3 Is BP level achieved related to maternal and perinatal outcomes? A secondary analysis of bp values from the chips (control of hypertension in pregnancy study) randomised controlled trial

Abstract

Background Blood pressure (BP) level and variability have been associated with adverse cardiovascular outcomes, particularly for younger age groups, and the outcome of stroke. We examined the relationship between pregnancy outcomes and both BP level and variability among participants in the CHIPS Trial (Control of Hypertension In Pregnancy Study, NCT01192412). Methods BP level was defined as mean systolic (sBP) and diastolic (dBP) between randomisation and delivery. Our primary definition of BP variability was the SD of the two highest and two lowest post-randomisation office visit BP values (a better estimate of relevant variability because numerous measurement at a stable BP would give an underestimate of the type of variability with which we are concerned), and measured at least a week apart because measures taken close together tend to be both highly correlated and more frequently recorded when BP is unstable or ‘spiking'. Relationships were explored between outcomes and each of BP level and variability for the major outcomes in CHIPS: perinatal loss or high level neonatal care for >48h (primary outcome), birth weight P Results Of the 987 women in CHIPS, 961 had at least one office visit (median 7, IQR 4, 10). For each of ‘less tight' (vs. ‘tight') control, BP was higher among women who had an adverse outcome (vs. women who did not) for all but serious maternal complications of which there were few [ N =28]: primary outcome [ p p =0.04 for sBP and p p =0.27 for sBP and p =0.002 for dBP); severe hypertension and pre-eclampsia ( p Conclusions Higher BP is a biomarker for adverse outcomes, even when target BP is low as in‘tight' control. Although CHIPS showed that BP-lowering with antihypertensive therapy can reduce maternal risk (i.e., less severe hypertension), CHIPS did not show that perinatal risk is lowered (or increased). BP variability has a significant complex relationship with outcomes, possibly related to an adaptive response from the feto-placental unit. Our data suggest that when antihypertensive therapy is not achieving target BP values or BP is not stable, enhanced surveillance may be prudent.