Kidney biopsy during pregnancy: indications, complications, results, and therapeutic impact

BACKGROUND AND HYPOTHESIS: The diagnosis of kidney disease can be challenging during pregnancy. A kidney biopsy (KB) may be proposed, but there is little recent data available to assess the risk/benefit ratio of this procedure during pregnancy. METHODS: In this French nationwide survey, we analysed the indications, complications, histological diagnoses, treatments, and obstetric outcomes of pregnant women who underwent native KB between 2006 and 2025. RESULTS: We gathered the medical records of 76 patients, with a median age of 29.5 [range 18-42] years, including 2 with twin pregnancies. KB was performed at a median gestational age of 13.5 [range 4-26] weeks. The main indications for KB were: nephrotic syndrome without AKI (40.8%) and non-nephrotic proteinuria without AKI (40.8%). KB led to a diagnosis in 72 (94.7%) patients. The main histological diagnoses were lupus nephritis (43%), focal segmental glomerulosclerosis (13%), membranous nephropathy (13%), IgA nephropathy (12%), and idiopathic nephrotic syndrome consistent with minimal change disease (5%). One patient experienced bleeding requiring transfusion. Specific treatment was initiated in 48 (63.2%) patients after KB: corticosteroids (35.5%), hydroxychloroquine (27.6%), azathioprine (18.4%), calcineurin inhibitor (13.2%), rituximab (2.6%) and belimumab (1.3%). There was a high incidence of preeclampsia (16.4%), small for gestational age (21.3%) and intrauterine fetal death (9.0%) in this cohort. Preterm birth and low birth weight occurred in 65.0% and 56.7% of cases, respectively. CONCLUSIONS: When considered necessary to establish a diagnosis during pregnancy, kidney biopsy performed in the first two trimesters appears to be safe, with a high diagnostic yield and a significant impact on therapeutic decision-making and patient management.