Association of Proteinuria Threshold in Pre-Eclampsia with Maternal and Perinatal Outcomes: A Nested Case Control Cohort of High Risk Women

OBJECTIVES: To evaluate occurrence of adverse maternal and perinatal outcomes with different thresholds of proteinuria (300-499 mg and ≥500 mg/24 hours) in pre-eclamptic women, comparing outcomes against women with chronic and gestational hypertension. DESIGN: Secondary analysis of the Vitamins in Pre-Eclampsia Trial. SETTING: 25 UK hospitals in ten geographical areas. POPULATION: 946 women with pre-existing risk factors for pre-eclampsia. METHODS: Women with pre-eclampsia and proteinuria 300-499 mg/24 h (PE300, referent group, n=60) or proteinuria ≥500 mg/24 h (PE500, n=161) were compared with two groups of non-proteinuric women with chronic hypertension (CHT, n=615) or gestational hypertension (GH, n=110). MAIN OUTCOME MEASURES: MATERNAL: progression to severe hypertension. Perinatal: small for gestational age (SGA) <5(th) centile, gestation at delivery. RESULTS: Severe hypertension occurred more frequently in PE500 (35%) and PE300 (27%) than CHT (5.9%; P≤0.01) and GH (10%; p≤0.001). Gestation at delivery was earlier in PE500 (33.2 w) than PE300 (37.3 w; P≤0.001), and later in CHT (38.3 w; P≤0.05) and GH (39.1 w; P≤0.001). SGA infants were more frequent in PE300 (32%) than in CHT (13.3%; P≤0.001) and GH (16.5%; P≤0.05). Women in PE500 were more likely to have a caesarean section than PE300 (78% vs. 48%; P≤0.001), and to receive magnesium sulphate (17% vs. 1.7%, P≤0.05). CONCLUSION: Women with PE300 have complication rates above those of women managed as out-patients (GH and CHT), meriting closer surveillance and confirming 300 mg/d as an appropriate threshold for determining in-patient management. Adverse perinatal outcomes are higher still in women with PE500.