The impact of pre-eclampsia definitions on the identification of adverse outcome risk in hypertensive pregnancy - analyses from the CHIPS trial (Control of Hypertension in Pregnancy Study).

OBJECTIVE To examine the relationship between pre-eclampsia definition and pregnancy outcome. DESIGN Secondary analysis of CHIPS trial data. SETTING International multi-centre RCT. POPULATION 987 women with non-severe non-proteinuric pregnancy hypertension. METHODS We evaluated the relationship between pre-eclampsia definitions and adverse pregnancy outcomes, stratified by hypertension type and blood pressure control. MAIN OUTCOME MEASURES Main CHIPS trial outcomes: primary (perinatal loss or high-level neonatal care for >48hr), secondary (serious maternal complications), birth weight <10th centile, severe maternal hypertension, delivery at <34 or <37 weeks, and maternal hospitalisation before birth. RESULTS Of 979/987 women with informative data, 280 (28.6%) progressed to pre-eclampsia defined restrictively by new proteinuria, and 471 (48.1%) to pre-eclampsia defined broadly as proteinuria or one/more maternal symptoms, signs, or abnormal laboratory tests. The broad (vs. restrictive) definition had significantly higher sensitivities (range 62-79% vs. 36-50%), lower specificities (range 53-65% vs. 72-82%), and similar or higher DOR and 'true' to 'false' positives ratios. Stratified analyses showed similar results. Addition of available fetoplacental manifestations (stillbirth or birthweight <10th centile) to the broad pre-eclampsia definition improved sensitivity (74-87%). CONCLUSIONS A broad (vs. restrictive) pre-eclampsia definition better identifies women who develop adverse pregnancy outcomes. These findings should be replicated in a prospective study within routine health care to ensure that the anticipated increase in surveillance and intervention in a larger number of women with pre-eclampsia is associated with improved outcomes, reasonable costs, and congruence with women's values.