Maternal Oxygen (O2) Supplementation During Prolonged Uterine Blood Flow (Ut BF) Reduction Does Not Prevent Fetal Growth Restriction In Sheep. 234

Abstract

We have shown that 7 days of fetal hypoxemia due to Ut BF reduction results in a 38% decrease in fetal growth rate (AJP,1996). Further, 25% of the decrease in fetal growth rate was attributed to the level of fetal hypoxemia. We hypothesized that maternal O2 supplementation during Ut BF reduction would improve fetal oxygenation and prevent fetal growth restriction. Sheep were prepared with vascular catheters, a fetal crown-rump length measuring device, a vascular occluder on the maternal terminal aorta, and a catheter in the maternal trachea. Serial studies were performed 7 days apart beginning at 120-130 days gestation. Six sheep (Occluded) underwent Ut BF reduction that was maintained for 7 days after the basal study. Five sheep (Mat O2) underwent Ut BF reduction and in addition were started on 100% O2 at 2-2.5 lpm after the basal study. Results (Mean ± SD): Ut BF decreased by 37% in Occluded sheep and by 38.5% in Mat O2 sheep after the basal study. Fetal linear growth rate decreased in the Occluded sheep from 5.9 ± 2.7 to 2.7 ± 1.7mm/d (p<0.05) after the basal study and from 5.9 ± 1.0 to 3.3 ± 1.5mm/d (p=0.1) in Mat O2 sheep.Table Conclusion: Maternal O2 supplementation reduces the degree of fetal hypoxemia, but does not completely prevent the decrease in fetal growth rate that is associated with prolonged Ut BF reduction.