Ethnic Differences in the Association of Birth Weight and Blood Pressure: The Georgia Cardiovascular Twin Study

Background African Americans (AAs) not only have higher blood-pressure levels, but also an increased risk of low weight at birth, compared with European Americans (EAs). In light of fetal programming theories, it has been suggested that ethnic differences in blood pressure originate in utero. However, most previous studies in biethnic samples have not found a significant inverse association between birth weight and blood pressure in AAs. Methods In 562 EA and 465 AA adolescent twins of the Georgia Cardiovascular Twin Study, we investigated the potential ethnic difference in the association of blood pressure and birth weight, with the ability to control for potential confounding by familial factors. Results Blood-pressure levels were significantly higher in AAs compared to EAs, independent of birth weight (P< .01). After adjustment for parental factors and body mass index, the difference in systolic blood pressure per kg birth weight was −1.1 mm Hg (95% confidence interval, −2.7 to 0.48, P = .17) in EAs, and −2.5 mm Hg (95% confidence interval, −4.7 to −0.40, P = .02) in AAs. A significant ethnic interaction was revealed in paired analysis, where the inverse association remained in AAs, but not in EAs. Associations with diastolic blood pressure were generally weaker and nonsignificant. Conclusions We showed that low birth weight was associated with an elevated systolic blood pressure in AAs, independent of familial factors. The results also suggest that the association between birth weight and blood pressure may be more pronounced in AAs in adolescence.