First-trimester urinary protein levels and adverse pregnancy outcomes in low-risk women: implications for reassessing...

To evaluate the association between first-trimester 24-h urinary protein levels (50-300 mg) and maternal/perinatal outcomes in low-risk pregnancies, focusing on subthreshold proteinuria (150-300 mg/24 h).

A retrospective cohort study analyzed 237 low-risk pregnant women with singleton gestations and first-trimester urinary protein levels of 50-300 mg/24 h at Ruijin Hospital (2015-2020). Participants were stratified into two groups: 50-150 mg/24 h (n = 158) and 150-300 mg/24 h (n = 79).

Women with 150-300 mg/24 h proteinuria exhibited significantly higher systolic blood pressure (123.1 vs. 119.1 mmHg, p < 0.05) and mean arterial pressure (92.3 vs. 89.7 mmHg, p < 0.05). Women with urinary protein 150 ∼ 300mg/24 h were more likely to develop gestational hypertension (11.4% compared with 4.4%), preeclampsia (6.3% compared with 0), compared with women with urinary protein 50 mg-150 mg/24 h. The proportions of FGR, preterm, low birth weight infants were increased in the group with urinary protein 150 ∼ 300mg/24 h compared with the group with urine protein 50 ∼ 150mg/24h (6.3% VS 0.63%, 20.3% VS 8.2%, 12.7% VS 3.2%, p < 0.05).

Even within the conventional 'normal' range (<300 mg/24 h), first-trimester urinary protein levels of 150-300 mg/24 h are associated with increased risks of hypertensive disorders and adverse perinatal outcomes.