The effect of birth weight on risk factors for coronary heart disease in adult twins
The aim of this study was to assess whether pre-natal growth restriction due to intra-uterine factors influences risk factors for coronary heart disease in adult life. 131 pairs of same-six (60 MZ and 71 DZ) twins aged 19-50 years and 89 singleton controls matched for sex, gestational age, maternal age and parity were recruited from a local obstetric database. Measurements were made of height, weight, waist circumference, body fat and blood pressure, and a fasting blood sample was taken for measurements of cholesterol, triglycerides, apolipoproteins, fibrinogen, glucose and insulin. Smoking, diet, physical activity and medical details were obtained by questionnaire, and an ECG was recorded. The birth weight difference between twins ranged from 0-1840g, with a mean within-pair difference of 337g. The overall results suggest that twins do not have an increased risk of coronary heart disease despite their considerably smaller size at birth and substantial catch-up growth. There was no evidence of differences between MZ and DZ twins in either unpaired or paired analysis of birth weight and adult risk factors apart from total cholesterol which was significantly negatively associated with birth weight in DZ twin pairs. Birth weight was inversely associated with cardiovascular risk factors in controls, whereas the associations were inconsistent in twins. The relationship between birth weight and cardiovascular risk factors was stronger in controls than in twins, which indicates that the effect of birth weight in twins is different to that in singletons. The results of this study suggest that growth restriction in mid to late gestation, as a result of inter-uterine factors, does not lead to an increased risk of coronary heart disease in adult twins up to 50 years. This is possibly due to factors influencing birth weight in twins, which do not operate in singletons.