Results
2472 studies were identified. 86 studies met inclusion criteria after
full text review (PRISMA diagram S3).
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, 4th degree tear or EAUS defects), and
methodological limitations (e.g. retrospective service evaluation,
follow-up questionnaire with limited response rate).
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 ≥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.
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).
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).