Recurrence risk of a delivery before 34 weeks of pregnancy due to an early onset hypertensive disorder: a systematic review.

Early onset hypertensive disorders of pregnancy are associated with adverse maternal and neonatal outcome. The risk of recurrence influences parents' choices on subsequent pregnancies and the counseling obstetrician, but evidence so far has been limited. We performed the first systematic review on the risk of recurrence of hypertensive disorders that had caused delivery <34 weeks. We searched Medline, Embase, and the Cochrane Library for articles published until September 2009 that report on pregnancy outcome after an earlier pregnancy complicated by early hypertension, preeclampsia, or hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome, which resulted in a delivery before 34 weeks. Recurrence rates of premature deliveries due to hypertensive disorders were calculated for each study separately. Pooled data were calculated. The search retrieved 36 relevant articles, of which 11 fulfilled the inclusion criteria. These 11 studies reported on 2377 patients (range 18 to 1754 patients per study), who had 2461 deliveries. Seven studies were included for further calculation. The pooled risk of a delivery before 34 weeks due to recurrence of hypertension, preeclampsia, or HELLP was 7.8% (95% confidence interval 6.7 to 9.0%). Opposed to some previous studies, the overall recurrence rate is generally low. The pooled recurrence risk of an early onset hypertensive disorder is approximately 8%.