Risk factors for preterm premature rupture of the fetal membranes.

Preterm premature rupture of the membranes (PPROM) is a significant cause of prematurity, accounting for approximately one third of preterm births in the United States. PPROM occurs in approximately 0.7-2% of all pregnancies nationally, and has a reported recurrence rate of 21%. The elucidation of potential risk factors for PPROM could contribute to a better understanding of its etiology. To study the contributions of 20 potential risk factors, we undertook a case-control study in our clinic population, which has a 5-6% incidence of PPROM. One hundred and thirty-three patients experiencing PPROM were matched for race, age, parity and gestational age with undelivered patients. Studies performed included ultrasonographic examinations, blood levels of ascorbic acid and zinc, microbiologic assays, patient questionnaires, and chart reviews. After stratification of both groups into subgroups based on matching criteria, summary tests of significance and Mantel-Haenszel tests of odds ratios were performed. On univariate analysis the following factors achieved significance at the p less than 0.05 level with 95% confidence intervals: 1) previous history of PPROM 2) smoking (dose related) 3) fundal location of the placenta in the present pregnancy. 4) a prior history of cerclage. After regression analysis, we concluded that smoking and history of previous PPROM were found to be risk factors for PPROM in our inner city black population.