PHILADELPHIAIt 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
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.