Data Analysis
For studies with consecutive enrolment and where data was presented on
the planned mode and actual mode of delivery for all subjects, we
calculated the median TOLAC rate and median VBAC rate across studies,
using frequency weights for study sample size. The primary clinical
outcome assessed was uterine rupture. Secondary outcomes were maternal
mortality and perinatal (stillbirth and neonatal) mortality. We
estimated the overall rate of these adverse outcomes across all births
for which this data was available to generate estimates across all
available studies, also weighted for study sample size. We further
compared uterine rupture rate, maternal mortality and perinatal
mortality (stillbirth and neonatal mortality) between TOLAC and ERCS in
studies where comparison groups were available and calculated the pooled
odds ratios of adverse outcomes with 95% confidence intervals. For this
comparison, a random-effects model was used to combine the studies while
accounting for heterogeneity. We used forest plots to graphically
summarise the pooled results. We performed sensitivity analyses using
studies with a MINORS score of ≥16.
We performed subgroup analyses to evaluate TOLAC and VBAC rates over
time and compared rates in studies published before and after January
1st, 1996 using the rank-sum test to assess for differences by region
and changing practice patterns and trends. We choose 1996, as a
comparison date as the last published metanalysis of TOLAC in SSA
included studies up to 1995.10 This year also
corresponds to a period when a marked decline in the rates of TOLAC and
VBAC was seen in the other regions of the world due to emerging data on
risks of uterine rupture following trial of labour.13
All statistical calculations were performed with STATA, version 13
(StataCorp, College Station, TX USA).