Several studies have suggested that preterm delivery is related to a risk of subsequent ischaemic heart disease (IHD) in the mother. We conducted a nested case-control study in the E3N cohort to assess the association between preterm delivery of a first child and IHD, and the effect of major cardiovascular risk factors on this association. The study included 109 cases and 395 controls. Mothers who had preterm delivery were at an increased risk of IHD [multivariate hazard ratio 2.09 (95% confidence interval 1.07-4.09)]. This association was independent of major cardiovascular risk factors.