The Control of Hypertension In Pregnancy Study (CHIPS) randomized controlled trial – is severe hypertension just an elevated blood pressure?

To determine whether clinical outcomes differed by occurrence of severe hypertension in the international CHIPS Trial (ISRCTN 71416914), adjusting for the interventions of ‘less tight’ [target diastolic blood pressure (dBP) 100mmHg] vs. ‘tight’ control [target dBP 85mmHg]. In this post-hoc analysis of CHIPS data from 987 women with non-severe non-proteinuric pre-existing or gestational hypertension, mixed effects logistic regression was used to compare the following outcomes according to occurrence of severe hypertension, adjusting for allocated group and the influence of baseline factors: CHIPS primary (perinatal loss or high level neonatal care for >48hr) and secondary outcomes (serious maternal complications), birth weight <10th centile, pre-eclampsia, delivery at <34 or <37 weeks, platelets <100x109/L, elevated liver enzymes with symptoms, maternal length of stay ≥10 days, and maternal re-admission before 6 weeks postpartum. 334 (34.1%) women in CHIPS developed severe hypertension that was associated with all outcomes examined except for maternal re-admission (p=0.20): CHIPS primary outcome, birth weight <10th centile, pre-eclampsia, preterm delivery, and elevated liver enzymes (all p<0.001), platelets <100x109/L (p=0.006), and prolonged hospital stay (p=0.03). The association between severe hypertension and serious maternal complications was seen only in ‘less tight’ control (p=0.02). Adjustment for pre-eclampsia (464, 47.3%) did not negate the relationship between severe hypertension and the CHIPS primary outcome (p<0.001), birth weight <10th centile (p=0.005), delivery at <37 (p<0.001) or <34 weeks (p<0.001), or elevated liver enzymes with symptoms (p=0.02). Severe hypertension is a risk marker for adverse maternal and perinatal outcomes, independent of BP control or pre-eclampsia co-occurrence.