The effects of glycemia on breathing movements and plasma prostaglandin E concentrations in the sheep fetus.

Abstract

The purpose of this study was to determine the roles of fetal plasma glucose and prostaglandin E in controlling fetal breathing movements. Five late pregnant ewes with catheterized twin fetuses were fasted for 48 hours; one fetus was kept normoglycemic (by glucose infusion) and the other allowed to become hypoglycemic during this period. Fetal breathing movement and fetal and maternal plasma prostaglandin E and glucose concentrations were measured throughout. Data were analyzed by paired and unpaired t tests. The mean incidence of fetal breathing movement was significantly greater in the normoglycemic fetuses that in the hypoglycemic twins at the end of the fast (p less than 0.05), whereas plasma prostaglandin E levels increased significantly (p less than 0.05) and to the same extent in both groups of fetuses. The reduced incidence of ovine fetal breathing movement that occurs during maternal fasting appears to be primarily caused by fetal hypoglycemia and does not directly involve changes in fetal plasma prostaglandin E.