OBJECTIVE: The objective of the study was to determine the value of maternal serum Down syndrome screening in patients affected by renal disease. STUDY DESIGN: A study group of 54 pregnant women with renal diseases defined before pregnancy, was compared with a control group of 108 patients matched for maternal age, maternal weight, smoking status, and gestational age. Maternal serum markers (free beta-human chorionic gonadotropin [hCG], total hCG, alpha-fetoprotein) expressed in multiple of median and maternal renal function markers (creatinine, beta2-microglobulin, alpha1-microglobulin) were assayed. RESULTS: The percentage of patients in the Down syndrome at-risk group (>1:250) using free beta-hCG was significantly higher (P < .02) in the renal disease group (48%) than in the control group (12%). No significant difference was observed for total hCG (25% vs 15%). CONCLUSION: Down syndrome screening using free beta-hCG is not applicable in patients with renal disease whatever the maternal serum creatinine and can be used with caution when total hCG is used.