The study on the hazard of passive smoking to the fetus during pregnancy was carried out in 188 cases. The rate of SGA, premature labor and neonatal asphyxia in this group were higher than that of 65 cases without passive smoking. The data was analysed by logistic multifactor regression analysis. The result showed that, for those patients with hypertension and husband smoking, the risk of SGA, and neonatal asphyxia were 1.6, 2.8 and 3.2 times higher than those without hypertension and husband smoking. In the group of passive smoking, their blood CoHb and umbilical venous CoHb levels were obviously higher than those of the normal control. The possible cause of hazard of passive smoking to the fetus was also analysed and discussed.