It is the first time that a link has been identified between greater weight gain in the weeks following birth and impaired lung development.
But infant feeding products, previously blamed for rapid weight gain after birth and tendency to obesity, are not considered responsible for the impact on respiratory health, according to the researchers. The weight gain should be seen merely as a 'catch-up phase'.
"It is unlikely that different types of feeding could be responsible for this effect. Somewhat surprisingly, the findings did not appear to reflect either whether the baby was breast or bottle-fed, or the known harmful effects of smoking during and after pregnancy," said study leader Dr Jane Lucas of the University of Southampton's School of Medicine.
"We are more inclined to think that the post-natal weight gain of some babies could represent a catching-up process, a consequence of growth restriction in the later months of pregnancy. That would mean that the foetus' lungs had not reached their normal dimension, which would contribute to reduced lung function," she added.
The study, published in the 1 September issue of the American Journal of Respiratory and Critical Care Medicine (170: 534-540), measured various lung function parameters in 131 healthy babies aged from five to 14 weeks, some with a birthweight below the norm. The researchers also recorded the speed with which the babies gained weight.
Both a lower birthweight and a greater weight gain in the early weeks after birth were associated with reduced respiratory capacities.
The findings suggest that improving a baby's lung growth and development before and after birth could have lifelong benefits for its respiratory health.
Dr Lucas told NutraIngredients.com: "We haven't yet analysed the maternal diet data from this study yet but there might well be aspects of the maternal diet affecting the baby's micronutrient intake or overall health that influence this outcome."
Professor John Warner from Southampton University's School of Medicine added: "While the relationship of low birth weight and reduced lung function has been recognised for many years, this is the first work to recognise the relationship between rapid infant weight gain and poor lung function. We believe the reduced lung function in these infants may have implications for susceptibility to later respiratory disease, in particular asthma."
The mothers of the babies taking part in this study are participating in the Southampton Women's Survey, a project studying the link between a mother's health and nutrition before and during pregnancy and the growth and development of their children.
Researchers increasingly believe that maternal nutrition can have a greater impact on an infant's health than previously thought. Other recent findings suggest that growth from the very earliest days in the womb affects health in adulthood, particularly the risks of heart disease, diabetes and osteoporosis.