Background This study attempted to clarify the household and mother's lifestyle factors that contribute to the greater fetal vulnerability of African-American individuals to airborne polycyclic aromatic hydrocarbons (PAH).

Methods Non-smoking pregnant women with no known risks of adverse birth outcome were monitored for their personal exposure to airborne PAH. Birth outcomes were collected from the hospital medical record. Modification of the airborne PAH effects was statistically examined. In linear regression analyses, modification of PAH effect by demographic, socioeconomic and behavioural traits on birth weight and fetal growth ratio were respectively tested, adjusting for the gestational age, gender, parity, delivery season, maternal body mass index and weight gained during the present pregnancy.

Results Maternal obesity exacerbated the airborne PAH risk by −491 g per 25th to 80th percentile unit exposure (95% CI −197 to −786 g; p<0.01) among African Americans. In addition, frequent dietary intake of smoked, grilled or barbequed items independently reduced the birth weight of African-American newborns by −204 g (95% CI −21 to −387 g; p=0.03).

Conclusion Maternal obesity significantly exacerbated the risk of prenatal PAH exposure in African-American newborns. Also, frequent dietary consumption of PAH-laden food items posed an independent risk on the reduced birth weight among African Americans.