Document Type : Research articles


1 Department of Biostatistics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, IR Iran

2 Department of Pediatrics, Mazandaran University of Medical Sciences, Mazandaran, IR Iran


Background: The effectiveness of cervical cerclage (CC) in mothers suffering cervical incompetence (CI) for preventing preterm birth (PTB) in twin gestations remains controversial. Some studies show that it plays a preventive role in the occurrence of PTB, while others suggest it is ineffective.
Objectives: Our aim was to evaluate the effectiveness of CC in preventing PTB and negative neonatal outcome (e.g., respiratory distress syndrome (RDS) and birth weight) based on a new statistical framework: multilevel analysis and propensity score matching (PSM) in twin pregnancies.
Methods: A cross-sectional study was conducted in the maternity wards of three general and teaching hospitals in Tehran, Iran, during January 2014 to February 2015. Using stratified random sampling with the proportional allocation method, twin pregnancies
were randomly selected from the medical files list. Of 431 eligible individuals, 31 patients underwent CC as a result of CI, and the others had healthy cervixes and no CC. Next, variables that confound the relationships between CC and PTB (e.g., assisted reproductive technology (ART), preterm rupture of membrane (PROM), nulliparous, history of abortion, and mother’s age) by applying 1:2 PSM were matched in both groups. The CC group was considered the case group and, based on PSM, 61 patients, whose characteristics were similar to the CC group, were selected from 400 healthy mothers as a control group. For considering twins dependencies, multilevel modeling was used, and prevalence of PTB, LBW, and RDS, as well as mean gestational age in the two groups, were compared.
Results: The standardized mean difference (SMD) shows that the distribution of confounding variables in the propensity-matched data is the same in both groups. Results revealed that, although gestational age in the case group was significantly less than the control group, the prevalence of PTB in case and control was not significantly different (P = 0.190). The prevalence of neonatal outcome of RDS and LBW in the case and control groups was not significant (P > 0.05).
Conclusions: It appears that CC has an effective role in prevention of PTB, LBW, and RDS, because their prevalence in both groups was the same. However, drawing a clear conclusion regarding its role requires more research with a random clinical trial (RCT) design.