Previous pregnancy outcomes and subsequent risk of preterm rupture of amniotic sac membranes.

OBJECTIVE

To test the hypothesis that previous unfavourable pregnancy outcomes increase the risk for premature birth, with (PP) or without (PTB) premature rupture of the amniotic sac (PROM) at the index pregnancy and that multiple undesirable outcomes increase risk.

DESIGN

Case control study.

SETTING

Two university hospitals.

SUBJECTS: Four hundred sixty-three women aged 15 to 45 years who were delivered preterm PROM, full term PROM and preterm without PROM matched with 463 women who delivered full term. All women included in the study had at least one previous pregnancy.

OUTCOME MEASURES: Odds ratio of previous adverse pregnancy outcome among index cases.

RESULTS

Compared with controls, PP cases had odds ratios of 95 for previous preterm birth, 186 for abortion and prematurity and 158 for fetal loss, abortion/prematurity after controlling for confounding variables. Compared with controls, PTB cases had an odds ratio of 96.5 for previous preterm delivery, 84 for abortion and prematurity, and 320 for fetal loss/abortion and prematurity after controlling for confounding variables.

CONCLUSIONS

Previous preterm delivery, abortion and prematurity and fetal loss/abortion and prematurity all increase risk for subsequent preterm birth with or without PROM.