Interpretation
Systematic reviews are considered the highest level of evidence
regarding the efficacy, effectiveness and safety of prophylactic or
therapeutic interventions and play a significant role in guiding health
policy, best practices, and evidence-based patient care. However, our
quality assessment of the articles reviewed herein found that many did
not utilize rigorous methodological approachs when conducting the
studies. Thus the introduction of different biases that can confound
conclusions and hinder policymaking, ultimately affecting patient-care
cannot be excluded.
A moderate level of heterogeneity in the quality assessment of published
systematic reviews involving the efficacy, effectiveness and safety of
methods for the induction of labour was identified in our assessment
with AMSTAR scores ranging from 3 to 9. The number of systematic reviews
on this topic has increased over the past decade, with the most (n=11)
being published in 2019. However, no significant improvement in
methodological quality was found. This observation diverges from other
areas in medicine, like critical care and radiology, in which an
improvement in methodological quality of systematic reviews has been
demonstrated over time56, 57. Thus, results of our
AMSTAR assessment of the published systematic reviews revealed a need
for greater scientific rigour in the study of the induction of labour.
Systematic reviews funded by hospitals, institutions, philanthropists,
government grants or with unreported funding had no difference in
methodological quality according to the AMSTAR Checklist (p=0.34). Our
findings report that only 36 (75%) of the 48 studies evaluated in our
assessment included a conflict of interest statement in both the
systematic review and the studies included therein and thus criterion 11
of the AMSTAR Checklist was not satisfied. We suggest this particular
weakness in the literature is concerning as there is a need for
transparent reporting of conflicts of interest to allow for the
judgement of any external influences on study conclusions. The effect of
this potential bias is increased in studies that do not have an
established a priori protocol where redefined outcome measures
and post-hoc analysis could further exacerbate a biased perspective of
the evidence. Our findings indicated that 40 of 48 articles (83%) used
an a priori study design (AMSTAR criterion #1).
No significant correlation was observed between AMSTAR score and the
journal impact factor, suggesting that leading journals may not
necessarily evaluate methodological quality more rigorously than others.
However, articles from the Cochrane Database of Systematic
Reviews on average, score higher on the AMSTAR Checklist than articles
from other peer-reviewed journals (p=0.01). This finding supports the
generally accepted position that the methods followed by the Cochrane
Collaboration sets the highest standard for conducting and publishing
systematic reviews. Consistent findings regarding the quality of
Cochrane reviews has also been reported for other medical disciplines as
well58.
In the present assessment, there was no significant correlation between
AMSTAR score and total citations. We sugges that this finding may
indicate that authors who utilize systematic reviews to support their
findings or hypotheses do not critically evaluate the quality of the
studies cited. This is of particular importance if these systematic
reviews are being used to generate or refute medical hypotheses.
The highest AMSTAR score of 9/11 was recorded for several Cochrane
Collaboration publications (n=7). Three examined the use of
oxytocin9,11,14, three others examined mechanical
methods of labour induction17,21,47, and one examined
the use of mifepristone26. An AMSTAR point for a
comprehensive literature search could not be provided for some of these
reviews9,11,17,21,26. However,
some17,26,47 included grey literature such as evidence
from the Cochrane Pregnancy and Childbirth Group’s Trials Register and
clinicaltrials.gov which captures data that has not been peer reviewed.
All seven high ranking articles also conducted quality assessments of
the included studies, which satisfy AMSTAR criteria that we believe to
be of greater importance. Important conclusions from these seven studies
that scored the highest on the AMSTAR criteria include that a balloon
catheter may be less effective than oral misoprostol but have a greater
safety
profile17.
The use of a balloon catheter is likely as effective as the use of
intravaginal prostaglandin E2 when inducing
labour17. Oxytocin was suggested to be less effective
in achieving vaginal birth within 24 hours compared to prostaglandin
agents9.
High-dose oxytocin (100mU in the first 40 minutes, rising above 600 mU
in the first two hours) compared with low-dose oxytocin (below 100mU in
the first 40 minutes, rising to below 600 mU in the first two hours) has
been shown to increase the risk of uterine hyperstimulation without
increasing the rate of vaginal delivery within 24
hours14. However, discontinuing IV oxytocin
stimulation after the active phase of labour may reduce the risk of a
caesarean
delivery11.
Another
study26concluded that the literature is inadequate to draw conclusions that
mifepristone helps induce labour. It is also suggested that the use of
membrane sweeping does not provide clinical benefit and that this labour
induction method should be balanced against women’s
discomfort21.
Finally, one study concluded that there was no clear benefit from using
acupuncture or acupressure in reducing the rate of caesarean
section47.