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

BACKGROUND: Pre-eclampsia and placental abruption may share a common pathophysiologic mechanism, namely, uteroplacental ischaemia. The aim of this study was to investigate the association between placental abruption and risk of pre-eclampsia in a subsequent pregnancy, and to determine whether the association differs by the gestational age at the time of abruption.

METHODS: A nested case-control study among multiparous women in the Medical Birth Register of Finland from 1996-2010 was conducted. Cases of pre-eclampsia (n = 6487) and frequency matched controls (n = 25,948) were linked to the Hospital Discharge Registry to ascertain data on prior abruption. Abruption was categorised as preterm (<37 weeks) or term (≥37 weeks) based on the gestational age at delivery. We fit logistic regression models to evaluate the associations between abruption and the odds of pre-eclampsia in the subsequent pregnancy before and after adjusting for potential confounders.

RESULTS: Preterm abruption was associated with over a twofold increase in risk of pre-eclampsia [odds ratio (OR) 2.2, 95% confidence interval (CI) 1.5, 3.3] in a subsequent pregnancy. In contrast, term abruption was not associated with pre-eclampsia (OR 1.1, 95% CI 0.7, 1.7). The association between preterm abruption and pre-eclampsia was further elevated among women with a history of pre-eclampsia. Associations with preterm abruption were also strengthened when the outcome was pre-eclampsia with early delivery (<34 weeks).

CONCLUSIONS: These findings suggest that placental abruption in a prior pregnancy is associated with a different risk profile of pre-eclampsia based on the gestational age of the abruption-affected pregnancy.