the relationship between maternal smoking and the prenatal origins of allergic disease was studied in 78 mothers (in thunder bay, ontario) and their newborns with a sensitive test for interleukin-4, interferon-y, and cotinine as a biological marker to validate smoking data.the relationship between maternal smoking and the prenatal origins of allergic disease was studied in 78 unselected mothers and their corresponding newborns with a sensitive test for interleukin-4 (il-4), interferon-y (ifn-y), and cotinine as a biological marker to validate smoking data. for both maternal [f(3, 74) = 26.43, g < .0001] and cord blood cotinine [f(3, 74) = 25.2, p < .0001] significantly higher levels were observed for smokers compared to non-smokers in a dose-response pattern and a high correlation was found between maternal and cord blood cotinine serum, r = .87, g < .0001, indicating a good method to confirm the presence of maternal smoking. no association was observed between cord blood il-4 and maternal smoking, maternal serum cotinine, or cord blood cotinine, respectively. an association was observed between maternal il-4 and cord blood il-4, r = .37, g < .01, suggesting a maternal-fetal cytokine interaction. newborn birth weight significantly decreased as a function of daily maternal smoking, and maternal and cord blood cotinine, in a dose-response manner. data on maternal smoking effects on selected perinatal variables are reported. discussion of the pertinence of additional studies required to elucidate mechanisms involved in prenatal sensitization in relation to maternal smoking are discussed.