Elevated frequencies of hprt mutant lymphocytes in cigarette-smoking mothers and their newborns

Maternal cigarette smoking during pregnancy has been associated with increased perinatal mortality and low birth weight. Several epidemiological studies have demonstrated an association between smoking during pregnancy and an elevated risk of hematopoietic cancer in the child, but other studies have failed to confirm this association. We have used an assay for somatic cell mutation to evaluate the in utero effects of exposure to maternal cigarette smoking. Cord blood samples were obtained from 10 newborns whose mothers smoked cigarettes during pregnancy and 10 newborns of non-smoking mothers. Blood samples were also obtained from 5 of the smoking and 5 of the non-smoking mothers. Smoking status was confirmed in all samples by testing the blood plasma for cotinine. The frequency of lymphocytes containing mutations at the hypoxanthine phosphoribosyltransferase (hprt) locus was determined with an autoradiographic assay using cells that had been cryopreserved. The mothers who were smokers had a mean frequency (±SE) of 3.08 (±0.55) variant (mutant) cells per 10⁶ evaluatable lymphocytes. The frequency (Vf) in non-smokers was 1.07 (±0.17) × 10^-6. The Vf of newborns of smokers was 2.17 ±0.24 × 10^-6, and new borns of non-smokers had a Vfof 0.77 (±0.13) × 10^-6. In both mothers and newborns the difference in Vf between smokers and non-smokers was statistically significant (p < 0.05). Maternal and newborn Vfs were significantly correlated (r = 0.88; p < 0.004), and there was a positive association (r = 0.86; p < 0.001) between the reported number of cigarettes smoked per day and the Vfs. This study provides further evidence that maternal smoking may be hazardous to the future health of children exposed in utero to mutagenic agents in cigarette smoke.