General anesthesia for intrauterine placement of human conceptuses after in vitro fertilization.

General anesthesia has been used for the replacement of human conceptuses after in vitro fertilization (IVF). Two adjuvants, enflurane and halothane, have been compared. Halothane significantly reduced the incidence of implantation compared to enflurane. In 356 replacements, the incidence of implantation for enflurane and halothane was 34 and 17%, respectively (P = 0.005). Sixty-four percent of all replacements had three conceptuses; the incidence of implantation for enflurane and halothane in this group was 43 and 19%, respectively (P = 0.002). The incidence of multiple pregnancy was similar for both anesthetic agents (20%) and the demise of implantation sacs 5 weeks postovulation was 11% for enflurane and 12% for halothane.