We report six cases of acute carbon monoxide poisoning during pregnancy. All of the women survived with good outcomes, but three cases were associated with fetal mortality. Two fetuses were delivered stillborn within 36 hours of exposure. One fetus remained alive in utero for 20 weeks and was delivered nonviable at 33 weeks gestation with multiple morphologic anomalies. Three pregnancies were carried to term and resulted in normal neonates. Maternal blood carboxyhemoglobin levels did not correlate with the concurrent severity of symptoms in the woman. Maternal symptoms at the site of exposure seemed to predict the risk of associated morbidity to the fetus. A single maternal carboxyhemoglobin level cannot be used to estimate fetal carboxyhemoglobin if the exposure pattern is not known.