Preterm delivery in women with pregestational diabetes mellitus or chronichypertension relative to women with uncomplicated pregnancies

OBJECTIVE: The purpose of this study was to compare the rates of indicated and spontaneous preterm delivery among women with chronic hypertension or p regestational diabetes mellitus with the rates among healthy women. STUDY DESIGN: This was a secondary analysis of data from healthy women with singleton gestations enrolled in a prospective observational study for pre diction of preterm delivery (control group, n = 2738), women-with pregestat ional diabetes mellitus requiring insulin therapy (n = 461), and women with chronic hypertension (n = 761). The two latter groups were enrolled in a r andomized multicenter trial for prevention of preeclampsia. The main outcom e measures were rates of preterm delivery, either spontaneous (preterm labo r or rupture of membranes) or indicated (for maternal or fetal reasons), an d neonatal outcomes. RESULTS: The overall rates of preterm delivery were significantly higher am ong women with diabetes mellitus (38%) and hypertension (33.1%) than among control women (13.9%). Rates were also significantly higher for delivery at <35 weeks' gestation. Women with diabetes mellitus had significantly highe r rates of both indicated preterm delivery (21.9% vs 3.4%; odds ratio, 8.1; 95% confidence interval, 6.0-10.9) and spontaneous preterm delivery (16.1% vs 10.5%; odds ratio, 1.6, 95% confidence interval, 1.2-2.2) than did women in the control group. In addition, they had significantly higher rates of both indicated preterm delivery (odds ratio, 4.8; 95% confidence interval, 3.0-7.5) and spontaneous preterm delivery (odds ratio, 2.1;95% confidence i nterval, 1.4-3.0) at <35 weeks' gestation than did control women. Compared with control women those with chronic hypertension had higher rates of indi cated preterm delivery at both <37 weeks' gestation (21.9% vs 3.4%; odds ra tio, 8.1; 95% confidence interval, 6.2-10.6) and at <35 weeks' gestation (1 2.1% vs 1.6%; odds ratio, 8.2; 95% confidence interval, 5.7-11.9), but ther e were no differences in rates of spontaneous preterm delivery. CONCLUSION: The increased Fate of preterm delivery among women with chronic hypertension relative to control women was primarily an increase in indica ted preterm delivery, whereas the rates of both spontaneous and indicated p reterm delivery were increased among women with pregestational diabetes mel litus.