“Is eating for two” a good idea? Maintaining a healthy weight during pregnancy helps mother and baby

Pregnant women can improve their health and even reduce the risk of complications during childbirth by maintaining a healthy weight through diet and exercise. Research has shown that gaining too much weight during pregnancy increases the risk of gestational diabetes, high blood pressure, large babies, and delivery by caesarean section; and newborns with large birth weights are at risk of childhood obesity.

An updated systematic review published in The Cochrane Library reveals that diet or exercise interventions, or a combination of both, can prevent excessive weight gain in pregnancy. The original version of the review published in 2012 found only inconclusive evidence, that dietary and exercise programs had beneficial effects for pregnant women and their babies. In the updated version of the review, the research team incorporated evidence from 37 new studies published between October 2011 and November 2014. The review findings are now based on evidence from 11,444 women.

Researchers found that around 36% of women who were allocated to interventions to help them manage their weight, had excessive weight gain over the course of their pregnancy compared with around 45% in the control groups. Interventions involving low sugar diets, exercise only, or diet and exercise combined, all led to similar reductions in the number of women gaining excessive weight. Exercise interventions were mainly of moderate intensity and included various individual or group activities such as walking, aerobics, Pilates and dance.

Women receiving the interventions were less likely to be found to have high blood pressure. In addition, evidence suggested that the interventions may lead to a small reduction in caesarean deliveries from 29% to 27%, and reductions in the chances of having a baby with a large birthweight (more than 4 kilograms). Reviewers were unable to determine whether supervised interventions were better than counselling interventions and data from several ongoing trials will hopefully answer this question in the future.

“The review’s findings will be important for informing antenatal care guidelines,” said lead author Benja Muktabhant, an Associate Professor in the Department of Nutrition at Khon Kaen University, in Thailand. “However, we need more studies on the effectiveness of these interventions in low-income countries and in women with non-Western lifestyles.” A new World Health Organization (WHO) guideline on antenatal care is in development and is expected to include recommendations based on this evidence.

“Pregnancy is a time when women have a lot of contact with healthcare providers, therefore there is no better time to engage and support women to make healthy lifestyle choices,” said co-author Tess Lawrie. “We hope that these findings will encourage women not to overeat and to exercise regularly with the knowledge that their efforts will be rewarded with lower pregnancy weight gain and better health outcomes for themselves and their baby.”

The researchers advise that pregnant women should refer to the Royal College of Obstetricians and Gynaecologists guidelines on exercise in pregnancy, and that before embarking on a new exercise program that they discuss it with their midwife or doctor.

Editor’s notes:

According to NHS choices, most women with a singleton pregnancy gain between 10 and 12.5 kgs during pregnancy, with most of this gain occurring in the second half of pregnancy. A gain of more than 12 kg is used by some as a rough rule of thumb to be 'excessive' but this does not take into account a woman's baseline/pre-pregnancy weight. Some countries have more specific guidelines according to pre-pregnancy body mass index. Most of the included studies used Institute of Medicine (USA) guidelines which are as follows:

For women who are underweight at the start of pregnancy (BMI< 18.5 kg/m2): recommended to gain 28 lbs to 40 lbs (12.5kg to 18kg)

For women who are normal weight at the start of pregnancy (BMI 18.5 to <24.9kg/m2) : recommended to gain 25 lbs to 35 lbs (11.5kg to 16kg)

For overweight women (BMI 25kg/m2 to <29.9kg/m2): recommended to gain 15 lbs and 25 lbs (7kg to 11.5 kg)

For obese women (BMI > 30kg/m2): recommended to gain 11 lbs and 20 lbs (5 to 9kg)

Full citation: Muktabhant B, Lawrie TA, Lumbiganon P, Laopaiboon M. Diet or exercise, or both, for preventing excessive weight gain in pregnancy. Cochrane Database of Systematic Reviews 2015, Issue 6. Art. No.: CD007145. DOI: 10.1002/14651858.CD007145.pub2

Access the Spanish version of the review here.