News Release

Maternal factors may not be the key to birth weight association with cardiovascular disease

Peer-Reviewed Publication

BMJ

Association between birth weight and adult blood pressure in twins: historical study

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Within pair association between birth weight and blood pressure at age 8 in twins from a cohort study

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Two studies in this week's BMJ conclude that the function of the placenta may be more important than maternal factors, such as diet and smoking, in determining fetal development and the risk of cardiovascular disease in later life.

Babies with low birth weight have previously been shown to have higher levels of blood pressure as children, adolescents and adults. The two studies in this week's issue set out to examine whether this association is due to maternal factors, by examining the birth weights and subsequent blood pressure levels of twins [one twin is usually heavier than the other and, unlike separate singleton pregnancies, twins experience exactly the same maternal factors during pregnancy].

Professor Terence Dwyer and colleagues from the Menzies Centre for Population Health at the University of Tasmania studied 888 children until the age of eight years. They found an inverse relationship between birth weight and blood pressure within 55 twin pairs and conclude that because both twins have shared the same mother, maternal factors cannot be wholly responsible for birth weight and cardiovascular disease in later life.

They also found that in identical (monozygotic) twins [one twin usually still weighs more than the other] the twin with the lowest birth weight experienced higher blood pressure by the time they were eight years old and they therefore conclude that genetic factors are also unlikely to be responsible for the association. They believe that the link between restricted intrauterine growth and later blood pressure is more likely to be due to placental factors than to maternal nutrition.

In a separate study of 492 pairs of female twins (at that average age of 54 years), Dr Neil Poulter from Imperial College School of Medicine along with colleagues from Guy's and St Thomas's Hospital Trust in London, found that as in the children in Dwyer et al's study, twins who were heavier at birth had lower blood pressure as adults. Poulter et al report that as heavier and lighter twins are exposed to the same maternal diet, whilst not excluding the role of inadequate maternal nutrition, placental dysfunction is more likely to be the cause of retarded intrauterine growth, which leads to high blood pressure in later life.

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Contact:

Professor Terence Dwyer, Menzies Centre for Population Health Research, University of Tasmania, Hobart, Tasmania Tel: 61-3-6226-7700
Email: T.Dwyer@utas.edu.au

Dr Neil Poulter, Director, Cardiovascular Studies Unit, Department of Clinical Pharmacology, Imperial College School of Medicine, St Mary's Campus, London Tel: 44-171-594-3446
Email: n.poulter@ic.ac.uk


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