Obstetrical outcomes of women with new-onset isolated proteinuria diagnosed after 24 weeks' gestation.

Purpose: To assess a possible association between marked proteinuria and the risk of preeclampsia with severe features, as defined by the American College of Obstetricians and Gynecologists.

Methods: This retrospective study included data recorded at a tertiary university-affiliated hospital between 2017 and 2022. Women at or beyond 24 weeks of gestation with proteinuria (protein levels > 300 mg in a 24 h urine collection) and normal blood pressure during the initial 48 h of admission were included. Obstetrical and neonatal outcomes were compared between women with mild proteinuria (300-1000 mg/24 h) and marked proteinuria (≥ 1000 mg/24 h).

Results: Among the women with marked proteinuria (n = 48) compared to those with mild proteinuria (n = 108), the incidences were higher of preeclampsia (50.0% vs. 22.2%, p = 0.001) and of preeclampsia with severe features (18.8% vs. 2.8%, p < 0.001). In multivariate analysis that adjusted for maternal age, primiparity, multiple pregnancy, uric acid level > 6 mg/dL and aspirin treatment, marked proteinuria was a risk factor for preeclampsia with severe features (adjusted odds ratio [aOR] = 10.2, confidence interval [CI] 95% 1.9-54.0, p = 0.007) and for small-for-gestational-age infants (aOR = 2.4, 95% CI 1.02-5.6, p = 0.001). Among women with marked compared to mild proteinuria, rates were also higher of labor induction (58.3% vs. 25.9%, p < 0.001), indicated preterm delivery (41.7% vs. 25.0%, p = 0.04) and admission to the neonatal intensive care unit (44.1% vs. 25.8%, p = 0.017).

Conclusions: Women with marked compared to mild isolated proteinuria showed higher risk of developing preeclampsia with severe features and of delivering small-for-gestational-age neonates.