Factors affecting the latency period in patients with preterm premature rupture of membranes

The objective of the study was to assess the factors affecting the latency period in woman with preterm premature rupture of membranes (PPROM) and evaluate morbidity associated with prolonged latency.

A population-based retrospective study including all women with PPROM (prior to 37 weeks' gestation) during the years 1998-2008 was conducted. Comparison of the latency period was conducted by the Mann-Whitney U test since the latency period was not normally distributed (most delivered in 24 h). Multivariable logistic regression model was constructed to find independent factors associated with prolonged latency period (>72 h).

During the study period, there were 1,399 singleton deliveries of patients with PPROM; 24.6% (345) occurred prior to 34 weeks' gestation. The duration of the latency period was significantly longer among woman with PPROM before 34 weeks as compared to PPROM after 34 weeks' gestation (5.78 vs. 2.02 days; p < 0.001). Other factors associated with longer latency period were multiparity (more than one previous delivery) and maternal age >35. Using a multivariable analysis, the following factors were significantly associated with latency period >72 h: lower gestational age (weeks, OR = 0.8, 95% CI 0.77-0.84; p < 0.001) and multiparity (OR = 1.7, 95% CI 1.3-2.2; p < 0.001). Prolonged latency period (>72 h) was significantly associated with chorioamnionitis (OR = 2.095, 95% CI 1.44-3.04; p < 0.001) and oligohydramnios (OR = 3.041, 95% CI 1.43-6.45; p = 0.004) but not with placental abruption (OR = 0.854, 95% CI 0.41-1.78; p = 0.674) or perinatal mortality (OR = 1.2, 95% CI 0.6-2.2; p = 0.556).

The duration of the latency period is inversely associated with gestational age. Nulliparity is associated with lower latency period. Prolonged latency is a significant risk factor for chorioamnionitis.