Premature delivery in diabetes: etiology and risk factors

Preterm birth is the leading cause of perinatal morbidity and mortality, while preterm labor and delivery in diabetes mellitus (DM) carries an increased risk of perinatal complications. We investigated the hypothesis that DM (gestational and pregestational) is an independent risk factor for preterm birth and evaluated the hypothesis that the risk factors for preterm birth in diabetics are different from those in non-diabetics. The study population consisted of all singleton deliveries at this hospital between 1990-1997. Excluded were those of mothers who had not had prenatal care, or who had only partial care or multiple gestations. There were 3 subgroups: 834 women with pregestational DM, 3,841 with gestational DM, and 66,253 non-diabetics. The combined spontaneous and induced preterm delivery rate was determined in each subgroup. Potential risk factors for spontaneous preterm deliveries were assessed by a univariate model. A logistic regression model was used to assess the unique contribution of DM (gestational and pregestational) to preterm delivery in the presence of the other risk factors, and to compare risk factors for preterm delivery between subgroups. The prevalence of spontaneous preterm delivery was: 7.1% in non-diabetics, 10.0% in those with gestational DM and 25.5% in those with pregestational DM. When adjusted by a multivariate model for other risk factors for preterm delivery, DM still remained an independent risk factor for spontaneous preterm delivery (gestational DM: odds ratio 1.28, 95% CI: 1.1-1.48; pregestational diabetes: odds ratio 3.4, 95% CI: 2.65-4.36). The main difference in risk factors for preterm birth between the 3 subgroups was the amount of amniotic fluid. Polyhydramnios was an independent risk factor for preterm delivery in non-diabetics and in pregestational DM, but not in gestational DM. On the other hand, oligohydramnios was associated with a higher risk for preterm delivery only in gestational DM compared to non-diabetics. DM (gestational and pregestational) is an independent risk factor for spontaneous preterm delivery. Polyhydramnios is an independent risk factor for preterm delivery in pregestational but not in gestational DM. Oligohydramnios is a greater risk factor for preterm delivery in gestational DM compared to non-diabetics.