The clinical course and pregnancy outcome of all patients undergoing extensive nonobstetric operation during pregnancy during a ten-year period was reviewed. During this time, there were 49,567 births and 78 women had nonobstetric operation; an incidence of one in 635. The most common indications for surgical treatment were appendicitis, adnexal mass and cholecystitis. The perinatal mortality rate was not increased in women undergoing nonobstetric operation, provided that fetal viability was established preoperatively. In this series, there was no measurable benefit from the use of perioperative prophylactic tocolytic agents. However, nonobstetric operation was associated with an increased risk of preterm labor. Postoperatively, patients should be monitored for contractions and treated with tocolytic agents when appropriate.