Fetus May Be Harmed by Second-Hand Smoke

PHILADELPHIA—It has been shown that the fetus may be damaged by maternal smoking. Now, new research finds that even maternal exposure to second-hand smoke may harm the fetus. The findings were presented in two studies at the annual meeting of the American Association for Cancer Research.

“The results of our study indicate that exposure of expectant mothers to second-hand smoke is a major cause of concern because the unborn baby is also exposed to cancer-causing chemicals,” said Steven R. Myers, PhD, associate professor of pharmacology and toxicology, and co-director, Center for Environmental Science, University of Louisville School of Medicine. Dr. Myers conducted the research along with Dr. M.P. Ross of the Department of Pediatrics.

“In this study, we examined the effect of passive exposure to tobacco smoke and the subsequent formation of both maternal and fetal 4ABP hemoglobin (Hb) adducts,” he said. The carcinogens assessed included 4-aminobiphenyl (4ABP), benzo(a)pyrene, and the tobacco-specific nitrosamines NNN and NNK.

The researchers studied three groups of mothers: those who smoked one to two packs a day (smokers), those who did not smoke but were exposed to smoke at least 8 hours a day at work or at home (passive smokers), and nonsmokers.

Upon admission of the woman for labor and delivery, maternal urine was obtained for coti-nine assessment and maternal blood for Hb adduct determinations. Fetal blood was obtained via the umbilical vein for assessment of fetal exposures to tobacco smoke carcinogens.

The results showed that women exposed to passive smoke during pregnancy had significantly elevated levels of 4ABP (maternal, 104.3 pg/g Hb; fetal, 46.2 pg/g Hb) adducted to both maternal and fetal hemoglobin, compared with nonsmokers (maternal, 34.6; fetal, 12.4). However, Dr. Myers reported, these values were significantly lower than the maternal and fetal values of 4ABP adducts obtained in smokers (375.2 and 162.9, respectively).

Further Investigation Warranted

“These results demonstrate that exposure to passive cigarette smoke is a concern during pregnancy,” he concluded, “and the levels of Hb adduct detected as a result of passive smoke exposure warrant further investigations as to the health effects of in utero exposure to passive smoke.”

In another study on the effects of second-hand smoke on the fetus, Ed Nelson, MedB, ScD, professor of toxicology, Essen University School of Medicine, Germany, exposed a group of pregnant rats to second-hand smoke. After the rat pups were born, their lungs were examined for any pathologic changes.

Several changes were found in the lungs of these newborn rats that are similar to those that precede lung cancer. “In contrast, rats born to mothers with no smoke exposure failed to show any of these changes,” Dr. Nelson said. Not only were precancerous lesions found in the lungs of the newborn rats exposed to tobacco smoke, he said, “but other tissues like kidney, liver, and stomach also showed pathologic abnormalities, although these were not graded as preneoplastic.”

He concluded that passive smoking during pregnancy not only causes fetal growth retardation but might also cause preneoplastic damages in the lung tissue. Dr. Nelson recommended that physicians strongly advise women to avoid tocacco smoke exposure for any duration at any period during a pregnancy.