A total of 2,299 dialysis units listed by the Health Care Finance Administration were surveyed to determine the frequency and course of pregnancies in dialysis patients. The responses included 930 units caring for 6,230 females aged 14 to 44 years (1,699 receiving peritoneal dialysis and 4,531 receiving hemodialysis), Two percent of the female patients of childbearing age became pregnant over a 4-year period (2.4% of the hemodialysis patients and 1.1% of the peritoneal dialysis patients). The infant survival rate was 40.2% in the 184 pregnancies in women who conceived after starting dialysis and 73.6% in the 57 pregnancies in women who started dialysis after conception. In the subset of women in whom dialysis modality was known, infant survival was not significantly different between the hemodialysis and peritoneal dialysis patients (39.5% v 37%). There was a trend toward better infant survival in women who received dialysis greater than or equal to 20 hours per week and a weak correlation between number of hours of dialysis and gestational age (P = 0.05). Maternal complications included two maternal deaths and five intensive care unit admissions for hypertensive crisis. Seventy-nine percent of women had some degree of hypertension, and 32 had blood pressure higher than 170/110 mm Hg. Only 5.9% of women had a hematocrit greater than 30% throughout pregnancy. Twenty-six percent of women treated with erythropoietin (EPO) and 77% of women not receiving EPO required transfusions. Eleven infants had congenital anomalies and 11 had long-term medical problems. Eighty-four percent of infants born to women who conceived after starting dialysis were premature. The likelihood of a surviving infant resulting from pregnancy in dialysis patients is higher than previously observed. There is no preferred dialysis modality. There is a suggestion that increased dialysis time may improve outcome. Prematurity remains a major cause of morbidity and likely contributes to a high frequency of long-term medical problems in surviving infants. (C) 1998 by the National Kidney Foundation, Inc.