The partial association of uterine contractions with changes in electrocortical activity, breathing, and PaO2 in the fetal lamb: effects of brain stem section.

In intact fetal lambs near term there was a statistically significant relation between regular small uterine contractions and a change to high-voltage fetal electrocortical activity (excess above chance 15%) or arrest of breathing (excess 12%). Isocapnic hypoxia also arrested fetal breathing. After brain stem transection there was no relation between uterine contractions and the fetal electrocortical activity, but isocapnic hypoxia increased the rate and depth of fetal breathing. Similarly uterine contractions were to a small extent associated with the initiation of fetal breathing movements which continued for about as long as the contraction. We conclude that the occasional effects of uterine contractions are consistent with diminished fetal cranial oxygen supply.