Objective: The purpose of this study was to identify risk factors for second trimester premature preterm rupture of membranes or advanced cervical dilation in a high-risk population. Study design: A retrospective case control study was performed that compared women with premature preterm rupture of membranes or advanced cervical dilation to term control subjects.The cases included all singleton pregnancies between 14 and 24 weeks of gestation with premature preterm rupture of membranes or advanced cervical dilation between 1996 and 2000.The next 2 term deliveries were chosen as control subjects.The variables compared between cases and control subjects included pregnancy history, infectious and medical histories,cervical/uterine procedures, and habits. This study had institutional review board approval. Results: There were 102 women with premature preterm rupture of membranes, 56 women with advanced cervical dilation, and 316 control subjects. The meangestational ages for premature preterm rupture of membranesor advanced cervical dilation were 20 ± 2.6 and 19.9 ± 2.6 weeks. Tobacco use, history of or current cervical incompetence,previous second trimester delivery, previous termination at < 20 weeks of gestation, and previous premature preterm rupture of membranes were associated significantly with premature preterm rupture of membranes or advanced cervical dilation compared with term control subjects. When controlled for parity, age,marital status, and race, these variables remained significant. Bacterial vaginosis in current pregnancy was associated significantly with only advanced cervical dilation but not premature preterm rupture of membranes compared with control subjects. A history of Chlamydia was most common in the term control subjects (19.6% ). Conclusion: In a high-risk population of inner city women, only pregnancy history and tobacco use distinguished women with second trimester premature preterm rupture of membranes or advanced cervical dilation from term control subjects. No infectious risk factors distinguished control women from women with premature preterm rupture of membranes. The only modifiable risk identified was tobacco use. Objective: The purpose of this study was to identify risk factors for second trimester premature preterm rupture of membranes or advanced cervical dilation in a high-risk population. Study design: A retrospective case control study performed performed women compared with premature preterm rupture of membranes or advanced cervical dilation to term control subjects. The cases included all singleton pregnancies between 14 and 24 weeks of gestation with premature preterm rupture of membranes or advanced cervical dilation between 1996 and 2000.The next 2 term deliveries were chosen as control subjects. The variables compared between cases and control subjects included pregnancy history, infectious and medical histories, cervical / uterine procedures, and habits. This study has institutionalized board approval. , and 316 control subjects. The meangestational ages for premature pret erm rupture of membranesor advanced cervical dilation were 20 ± 2.6 and 19.9 ± 2.6 weeks. Tobacco use, history of or current cervical incompetence, previous second trimester delivery, previous termination at <20 weeks of gestation, and previous previous rumen preterm rupture of membranes were associated significantly with premature preterm rupture of membranes or advanced cervical dilation compared with term control subjects. When controlled for parity, age, marital status, and race, these variables remained significant. Bacterial vaginosis in current pregnancy was associated significantly with only advanced cervical dilation but not premature rupture of membranes compared with control subjects. A history of Chlamydia was most common in the term control subjects (19.6%). Conclusion: In a high-risk population of inner city women, only pregnancy history and tobacco use distinguished women with second trimester premature rupture of membranes or advanced cervical dilation from term control subjects. No infectious risk factors distinguished control women from women with premature preterm rupture of membranes. The only modifiable risk identified was tobacco use.