Pregnancy and progression of IgA nephropathy: results of an Italian multicenter study

BACKGROUND: Whether pregnancy impacts on the long-term outcome of immunoglobulin A (IgA) nephropathy is unknown. This study aims to compare the long-term outcome of kidney disease in women with IgA nephropathy and preserved kidney function who did and did not become pregnant. STUDY DESIGN: Multicenter longitudinal cohort study. SETTING & PARTICIPANTS: Women of childbearing age with biopsy-proven IgA nephropathy, serum creatinine level<or=1.2 mg/dL at diagnosis, and minimum follow-up of 5 years after biopsy recruited from 35 nephrology centers participating in a national collaborative study group of pregnancy and kidney disease sponsored by the Italian Society of Nephrology. PREDICTORS: Pregnancy, treated as a time-dependent variable; baseline proteinuria; hypertension; and kidney biopsy histologic characteristics. OUTCOME & MEASURES: Rate of change in estimated creatinine clearance, change in proteinuria, and new-onset hypertension. RESULTS: 245 patients were enrolled. Of these, 223 women (136 and 87 in the pregnancy and nonpregnancy groups, respectively) had serum creatinine levels<or=1.2 mg/dL at diagnosis. Baseline data (including age, estimated creatinine clearance, prevalence of hypertension, and histologic grade of kidney damage) were similar between groups with the exception of proteinuria (protein excretion, 1.33 vs 0.95 g/d in the pregnancy vs nonpregnancy groups, respectively; P=0.03). Kidney function decreased 1.31 mL/min/y (95% CI, 0.99-1.63) during a median follow-up of 10 years (range, 5-31 years) and did not differ between groups. Baseline proteinuria predicted a faster decrease, but did not modify the effect of pregnancy. Pregnancy did not affect changes in proteinuria over time or risk of new-onset hypertension. LIMITATIONS: Unrecognized or unmeasured factors associated with the decision of becoming pregnant might have influenced results. CONCLUSIONS: Pregnancy does not seem to affect the long-term outcome of kidney disease in women with IgA nephropathy and preserved kidney function.