Association of Baseline Proteinuria and Adverse Outcomes in Pregnant Women with Treated Chronic Hypertension

OBJECTIVE: To assess the importance of baseline proteinuria in women treated for chronic hypertension during pregnancy. METHODS: This retrospective cohort study included women with chronic hypertension who received antihypertensive therapy in the first half of pregnancy and completed urine protein quantification before 20 weeks of gestation. Maternal and neonatal outcomes were analyzed according to the presence or absence of baseline proteinuria, defined as 300 mg or greater per 24 hours identified before 20 weeks of gestation. Frequencies of superimposed preeclampsia, preterm birth, and small-for-gestational-age neonates were further evaluated according to stratified urine protein excretion levels from less than 50 mg to greater than 1,000 mg/24 hours. RESULTS: Between January 2002 and December 2014, a total of 447 women met inclusion criteria. Of these, 56 (13%) had baseline proteinuria. Women with baseline proteinuria were statistically significantly more likely to develop superimposed preeclampsia (79% compared with 49%), deliver preterm (18% compared with 6% 30 weeks of gestation or less, 34% compared with 17% 34 weeks of gestation or less, and 48% compared with 26% less than 37 weeks of gestation), and deliver an small-for-gestational-age neonate (41% compared with 22% less than the 10th percentile, 20% compared with 9% less than the third percentile) when compared with women who did not have proteinuria (all P<.05). Furthermore, the rates of superimposed preeclampsia and small for gestational age were significantly increased as 24-hour protein excretion levels increased across stratified levels (P for trend.002 and.015, respectively). When proteinuria levels less than 300 mg/d were analyzed separately, a significant association was observed for rates of superimposed preeclampsia and preterm birth. CONCLUSION: In pregnant women with treated chronic hypertension, baseline proteinuria was significantly associated with increased rates of preeclampsia, preterm birth, and growth restriction - even at proteinuria values previously considered to be within normal range (less than 300 mg/d).