THE EFFECT OF OPEN AND ENDOSCOPIC FETAL SURGERY ON UTEROPLACENTAL OXYGEN DELIVERY IN THE SHEEP

Open fetal surgery predictably results in postoperative uterine contra ctions and often in premature labor, but its intraoperative effects on the uterus are not known. In 10 pregnant ewes (108 to 115 days' gesta tion), uterine artery flow, uterine venous oxygen saturation, arterial saturation, and uterine electromyography were recorded simultaneously (control). Six ewes underwent a stapled hysterotomy, and four underwe nt placement of three endoscopic surgery cannulas and amnioinfusion. U terine contractions were present 52% of the time (range, 34% to 72%), and there was no significant difference between control, hysterotomy, and endoscopic access. Uterine artery blood flow and uteroplacental ox ygen delivery at rest decreased (to 73% of control) after hysterotomy (P < .05), but not after endoscopy. Fetal + uteroplacental oxygen cons umption did not differ significantly between the groups. In conclusion , (1) uteroplacental oxygen delivery after hysterotomy alone decreased to levels critical for adequate fetal oxygenation; (2) endoscopy did not alter uteroplacental oxygen delivery; and (3) during open fetal su rgery, further oxygen demand/delivery mismatch is likely, by traction on uterine and umbilical vessels and fetal stress. Copyright (C) 1996 by W.B. Saunders Company