Physiologic proteinuria in labor and postpartum: The results of the postpartum proteinuria trial (PoPPy)

The urine protein to creatinine ratio (PC) is a sensitive and specific means of diagnosing preeclampsia in the antepartum period, but the 0.3 g protein per gram of creatinine threshold may be non-specific postpartum due to physiologic proteinuria after delivery. The objective of this study was to examine the reliability of PC in labor and postpartum and to determine if PC is affected by mode of delivery. This is the first study of its kind to examine physiologic proteinuria by catheterized PC in individual patients before and after delivery. This single-center prospective cohort study included two groups: term uncomplicated nulliparous patients in labor with epidural analgesia and patients for scheduled repeat cesarean deliveries. Patients with hypertension, antepartum proteinuria, renal disease, gross hematuria, or evidence of infection were excluded. Catheterized pre- and post-delivery urine PC were compared using paired t-tests. 27 and 40 patients were included in the vaginal and cesarean delivery groups, respectively. 52% of the vaginal delivery and 58% of the cesarean delivery groups were positive for proteinuria at the 0.3 g protein per g creatinine threshold. Pre- and post-delivery specimens were significantly different in the vaginal (mean difference 0.28, p = 0.05) and cesarean (mean difference 0.25, p < 0.01) delivery groups. The conclusions reached included the finding that PC measurements are unreliable in the immediate postpartum period regardless of mode of delivery, and utilizing the 0.3 threshold to diagnose preeclampsia in close proximity to delivery would contribute to increased false positive tests.