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 ins ufficiency 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 da ys of gestation (term, 147 days) in 7 fetal sheep, such that fetal arterial oxygen saturation was maintained at 50% of pre-umbilico-placental emboliza tion values. Six control fetuses were used. At 140 days the fetal brains an d placentas were subjected to structural and histochemical analysis. RESULTS: During umbilicoplacental embolization, fetal arterial oxygen satur ation, PaO2, and pH were reduced (P < .05). Thirty days of umbilicoplacenta l embolization caused a decrease in cross-sectional area of the placentome (P < .05), with 20% of tissue showing damage, All umbilicoplacental emboliz ation 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 an d 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 ac hieve the prescribed level of hypoxemia and (2) the response of the fetal b rain to that level of hypoxemia.