Placental abruption and subsequent risk of pre-eclampsia: a population-based case-control study.

Preeclampsia is one of three conditions that constitute the syndrome of ischaemic placental disease (IPD), a group of pathologies that also includes placental abruption and intrauterine growth restriction.1 A common aetiology involving poor placentation in early pregnancy has been proposed as an underlying mechanism leading to the characteristic uteroplacental underperfusion or ischaemia in these obstetrical complications.2 IPD in a prior pregnancy is a risk factor for IPD in a subsequent pregnancy.3,4 While recurrence patterns of IPD have been well documented, little is known about the recurrence of such diseases based on the gestational age at delivery (i.e., preterm versus term gestations). Recent evidence suggests that the causative pattern of IPD may differ with respect to preterm and term gestations, with the underpinnings of ischaemic placental diseases being more homogeneous at preterm than term gestations.1 In the United States the prevalence of abruption is 2.3% among preterm deliveries (<37 weeks) and 0.3% among term deliveries, making preterm abruption nine times more common.5 One study found that mean birthweight and placental weights were lower in preterm abruption births compared to preterm non-abruption births, but among term abruption births no such association was observed, indicating that preterm abruption is more consistent with uteroplacental ischaemia.6 Placental abruption in a prior pregnancy is associated with an approximate two-fold increase in the risk of preeclampsia in a subsequent pregnancy.3 It is not known if a different risk is conferred based on gestational timing of the abruption. The aim of this study is to explore the association of placental abruption on the subsequent risk of preeclampsia and determine if this association differs between preterm and term abruptions.