Fetal surgery: general management and operative technique for creating anomalies in sheep.

Sheep are the best experimental animals for intrauterine surgical research because the fetal lamb is sufficiently large at approximately one-third of gestation to allow handling without prohibitive fetal loss, the lamb has a relatively brief period of gestation (145 days) which allows evaluation of results in a short time, the mother sheep is easily handled and cared for, anesthetic techniques produce smooth, easy induction and steady intraoperative management with a brief recovery period appropriate uterine relaxation is readily attained without dangerously deep anesthetic levels and the sheep is a relatively inexpensive laboratory animal both in initial cost and subsequent maintenance. All aspects of preoperative, intraoperative and postoperative management of intrauterine surgery in sheep is discussed in detail and examples of specific congenital anomalies which can be created in utero are discussed. Finally, the lamb at term may be delivered by caesarian section under control conditions and then studied for evidences of altered physiology and function resulting from the intrauterine procedures.