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Genetic and Non-Genetic Factors Affecting Birth-Weight and Adult Body Mass Index

Published online by Cambridge University Press:  21 February 2012

John B. Whitfield ,
Susan A. Treloar ,
Gu Zhu  and
Nicholas G. Martin
John B. Whitfield
Affiliation:
Department of Clinical Biochemistry, Royal Prince Alfred Hospital, Sydney(1); Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane.
Susan A. Treloar*
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane. [email protected]
Gu Zhu
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane.
Nicholas G. Martin
Affiliation:
Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, Brisbane.
*
*Address for correspondence: Dr. Susan Treloar, Genetic Epidemiology Laboratory, Queensland Institute of Medical Research, PO Royal Brisbane Hospital, QLD 4029, Australia.

Abstract

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Birthweight affects neonatal mortality and morbidity and has been used as a marker of foetal undernutrition in studies of prenatal effects on adult characteristics. It is potentially influenced by genetic and environmental influences on the mother, and effects of foetal genotype, which is partially derived from the maternal genotype. Interpretations of variation in birthweight and associated characteristics as being due to prenatal environment ignore other possible modes of materno-foetal transmission. Subjects were adult twins recruited through the Australian Twin Registry, aged 17 to 87 years, and the sample comprised 1820 men and 4048 women. Twins reported their own birthweight as part of a health questionnaire. Body Mass Index (BMI) was calculated from self-reports of height and weight. Correlations between co-twins' birthweights were high for both monozygotic (r = 0.77) and dizygotic (r = 0.67) pairs, leading to substantial estimates of shared environmental effects (56% of variance) with significant additive genetic (23%) and non-shared environmental (21%) components. Adult BMI was mainly influenced by genetic factors, both additive (36% of variance) and nonadditive (35%). The correlation between birthweight and BMI was positive, in that heavier babies became on average more obese adults. A bivariate model of birthweight and adult BMI showed significant positive genetic (rg = 0.16, p = 0.005) and environmental (re = 0.08, p = 0.000011) correlations. Intra-uterine environmental or perinatal influences shared by cotwins exercise a strong influence on birthweight, but the factors which affect both birthweight and adult BMI are partly genetic and partly non-shared environmental.

Type
Articles
Information
Twin Research and Human Genetics , Volume 4 , Issue 5 , 01 October 2001 , pp. 365 - 370
Copyright
Copyright © Cambridge University Press 2001