Background: Gestational diabetes is a precursor to type 2 diabetes. Little is known about the relation of other common pregnancy complications, such as preterm birth, to risk of type 2 diabetes.
Methods: We assessed preterm birth in relation to incident type 2 diabetes among 31,101 participants from the Black Women's Health Study. Preterm birth, defined as <37 weeks gestation, was reported at baseline (1995) and on subsequent biennial follow-up questionnaires. Self-reported type 2 diabetes diagnoses were ascertained on biennial questionnaires through 2009. We used Cox proportional hazards models to calculate incidence rate ratios (IRRs) and 95% confidence intervals (CIs), adjusting for potential confounders.
Results: At baseline, 5162 participants (19%) reported a history of giving birth preterm, of which 16% occurred at <32 weeks gestation. A total of 3261 cases of type 2 diabetes were ascertained during follow-up. Ever having had a preterm birth was associated with a 20% increased risk (95% CI = 1.11-1.31) after adjusting for age at first birth, family history of diabetes, education, respondent having been born preterm, and body mass index. Gestational age <32 weeks was associated with the greatest risk (IRR = 1.27 [95% CI = 1.06-1.51]). Among women without a history of gestational diabetes, the IRR for type 2 diabetes among women who ever had a preterm birth was 1.17 (1.07-1.28).
Conclusion: Preterm birth was associated with an increased type 2 diabetes risk in black mothers, independent of gestational diabetes.