Maternal smoking causes fetal hypoxia: experimental evidence.

Cigarette smoking during pregnancy has been related to poor perinatal outcome. To investigate the changes in maternal and fetal arterial blood gases associated with smoking, five chronically catheterized pregnant rhesus monkeys were exposed to standard cigarette smoking (N = 5) and nicotine-free herbal cigarette smoke (N = 3). The only consistently reproducible and significant finding was a drop in fetal PO2. The timing of the decline in PO2 and the similar responses to standard and nicotine-free cigarette smoke make carboxyhemoglobin the most likely causative factor.