Kidney Biopsy During and After Pregnancy: Clinical Characteristics, Pathologic Findings, and Complications

Background: Pregnancy induces significant physiologic changes in renal function that may unmask undiagnosed kidney disease or worsen preexisting conditions. Characterizing renal pathology in pregnancy and postpartum is critical for guiding diagnosis, management, and improving maternal-fetal outcomes. We evaluated patients with significant kidney disease during pregnancy or postpartum (PP) requiring a kidney biopsy. Methods: We conducted a retrospective study of adults who underwent native kidney biopsy during pregnancy or within 12 weeks PP at a single center (2006-2024). Demographic, clinical, and laboratory data were extracted from electronic medical records, along with pathology reports and biopsy-related complications. Descriptive statistics were used to compare clinical characteristics and biopsy findings between groups. Results: Overall, 45 women underwent kidney biopsy- 23 during pregnancy and 22 PP (Table 1). Indications were proteinuria (80%) or elevated creatinine (40%). Patients biopsied during pregnancy were younger (29 ± 6.0 yrs vs 33 ± 7 yrs). Black women made up 56% of the cohort. Pre-existing conditions included hypertension (47%), CKD (42%), and lupus nephritis (36%). Those biopsied during pregnancy had lower mean eGFR and proteinuria was similar across groups. Pre-eclampsia was seen in 49%. Common diagnoses were de-novo or chronic lupus nephritis in 15 (33%), secondary focal segmental glomerulosclerosis in 9(20%), de-novo glomerular disease (IgA nephropathy, thin basement, membranous, Alport, thrombotic microangiopathy etc.) in 15 (33%). The rest had acute tubular injury or preeclampsia. Interstitial fibrosis and tubular atrophy was mild in 42%, moderate in 18%, and severe in 16%. Biopsy [complications were rare: 2(4%) had hematoma and 3(7%) transient hematuria. Conclusion: In this cohort, kidney biopsy during pregnancy and postpartum provided actionable diagnostic information with a low complication rate. Histopathologic findings were diverse but similar across groups, offering insight into peripartum kidney disease.