Effects of reduction of placental size in sheep

The number of uterine caruncles was reduced by electrocautery in nonpregnancy sheep. Subsequent pregnancies were studied as chronic fetal sheep preparations between 110 days' gestation and term; findings were compared with those for control chronic fetal sheep preparations at a similar gestational age. As a result of decreased weight and reduced number of cotyledons, the placenta in experimental animals was significantly smaller compared with that in controls. The weights of the fetal liver and heart were decreased, fetal PO2 was decreased, and fetal PCO2 and hematocrit levels were increased in the experimental group. Fetal plasma fructose levels were decreased in experimental animals, but fetal blood lactate, pyruvate, and plasma glucose levels were similar in both groups. No differences were demonstrated in fetal plasma or amniotic fluid cortisol levels and amniotic fluid lecithin : sphingomyelin ratios. Fetal respiratory-like activity was significantly depressed in the experimental group.