There are several published series of pregnancy in patients with nonimmunoglobulin A mesangial proliferative glomerulonephritis (most of whom have thin basement membrane nephropathy [TBMN]). The aim of the present study was to review the maternal and fetal outcomes of pregnancy in women with TBMN. The medical and obstetric histories of 86 women with TBMN and their 182 pregnancies (one twin) were reviewed. Data were collected retrospectively in 164 pregnancies (90%) and prospectively in 18 pregnancies (10%). Hypertension (alone or with proteinuria) developed in 15 unmonitored pregnancies (9%), and proteinuria alone developed in the third trimester in 2 pregnancies (1%). Hypertension was more common in the prospectively monitored pregnancies (6 pregnancies, 33%). In all, there were 174 live births (95%), and all fetal deaths occurred in the first and second trimesters in the absence of maternal complications. However, all the mothers of the 4 small for gestational age babies had been hypertensive. In TBMN, maternal hypertension, prematurity, and small for gestational age rates did not exceed those in the normal population. Overall, pregnancy in women with TBMN does not appear to be attended by a significantly increased maternal or fetal risk.