The updated review suggests participating in diet or exercise interventions during pregnancy does, in fact, improve outcomes for both mother and child.
The updated review is published in The Cochrane Library and incorporates evidence from 37 new studies that were published between October 2011 and November 2014.
According to the American Congress of Obstetricians and Gynecologists (ACOG), the past decade has seen an increase in women who are overweight or obese at conception.
In fact, data collected by the National Center for Health Statistics (NCHS) from 1999-2004 reveals that almost two thirds of women who were of childbearing age were classified as overweight (a BMI of 25 kg/m2) and nearly one third were obese (BMI ≥30 kg/m2).
Previous research has suggested that gaining too much weight during pregnancy can increase risks of gestational diabetes, high blood pressure, large babies and birth interventions. Meanwhile, newborns who are born with large birth weights have a higher risk of childhood obesity.
Diet or exercise, or both, improved outcomes
The latest review uses evidence from 11,444 women across the new studies and suggests diet or exercise interventions - or a combination of both - can prevent excessive weight gain during pregnancy.
- Underweight women (BMI 2) at start of pregnancy should gain 28-40 lbs
- Normal weight women (BMI 18.5-24.9 kg/m2) should gain 25-35 lbs
- Overweight women (BMI 25-29.9 kg/m2) should gain 15-25 lbs
- Obese women (BMI >30 kg/m2) should gain 11-20 lbs.
In detail, only 36% of women who participated in the interventions gained excessive weight during their pregnancy, compared with 45% of women in the groups that did not take part in any intervention.
The diet interventions consisted of low-sugar diets, while the exercise interventions consisted of moderate intensity exercise, including walking, aerobics, Pilates and dance.
The women who took part in the interventions were less likely to have high blood pressure, and, interestingly, they were also slightly less likely to have a Cesarean delivery (27% vs. 29%). These women likewise had reduced chances of having a large baby - defined as more than 4 kg (8.8 lbs).
Though the researchers in the review were not able to conclude whether supervised interventions were more effective than counselling interventions, they hope that data from other ongoing trials will be able to determine the answer soon.
The researchers note that a new World Health Organization (WHO) guideline on antenatal care is currently in development and will incorporate this latest evidence.
Lead author Prof. Benja Muktabhant, from the Department of Nutrition at Khon Kaen University in Thailand, says they "need more studies on the effectiveness of these interventions in low-income countries and in women with non-Western lifestyles."
Co-author Tess Lawrie adds:
"Pregnancy is a time when women have a lot of contact with health care providers, therefore there is no better time to engage and support women to make healthy lifestyle choices.
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."