Maternal Cigarette Smoking During Pregnancy

Maternal Cigarette Smoking During Pregnancy

Introduction: The relationship between maternal cigarette smoking during pregnancy and reduced birth weight or increased risk of low birth weight (LBW) may be modified by maternal genetic susceptibility. The association between maternal cigarette smoking and infant birth weight was examined to determine whether birth weight varies by polymorphisms of 2 maternal metabolic genes: CYP1A1 AND GSTT1.

Methods: Between 1998 and 2000, a molecular epidemiologic investigation was conducted by using a case-control design in 741 mothers (174 ever smokers and 567 never smoker) who delivered sigleton live infants. Of these, 207 were preterm or LBW infants and 534 were non-LBW, full-term infants (controls). The primary outcome measures were birth weight, gestation, fetal growth by smoking status and CYP1A1 Mspl (AA vs Aa and aa, where Aa and aa were combined because of small numbers of aa and similar results), and GSTT1 (present vs absent) genotypes.

Results: Without considering genotype, continuous maternal smoking during pregnancy was correlated with a mean reduction of 377 g in birth weight (odds ratio [OR], 2.1; 95% CI, 1.2-3.7). When CYP1A1 genotype was considered, the estimated decrease in birth weight was 252 g for AA genotype group (75 infants; OR, 1.3; CI, 0.6-2.6); it was 520 g for the Aa/aa genotype group (43 infants for Aa and 6 for aa; OR, 3.2; 95% CI, 1.6-6.4). When the GSTT1 genotype was considered, the estimated decrease in birth weight was 285 g (OR, 1.7; 95% CI, 0.9-3.2) and 642 g (OR, 3.5; 95% CI, 1.5-8.3) for the present and absent genotype groups, respectively. When both CYP1A1 and GSTT1 genotypes were considered, the greatest decrease in birth weight was observed among smoking mothers with the CYP1A1 Aa/aa and GSTT1 absent genotypes (-1285 g; P <.001). Genotype did not independently confer and adverse effect in never-smoking mothers. A similar pattern was observed in analyses stratified by maternal ethnicity and in analyses for gestation.

Conclusion: Maternal CYP1A1 and GSTT1 genotypes modified the relationship between maternal cigarette smoking and infant birth weight, indicating an interaction between metabolic genes and cigarette smoking.