Factors Affecting The Duration Of The Latency Period In Preterm Premature Rupture Of Membranes

Objective To investigate factors that affect the duration of the latency period of preterm premature rupture of membranes (PPROM).Methods A retrospective cohort study was conducted of 108 pregnant women with a diagnosis of PPROM prior to 34 weeks of gestation at department of Obstetrics and Gynecology, The First Affiliated Hospital of Chongqing Medical University from Jan. 2005 to Aug. 2009. Patients were devided into three groups: (1) group of latency period <48 h; (2) group of latency period from 48h to 7d; (3) group of latency period >7d. Ench groups were controlled for patient's age, gestational age of PPROM and delivery, parity, singleton/twins, oligohydroamnios, fetal growth restriction(FGR), cervical dilatation at admission and cervical length at admission.Results (1)Group of latency period <48h had significantly a higher gestational age of PPROM, with a shorter non-hospital stay compared with other two groups (P<0.05). Group of latency period <48 h were characterised by higher degree of cervical dilatation and shorter cervical length (P<0.05). (2)Group of latency period <48 h had a higher rates of multiparous(39.5%), twins(39.5%), oligohydroamnios(50.9%), FGR(18.4%) than those in group of latency period from 48h to 7d (19.6%, 11.1%, 39.2%, 7.8%) and group of latency period >7d(5.3%, 5.3%, 29.1%, 5.3%), P<0.05. (3)Using Cox proportional hazards model, gestational age of PPROM (HR=1.59, 95%CI= 1.34- 1.89), twins (HR=1.97, 95%CI=1.21-3.22), multiparous (HR=1.73, 95%CI=1.03-2.89), oligohydroamnios (HR=2.12, 95%CI=1.36-3.29), fetal growth restriction (HR=2.24, 95%CI=1.18-4.26), cervical dilatation at admission (HR=1.29, 95%CI=1.02-1.63), and cervical length at admission (HR=0.96, 95%CI=0.93-0.98) were significantly associated with shorter duration of the latency period (P<0.05).Conclusion In this study, we have identified several predictive factors including gestational age of PPROM, parity, singleton/twins, oligohydroamnios, FGR, cervical dilatation at admission and cervical length at admission that influenced the duration of the latency period in cases of PPROM.