Is the intra-uterine period really a critical period for the development of adiposity?

Abstract

Objective: The intra-uterine environment may be a critical period for the development of adiposity. Alternatively, most of the co-variance of relative weight from birth to adulthood may be genetic in origin. This study tested whether birth weight 'tracks' into adulthood, independent of genetic factors.

Design: Observational twin study. Birth weights and gestational ages from birth records of 8040 twins from the Minnesota Twin Registry including 699 monozygotic (MZ) male pairs, 609 dizygotic (DZ) male pairs, 939 MZ female pairs, 880 DZ female pairs, and 893 opposite sex DZ pairs ages (yrs) 28 to 52 (Mean = 40.3; s.d. = 6.2) were compared to self-reported adult height and weight.

Results: The correlation of birth weight with adult height was 0.236, with adult weight 0.188, and with adult body mass index 0.078 (all P-values < 0.0005). To test if this tracking was independent of genetic influences, we analyzed intra-pair differences for MZ twins. If differences in birth weight between members of a MZ twin pair correlate with adult relative weight, this association cannot be attributed to genetic influences. The correlation of intra-pair differences in birth weight with intra-pair differences in adult height was 0.316 (P < 0.0005), with adult weight 0.136 (P < 0.0005), and with adult BMI 0.026 (P = 0.331). Results were unchanged when multivariate regression modeling was employed.

Conclusion: These data suggest that the intra-uterine environmental influences on birth weight have an enduring impact on adult height but not on adult relative weight. This suggests that the intra-uterine period is a critical period for the development of height but not for adiposity.