Achieving a healthy weight before becoming pregnant can significantly reduce the risk of the baby dying in his or her first year of life, a new study finds.

One in three women start pregnancy at an unhealthy weight, and more than half of women gain either too much or too little weight during pregnancy, according to researchers from the University of Pittsburgh Graduate School of Public Health. Their findings highlight the need to address obesity among women of reproductive age, the team says.

For the study, the researchers analysed records from more than 1.2 million births that occurred from 2003 to 2011 in Pennsylvania, including more than 5,500 infant deaths. The team classified mothers included in the data as underweight, normal weight, overweight or obese based on their pre-pregnancy body mass index or the measurement of weight versus height.

In each weight group, the researchers also examined the impact on infant mortality when women gained significantly more or less weight during pregnancy. They used the Institute of Medicine guidelines, which, for example, recommend a weight gain of 25 to 35 pounds for normal-weight women and 11 to 20 pounds for obese women.

The researchers found that in all the weight classes, except the most obese, gaining less than or much more than recommended increased the risk of infant death. Obese women were found to be more problematic, as even when they achieved the optimal weight during pregnancy, their risk of infant death was still about twice as great as that of those who began pregnancy at a normal weight.

To further establish the link between obesity and infant mortality, additional research needs to be conducted, the team noted.

“We are hopeful that this study can be used to start a dialogue between physicians and women on the importance of not only gaining a healthy amount of weight while pregnant but also reducing excess weight before they become pregnant as a potential way to improve infant survival,” said lead author Lisa Bodnar, associate professor in Pitt Public Health’s Department of Epidemiology.

"The team hopes information from the study empowers providers, including obstetricians, family doctors and primary care physicians, to discuss the benefits of preconception weight loss with all obese, reproductive-age women,” according to the study’s co-author Dr Katherine Himes, assistant professor in Pitt’s Department of Obstetrics and Gynecology.

In Australia, there were more than 1,000 infant deaths reported in 2012, according to the Australian Bureau of Statistics. Over the past 10 years, the number of infant deaths has generally decreased by more than 20 percent, with some fluctuation.

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