Midtrimester abortion. Intra-amniotic instillation of hyperosmolar urea and prostaglandin F2 alpha v dilatation and evacuation.

Although dilatation and evacuation (D&E) is currently the most common method of midtrimester abortion in the United States, the intra-amniotic instillation of hyperosmolar urea and prostaglandin F2 alpha combined (U-P) has been proposed as a safer technique. To evaluate the comparative safety of U-P and D&E, we analyzed 2,805 U-P and 9,572 D&E abortions at 13 to 24 menstrual weeks' gestation. The U-P procedure resulted in significantly more serious complications than D&E (1.03 v 0.49 per 100 abortions). After adjusting for patient age, race, parity, follow-up information, and preexisting conditions, the relative risk of serious complications associated with U-P was 1.9 (95% confidence interval, 1.2 to 3.1). This advantage for D&E stems from its applicability to the 13- to 16-week interval. Although D&E appears to be safer overall in the midtrimester, for women obtaining abortion after 16 weeks, the rates of serious complications were comparable, with a relative risk of 1.0 (95% confidence interval, 0.4 to 2.5).