Video-endoscopic technology may offer new hope for the future of fetal surgery. Ten time-dated pregnant ewes (95 to 105 days; term, 145 days) were used to develop a model of fetal surgery through intrauterine endoscopy. Special 5-mm ports were designed with short, flexible, balloon-tipped shafts. The cannulas were inserted through purse-stringed hysterostomies. Amnioinfusion of warmed physiological fluid (Hartmann) was used as the work medium. Fetal heart rate and oxygen saturation (pulse oximetry), temperature, and amniotic pressure were monitored continuously through endoscopically placed sensors. Surgical procedures included subcutaneous dissection of the abdominal wall and ligation of the urethra in the male fetus (n = 7), ligation of the urachus within the umbilical cord (n = 8), and endoscopy of the fetal esophagus and trachea (n = 6). Bloodless surgery was achieved with a novel coagulation device that allows bipolar cutting and coagulation in an electrolyte-rich fluid medium. The mean fetal operative time was 147 minutes (range, 130 to 195). The intraamniotic temperature was maintained between 38.0 +/- 0.9 degrees C and 41.7 +/- 1.7 degrees C throughout the procedure. Oxygen saturation ranged from 51 +/- 20% to 72 +/- 14%, and fetal heart rate from 120 to 140 beats per minute. In conclusion, intrauterine endoscopy in a fluid medium allows fully monitored surgical procedures, lasting more than 2 hours, to be performed on the fetal lamb.