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The University of Southampton

Study shows maternal weight at the start of pregnancy linked with increased risks of complications

Published: 8 May 2019
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These findings have major implications for health care during pregnancy.

New research shows that maternal weight status at the start of pregnancy, rather than weight gain during pregnancy, is strongly related to the risk of pregnancy complications for mothers and infants.

Obesity among women of reproductive age is a major problem for society. Results from this new study, involving the University of Southampton and published in JAMA, showed that overweight and obesity at the start of pregnancy are highly prevalent.

Pregnancy complications in mothers and their infants occurred in 34 per cent of women with a normal weight and in more than 60 per cent of women with severe obesity at the start of their pregnancy.

Of all women with very severe obesity and a high amount of gestational weight gain, over 90 per cent experienced pregnancy complications. The amount of weight gain during pregnancy had a much smaller effect on the absolute risk of these pregnancy complications than weight before pregnancy.

These findings have major implications for health care during pregnancy and at delivery. Rather than focusing on maternal weight gain during pregnancy, strategies are needed to optimize maternal weight before the start of pregnancy to improve pregnancy outcomes.

These findings are the result of a large-scale international collaboration, led by the Erasmus MC, University Medical Center, Rotterdam. The authors analysed more than 190,000 mother and child pairs from 25 studies from Europe and the USA.
Keith Godfrey, Professor of Epidemiology and Human Development at the University and part of the research team, said: “A large amount of evidence indicates that achieving a healthy weight prior to conception is of paramount importance in reducing the risk of pregnancy complications and helping the next generation to have the best life chances.

“The new findings demonstrate the serious implications of the ongoing epidemic of obesity for individuals. The findings stress the importance of developing new interventions before and during pregnancy to reduce the risks of maternal obesity for the mother and her baby, and to help mothers achieve a healthy weight prior to conception.

“Public Health England have published a suite of resources which can help in planning and preparation for pregnancy to improve outcomes for mothers and babies – major initiatives are needed to apply these throughout the health care system.

“Our findings highlight the importance for further studies focused on the optimal amount of gestational weight gain among severely obese women, also including adverse outcomes such as still birth and infant death, which were not available in our study. We believe that our findings should be considered by future updates of clinical guidelines.”

The research involved more than 60 international researchers from 16 countries who work together in the EU Horizon 2020 funded LifeCycle Project – Maternal Obesity and Childhood Outcomes Group. The LifeCycle Project is a large collaboration focused on innovative research on the role of novel integrated markers of early-life stressors that influence health across the lifecycle using an open and long-term network of pregnancy and birth cohorts. 

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