As the global obesity epidemic continues, more and more overweight and obese women are becoming pregnant. It is estimated that around 15-20% of pregnant women in the UK have a body mass index (BMI) higher than 30, which can have serious health consequences for both mothers and their children.

The consequences of obesity during pregnancy

Obesity poses risks to mothers throughout gestation and childbirth, as well as in the postpartum period. During pregnancy, the risk of gestational diabetes and pre-eclampsia is elevated in obese women, and those with a BMI over 30 are more likely to suffer miscarriages and infections. There are also many risks to babies born to obese women, including stillbirth, preterm delivery, congenital abnormalities and macrosomia. Later in life, children with obese mothers are more likely to be obese themselves, and suffer from related diseases such as type 2 diabetes.

So what can be done about maternal obesity?

The best way for mothers to protect their health and reduce risks to their children is to lose weight before becoming pregnant. However, this is not always possible; it is thought that around one in every six pregnancies is unplanned, and some women may not be aware of the risks associated with maternal obesity. Therefore, there is an urgent need for effective, short-term weight loss interventions that can be given during pregnancy.

In two related studies published in BMC Medicine as part of our Obesity: exploring the causes, consequences and solutions article collection, Jodie Dodd and colleagues from Adelaide University have tested the effectiveness of an intervention program for promoting healthy diet and physical activity during pregnancy. In the LIMIT randomized trial, overweight and obese pregnant women were assigned to receive either dietary and lifestyle advice – a comprehensive program involving a combination of dietary, physical activity and behavioral strategies – or standard care. In the authors’ analysis of maternal outcomes, those in the intervention group had improvements in their diet over the study period, such as increased fruit and vegetable consumption and reduced energy intake from saturated fats, as well as higher levels of physical activity than those receiving standard care.

Focusing on infant outcomes, Dodd and colleagues demonstrated that babies born to women receiving the intervention were less likely to have a birth weight of more than 4.5kg or suffer from respiratory distress syndrome when compared with those born to mothers receiving standard care. Taken together with previously published results showing that this lifestyle advice program is linked to lower incidence of high birth weight, these important findings from the LIMIT trial emphasize that interventions delivered during pregnancy can improve the health of mothers and their babies. Commenting on the research, Lucilla Poston suggests that improvements in maternal diet and activity occurring as a result of the lifestyle intervention could account for the beneficial effects seen in their infants.

Is diet linked to hypertensive disorders of pregnancy?

While the association between poor diet, obesity and hypertension is well-established, whether or not diet can influence the development of hypertensive disorders in pregnancy (HDP) is not fully understood. To address this question, Danielle Schoenaker and colleagues carried out a systematic review and meta-analysis of observational studies investigating the association between diet and pre-eclampsia. The authors showed that lower levels of dietary magnesium and calcium, as well as higher total energy intake, are related to pre-eclampsia. The authors caution that their meta-analysis is limited by the low number of studies included, but emphasize that:

“In line with existing guidelines, pregnant women should be advised to avoid excessive energy intake and excessive weight gain during their pregnancy. Furthermore, data suggest that higher calcium and magnesium intake and a diet rich in fruit and vegetables may be beneficial for HDP.”

These findings reinforce the benefits of eating a healthy diet, especially when planning a pregnancy, and highlight the importance of interventions such as those tested in the LIMIT trial for promoting healthy diet and lifestyle during pregnancy to improve the health of mothers and their babies.

Our Obesity: exploring the causes, consequences and solutions article collection is now open for research submissions. The collection covers all areas of obesity research, including clinical studies of new therapies and interventions, epigenetics and translational advances that contribute to understanding the causes and impact of obesity. If you have any research you would like us to consider for inclusion in this article collection, please email bmcmedicineeditorial@biomedcentral.com

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