Objective: Preterm delivery has been shown to be associated with subsequent maternal cardiovascular morbidity. However, the impact of the severity and recurrence of preterm delivery on the risk of specific cardiovascular events and the metabolic syndrome in the mother, have not been investigated.

Design: National registry-based retrospective cohort study.

Setting: Women delivering in Denmark from 1978 to 2007.

Population: Women with a first singleton delivery (n = 782 287), and with a first and second singleton delivery (n = 536 419).

Methods: Cox proportional hazard models, with the gestational age stratified into four groups as primary exposure. We made adjustments for maternal age, year of delivery, hypertensive pregnancy disorders, fetal growth deviation, placental abruption and stillbirth.

Main outcome measures: Subsequent maternal hypertension, ischaemic heart diseases, thromboembolism and type-II diabetes.

Results: After a first delivery at 32-36 completed weeks of gestation, the adjusted risk of subsequent type-II diabetes increased 1.89-fold (1.69-2.10) and the risk of thromboembolism increased 1.42-fold (1.24-1.62). Women having a preterm delivery in the first pregnancy and a term delivery in the second had a 1.58-fold (1.34-1.86) increased risk of type-II diabetes and a 1.18-fold (0.96-1.44) increased risk of thromboembolism. Women having two preterm deliveries had a 2.30-fold (1.71-3.10) increased risk of type-II diabetes and a 1.80-fold (1.29-2.50) increased risk of thromboembolism.

Conclusions: Preterm delivery is independent of other pregnancy complications associated with subsequent maternal overt type-II diabetes and thromboembolism. The recurrence of preterm delivery will augment these risks.