Fetal surgery in the primate I. Anesthetic, surgical, and tocolytic management to maximize fetal-neonatal survival.

There are compelling physiologic arguments for correcting certain malformations before birth. Although fetal surgery has been successful in sheep and lower animals, it has proven difficult in primates because the gravid uterus is exquisitely sensitive to induction of preterm labor and abortion. Because the feasibility of fetal intervention can be determined only in a primate model, we have investigated the variables affecting fetal-neonatal survival after fetal surgery in 25 monkeys. As we improved our anesthetic and surgical techniques and refined our tocolytic therapy, mortality fell from 73.3% (11/15) to 20% (2/10). Since spontaneous perinatal loss in 56 controls was 21.4% we can now operate on the late second and early third trimester fetal monkey without increasing maternal or fetal-neonatal mortality. Success in this rigorous model is a requisite for attempted correction of human malformations in utero.