Strengths and Limitations
This is the first NMA including a study with the combined intervention
pessary + vaginal progesterone and, despite the small subgroup sample
size, the interesting reduction results for PTB and sPTB<34
illustrates the lack amid RCT involving combined interventions and
highlights the need for new trials adequately powered to strength the
results.
In limitations, this NMA includes a large number of studies and
different cervical length cutoff points create heterogeneity among
included studies. Moreover, we used 40mm as a cervical length cut off
point to identify a mid-trimester short uterine cervix, considering
previous studies that identified a similar measure for the 25th
percentile of uterine cervix in twins39. It allowed us
to include a large number of patients in the control group when we had
access to previous IPD meta-analysis data. However, it was not possible
for all studies, which we also consider a limitation in our research.
In women with multiple gestation and a short cervical length, neither
progesterone, cerclage or cervical pessary achieved a statistically
significant reduction in sPTB<34 or PTB<34 weeks.
More trials are needed to identify whether treatment is effective.