All infants born in 1973-1978 to nurses working in anesthesiology or as operating room nurses were identified from a nationwide registry of all births in Sweden, a registry of hospitalized spontaneous and legally induced abortions that covers 70% of Sweden, and a nurse registry (n = 1323). For comparison, a group was formed that consisted of nurses working in medical wards (n = 1382). Delivery outcome was also compared with the estimate expected from nationwide figures. No statistically significant differences were seen, but infants of the anesthesiology/operating room nurses had a slightly higher perinatal death rate and a slightly higher rate of preterm births and low birth weights than infants in the comparison group and the nationwide average. On the other hand, the malformation rate was lower in the infants of anesthesiology/operating room nurses than in the control group or nationwide average. A case-control study within the group of anesthesiology/operating room nurses was performed. Questionnaires were sent to 75 nurses (25 cases whose infants died or had serious malformations; 50 controls whose infants were normal); 74 responded. The only difference in working conditions for cases and controls was that the cases had worked after the twenty-eighth week of pregnancy more often than the controls. However, this finding was restricted to nurses whose infants were malformed, and work after the twenty-eighth week cannot affect malformation rate. Work in anesthesiology or operating rooms had no effect on the incidence of hospitalization for miscarriage, perinatal deaths, or malformations detected in the neonatal period.