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.