Perinatal exposure to nicotine is associated with fetal abnormal development,including brain damage.This study determined the effect of administration of nicotine hydrogen tartrate (3mg/kg/day) in maternal rats,from early,middle,and late gestation,on fetal blood hemoglobin associated with in utero hypoxia,and expression of cholinergic receptor subtypes in the fetal brain.The results showed that subcutaneous nicotine from the early gestation in maternal rats could increase fetal blood hemoglobin and hematocrit associated with reduction of PO2.Nicotine used during late gestation had no effects on fetal brain weight.