Relation between damage to the placenta and the fetal brain after late-gestation placental embolization and fetal growth restriction in sheep

Objective: Our aim was to determine the effects of 30 days of placental insufficiency on fetal brain development and to relate placental damage to the degree of fetal brain injury. Study Design: Umbilicoplacental embolization was induced from 110 to 140 days of gestation (term, 147 days) in 7 fetal sheep, such that fetal arterial oxygen saturation was maintained at 50% of pre–umbilicoplacental embolization values. Six control fetuses were used. At 140 days the fetal brains and placentas were subjected to structural and histochemical analysis. Results: During umbilicoplacental embolization, fetal arterial oxygen saturation, PaO2, and pH were reduced (P< .05). Thirty days of umbilicoplacental embolization caused a decrease in cross-sectional area of the placentome (P< .05), with 20% of tissue showing damage. All umbilicoplacental embolization fetuses were growth restricted and had brain damage, most prominently in the cerebral white matter. There was no relation between the extent of placental damage and the severity of fetal brain damage. Conclusions: The absence of a correlation between damage to the placenta and fetal brain is likely to be caused by variations between individuals in (1) the amount of placenta that is required to be functionally damaged to achieve the prescribed level of hypoxemia and (2) the response of the fetal brain to that level of hypoxemia. (Am J Obstet Gynecol 2000;183:1013-22.)