One of the major effects of cigarette smoking during pregnancy is bearing a child with lower
birth weight. It has previously been demonstrated under experimental conditions in rats that exposure to reference cigarette
smoke results in reduced
birth weight (E. L. Carmines et al., 2003, Toxicol. Sci. 75, 134-147; C. L. Gaworski et al., 2004, Toxicol. Sci. 79, 157-169). The role of various
smoke constituents on lower
birth weight was evaluated by exposing time-pregnant Sprague-Dawley rats at the concentrations found in cigarette
smoke. The rats were exposed for 2 h/day 7 days/week by nose-only inhalation. The target concentrations were designed to produce the same plasma levels of
biomarkers as exposure to 2R4F reference cigarette
smoke at a concentration of 600 mg/m(3) total
particulate matter. The
smoke constituents evaluated included
carbon monoxide (CO),
nicotine, and a mixture of
aldehydes (
acrolein,
acetaldehyde, and
formaldehyde). The
smoke constituents were tested individually as well as in mixtures to evaluate potential interactions. Exposure to cigarette
smoke during gestation produced a reduction in both maternal
body weight gain and
fetal weights. Exposure to
nicotine reduced maternal
body weight gain but had no effect on
fetal weight. Exposure to CO had no effect on maternal
body weight gain but reduced
fetal weight to a degree comparable to cigarette
smoke. Exposure to a mixture of
aldehydes (
acrolein,
acetaldehyde, and
formaldehyde) had no effect on either maternal
body weight gain or
fetal weight. Exposure to mixtures of
nicotine and CO or
nicotine, CO, and
aldehydes did not demonstrate any interactions. The results of this study suggest that the observed reduction in
fetal weight after exposure to cigarette
smoke in rats is due to CO toxicity and not
nicotine toxicity.