40:S42-S3.

64. Thiel M, Behrens R. Outcome of subsequent delivery in women with
previous obstetric anal sphincter injury (OASIS). International
Urogynecology Journal and Pelvic Floor Dysfunction. 2015;26(1):S129-30.

65. Vasseur A, Lepigeon K, Baud D, Horsch A, Meyer S, Vial Y, et al.
Counseling after perineal laceration: does it improve functional
outcome? Int Urogynecol J. 2019;30(6):925-31.

66. Viner A, Narrainen Poulle T. Incidence and recurrence of obstetric
anal sphincter injury (OASIS). BJOG: An International Journal of
Obstetrics and Gynaecology. 2017;124:11.

67. Wegnelius G, Hammarstrom M. Complete rupture of anal sphincter in
primiparas: long-term effects and subsequent delivery. Acta Obstet
Gynecol Scand. 2011;90(3):258-63.

68. Yogev Y, Hiersch L, Maresky L, Wasserberg N, Wiznitzer A, Melamed N.
Third and fourth degree perineal tears--the risk of recurrence in
subsequent pregnancy. J Matern Fetal Neonatal Med. 2014;27(2):177-81.

69. Yousif S, Eogan M. Mode of delivery after previus anal sphincter
injury (ASI): Role of the perineal clinic. Irish Journal of Medical
Science. 2011;180(0):S122.

70. Scheer I, Thakar R, Sultan AH. Mode of delivery after previous
obstetric anal sphincter injuries (OASIS)--a reappraisal? Int Urogynecol
J Pelvic Floor Dysfunct. 2009;20(9):1095-101.

71. An V, D'Souza B, Thomas E, Schierlitz L, Woods R, Keck J. Obstetric
anal sphincter injuries; outcome and function after subsequent
deliveries. Colorectal Disease. 2014;16:89.

72. De Leeuw JW, Vierhout ME, Struijk PC, Hop WC, Wallenburg HC. Anal
sphincter damage after vaginal delivery: functional outcome and risk
factors for fecal incontinence. Acta Obstet Gynecol Scand.
2001;80(9):830-4.

73. Faltin DL, Boulvain M, Stan C, Epiney M, Weil A, Irion O.
Intraobserver and interobserver agreement in the diagnosis of anal
sphincter tears by postpartum endosonography. Ultrasound Obstet Gynecol.
2003;21(4):375-7.

74. Younis J, Rajendran N, Walker H, Wolf G, McWilliams D, Bearn P.
Deterioration of anal sphincter function following second vaginal
delivery in women with previous intrapartum perineal tears. 2010;12:20.

75. Kumar R, Ooi C, Nicoll A. Anal incontinence and quality of life
following obstetric anal sphincter injury. Arch Gynecol Obstet.
2012;285(3):591-7.

76. Nordenstam J, Altman D, Brismar S, Zetterstrom J. Natural
progression of anal incontinence after childbirth. Int Urogynecol J
Pelvic Floor Dysfunct. 2009;20(9):1029-35.

77. Poen AC, Felt-Bersma RJ, Cuesta MA, Meuwissen GM. Vaginal
endosonography of the anal sphincter complex is important in the
assessment of faecal incontinence and perianal sepsis. Br J Surg.
1998;85(3):359-63.

78. Sangalli MR, Floris L, Faltin D, Weil A. Anal incontinence in women
with third or fourth degree perineal tears and subsequent vaginal
deliveries. Aust N Z J Obstet Gynaecol. 2000;40(3):244-8.

79. Sze EH. Anal incontinence among women with one versus two complete
third-degree perineal lacerations. Int J Gynaecol Obstet.
2005;90(3):213-7.

80. Sze EH. Prevalence and severity of anal incontinence in women with
and without additional vaginal deliveries after a fourth-degree perineal
laceration. Dis Colon Rectum. 2005;48(1):66-9.

81. Walker HJ, Gelman W, Thomas JM, Bearn PE, McWilliams D. Does vaginal
delivery after Obstetric Anal Sphincter Injury (OASI) cause further
damage? International Urogynecology Journal and Pelvic Floor
Dysfunction. 2009;20:S278-9.

82. Bondili A, Siddiqui I, Nichols W, Kettle C, Cooper J, O'mahony F, et
al. Management of pregnancies following third and fourth degree perineal
tears: A multi disciplinary approach. International Urogynecology
Journal and Pelvic Floor Dysfunction. 2011;22:S120-1.

83. Sideris M, McCaughey T, Hanrahan JG, Arroyo-Manzano D, Zamora J, Jha
S, et al. Risk of obstetric anal sphincter injuries (OASIS) and anal
incontinence: A meta-analysis. Eur J Obstet Gynecol Reprod Biol.
2020;252:303-12.

84. Narice BF, Marks K, Jha S. Factors that influence pregnant women's
decision on mode of delivery after previous obstetric anal sphincter
injury. Eur J Obstet Gynecol Reprod Biol. 2023;281:32-5.

\section*{Figure and table legends}

{\label{figure-and-table-legends}}

Figure 1: ROBINS Risk of bias assessment tool for studies included in
meta-analysis for the primary outcome

Figure 2: Index and recurrent OASI rates across included studies

Figure 3: Anal incontinence and mode subsequent birth after OASI

Figure 4: Total incidence of anal incontinence after subsequent birth

Table S1: Characteristics of included studies

S2: Study inclusion and exclusion criteria

S3: Prisma diagram

S4: Description of studies included for primary outcome

S5: Recurrent OASI rates across all studies

S6: Meta-analysis for secondary AI outcomes (1) solid (2) liquid (3)
flatus (4) urgency

S7: Satisfaction, regret and QOL after subsequent birth

S8: Subsequent birth vs no subsequent birth after OASI

S9: Incidence of AI pre- and post- subsequent birth; paired data

\section*{Primary Figures}

{\label{primary-figures}}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Figure 1: ROBINS Risk of bias assessment tool for studies included
meta-analysis for the primary outcome

Figure 2: Index and recurrent OASI rates across included studies\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
\textbf{rOASI population} & \textbf{No studies} & \textbf{Index OASI
rate (\%)} & \textbf{rOASI rate (\%)} & \textbf{rOASI range
\%}\tabularnewline
\midrule
\endhead
\textbf{All studies} & 49 & 3.31 & 6.6 & 1.9-25\%\tabularnewline
\textbf{National/state database} & 12 & 4.34 & 5.59 &
2.1-7.2\%\tabularnewline
\textbf{Teaching/university hospital} & 32 & 6.13 & 6.02 &
1.9-13.4\%\tabularnewline
\textbf{District general hospital} & 6 & 3.2 & 11.74 &
6.66-25\%\tabularnewline
\bottomrule
\end{longtable}

Figure 3: Anal incontinence and mode subsequent birth after OASI

A New or worsening AI after subsequent birth- all time periods\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

B New or worsening AI after subsequent birth- short term (3 months-2
years)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

C New or worsening AI after subsequent birth- long term ([?] 5 years)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

D AI in asymptomatic women after subsequent birth, all time periods\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

Figure 4: Total incidence of anal incontinence after subsequent birth\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

\textbf{Hosted file}

\verb`Figure 1 ROBINS ROB summary graph.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`Figure 2 rOASI .docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`Figure 3- Incidence of AI after subsequent birth.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`Figure 4 Total incidence of AI after SB (VD&amp;CS).docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`Table S1 Characteristics of included studies .docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S2 Inclusion &amp; Exclusion criteria.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S3 Prisma diagram.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S4 Description of included studies for primary outcome.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S5 Recurrence of OASI rates, all data.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S6 solid, liquid, flatal, fecal urgency.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S7 satisfaction, regret and QOL.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S8 subsequent birth vs no subsequent birth.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\textbf{Hosted file}

\verb`S9 Incidence of anal incontinence pre- vs post- subsequent birth.docx`  available at \url{https://authorea.com/users/698051/articles/685902-is-cesarean-section-protective-against-anal-incontinence-in-women-after-obstetric-anal-sphincter-injury-oasi-a-systematic-review-and-meta-analysis}

\selectlanguage{english}
\FloatBarrier
\end{document}

