Identifying the associated factors with onset of preterm PROM compared with term PROM - A retrospective cross-sectional study.

Objective: To determine the risk factors associated with the preterm premature rupture of membranes (p-PROM).

Materials And Methods: This retrospective cross-sectional study assessed 110 p-PROM cases from among 6642 deliveries at a Japanese perinatal medical center, from June 2016 to September 2018. The control group comprised 220 term PROM (t-PROM) cases. We excluded cases with artificial PROM or rupture of membranes after labor, those with multiple pregnancies, those with p-PROM at 36 weeks and those with t-PROM at 37 weeks. In order to compare p-PROM with t-PROM, univariate and multivariate analysis were performed using several clinical factors at the time of PROM onset.

Results: The p-PROM group included 110 cases with 14-35 weeks PROM, and the t-PROM group included 220 cases with 38-41 weeks PROM. Eleven factors were identified as significant factors on the univariate analysis. A history of cervical conization (OR 37.5, 95% CI: 2.31-607.1), cervical length <25 mm at 28 weeks (OR 9.31, 95% CI: 1.76-49.3), negative Lactobacillus (OR 4.01, 95% CI: 1.18-13.7), and bleeding during the second trimester (OR 3.35, 95% CI: 1.18-9.53) were identified as significant factors by the multivariate analysis. Based on the risk factors identified during the multivariate analysis, we divided the 330 cases in the following three groups: 0 group (n = 244), 1 group (n = 60), and 2-4 group (n = 26). The ratio of p-PROM:t-PROM was calculated and compared for each group. The ratios were 21% (0 group), 57% (1 group), and 100% (2-4 group), indicating statistically significant differences between the groups (p < 0.001).

Conclusion: We found that the following four factors were associated with p-PROM: history of cervical conization, cervical length <25 mm at 28 weeks, negative Lactobacillus, and bleeding during the second trimester. Our results suggest that we can identify patients who are at increased risk for p-PROM, based on these factors. Further research is necessary to determine the optimal treatment approach for these patients to prevent p-PROM.