title: Factors affecting the duration of the latency period in preterm premature rupture of membranes.
abstract: OBJECTIVE
  To investigate the natural course of preterm premature rupture of membranes (PPROM) at <34 + 0 weeks and to identify factors that affect the duration of the latency period.
  
  
  METHODS
  A retrospective cohort study of all women diagnosed with PPROM prior to 34 + 0 weeks during 1998-2006. Latency period was defined as the time between onset of PPROM to either spontaneous delivery, labor induction at 34 + 0 weeks, or indicated delivery prior to 34 + 0 weeks because of suspected chorioamnionitis or nonreassuring fetal heart rate.
  
  
  RESULTS
  The overall rate of PPROM was 1.4% (905/66,775), of which 46% (417/905) occurred at <34 + 0 weeks. Overall, the latency period exceeded 48 h in about 73.4% of cases (306/471). Women with short latency periods (<48 h) were characterised by higher degree of cervical dilatation and higher gestational age at admission and were more likely to be nulliparous. The duration of the latency period ranged between 0 and 59 days and was inversely related to gestational age at admission (r = -0.63, P < 0.001). Using Cox proportional hazards model, gestational age at admission (HR = 1.29, 95% CI = 1.22-1.37), oligohydroamnios (HR = 1.49, 95% CI = 1.18-1.87), cervical dilatation >1 cm (HR = 0.65, 95% CI = 0.52-0.83), fetal growth restriction (HR = 2.94, 95% CI = 1.24-6.94) and nulliparity (HR = 1.28, 95% CI = 1.12-1.63) were significantly associated with shorter duration of the latency period.
  
  
  CONCLUSIONS
  In this study, we have identified several predictive factors for the duration of the latency period in cases of PPROM. This information may assist clinicians in risk stratification and in providing consultation for women presenting with PPROM prior to 34 weeks of gestation.
authors.affiliation: Helen Schneider Hospital for Women, Rabin Medical Center, Petach Tikva, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. nirm@clalit.org.il
authors.forename: Nir
authors.initials: N
authors.lastname: Melamed
authors.forename: Eran
authors.initials: E
authors.lastname: Hadar
authors.forename: Avi
authors.initials: A
authors.lastname: Ben-Haroush
authors.forename: Boris
authors.initials: B
authors.lastname: Kaplan
authors.forename: Yariv
authors.initials: Y
authors.lastname: Yogev
mesh_terms: D000037:Abruptio Placentae / Q000453:epidemiology; D000328:Adult; D002821:Chorioamnionitis / Q000453:epidemiology; D015331:Cohort Studies; D036861:Delivery, Obstetric; D005260:Female; D005317:Fetal Growth Retardation / Q000453:epidemiology; D005322:Premature Rupture of Fetal Membranes / Q000453:epidemiology*; D005865:Gestational Age; D006801:Humans; D007747:Labor Stage, First; D016104:Oligohydramnios / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D013997:Time Factors