Intrauterine, environmental, and genetic influences in the relationship between birth weight and lipids in a female twin cohort

Objective - To investigate the association between birth weight and lipid levels in a cohort of UK female twins. Methods and Results - Birth weights and fasting blood lipid levels were available for 2900 women aged 18 to 80 years. Individual level regressions indicated that a 1-kg increase in birth weight was associated with a 0.08-mmol/L decrease in total cholesterol (95% confidence interval [CI], -0.12, -0.04) and a 0.06-mmol/L decrease in low-density lipoprotein (-0.10, -0.03). Using a regression model that includes both mean twin pair birth weight and individual twin's difference from the pair mean, we found that these significant relationships were between twin pairs only and not within pairs. We found no significant relationships for high-density lipoprotein. When monozygotic and dizygotic twins were analyzed separately we found similar effect sizes. Restricting the analysis to postmenopausal women we found stronger relationships between birth weight and lipid levels, which was attenuated after adjustment for body mass index (BMI). Conclusions - These novel results suggest that significant relationships between birth weight and lipids are mediated through shared influences on the maternal environment and do not support the hypothesis that fetal malnutrition is an important determinant of adult lipid levels. Adjustment for BMI also indicates that postnatal growth may be more important than prenatal growth.