Analysis: Exercise with a weight control diet for those who are pregnant is healthy for both baby and mom-to-be., though may or may-not produce better clinical outcomes.

Weight-Control Diet for Mom Builds a Better Baby

 

By Rita Baron-Faust, Contributing Writer, MedPage TodayPublished: May 17, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco.

A healthy, calorie-controlled diet to reduce excess weight gain during pregnancy is not only safe for mother and baby but also can improve pregnancy outcomes compared with exercise alone or a combination of the two, a meta-analysis showed.

 

The analysis of randomized trials conducted among more than 7,000 women showed that a calorie-restricted healthy diet limited gestational weight gain by a mean difference of -3.84 kg, or about 8.4 lbs. (95% CI 11.5 lbs. to 5.4 lbs., P<0.001) compared with other interventions, and improved pregnancy outcomes for mother and baby, the researchers wrote online in BMJ. 

Although adhering to a diet produced the biggest benefits, any of the interventions limited excess weight gain during pregnancy by -1.42 kg, around 3.1 lbs. (95% CI 2 lbs. to 4.1 lbs., P<0.001) compared with controls, wrote Shakila Thangaratinam, PhD, MRCOG, of the University of London, and co-authors.

One explanation for the effectiveness of diet could be that "interventions with one main component like diet may be delivered to a higher standard compared to the mixed group (and) the simplicity and perceived safety of diet than other methods," Thangaratinam wrote in an email to MedPage Today.

Noting that obesity during early childhood can persist into adulthood, and that prenatal visits are an ideal time to motivate expectant mothers to make lifestyle changes to improve outcomes for themselves and their babies, the authors decided to investigate which weight management interventions were the most effective and safe during pregnancy.

Retaining postpartum weight is also associated with adverse health outcomes in later pregnancies, Thangaratinam noted in her interview.

To collect relevant studies, the team conducted a literature search of databases (including Medline and the Cochrane Database of Systematic Reviews) and ranked the outcomes, primarily weight changes in the mother and baby.

They selected 44 relevant, randomized controlled clinical trials conducted among 7,278 women in institutions in the U.K., Poland, the Netherlands, and Switzerland, including women with gestational diabetes.

The trials involved three interventions: diet, physical activity, and a mixed approach that may have included behavioral counseling.

Overall, there was a reduction in preeclampsia by 26% (RR 0.74, 95% CI 0.60 to 0.92; P=0.006). Trends towards reduction in gestational diabetes, gestational hypertension, and preterm delivery were deemed not significant.

Only the dietary intervention produced a 33% reduced risk of preeclampsia (RR 0.67, 95% CI 0.53 to 0.85; P<0.001) and a 61% reduced risk of gestational diabetes (RR 0.39, 95% CI 0.23 to 0.69; P=0.001). It also produced nonsignificant reductions in gestational hypertension (RR 0.30, 95% CI 0.10 to 0.88; P=0.03) and preterm delivery (RR 0.68, 95% CI 0.48 to 0.96; P=0.03).

Among women with gestational diabetes, "although a positive benefit was reported for preeclampsia and gestational hypertension, the quality of evidence for these measures was rated as low or very low," noted Lucilla Poston, PhD, of St. Thomas Hospital in London, in an accompanying editorial.

There were no differences in these outcomes with physical activity alone and the mixed approach intervention compared with controls.

Poston disagreed with the authors' conclusion that diet and exercise interventions improved pregnancy outcomes. "This excellent review does not show with any degree of certainty that interventions in pregnancy have been shown to improve clinical outcomes, especially reducing high birth weight, which is one of the most important problems," she commented in an email interview with MedPage Today.

In fact, compared with controls, there was a nonsignificant reduction (mean difference -50 g or 1.76 oz, 95% CI 100g or 5.5 oz to 0 g) in birth weights.

As for safety to the baby, 15 of the trials (involving 3,905 newborns) showed trends towards reductions in intrauterine death, birth trauma, and hyperbilirubinemia. The overall risk of shoulder dystocia during birth was reduced by 61% with all interventions compared with the control group. There were no differences between the groups for respiratory distress syndrome or admission to a neonatal intensive care unit.

It would be premature to change guidelines for weight gain in pregnancy based on this analysis, said Poston in her interview.

"Some of the studies were small and of low quality. The authors did not include evidence for an effect on postpartum weight retention (presumably through lack of adequate data), which has been shown to be robustly associated with excessive gestational weight gain," Poston wrote in her BMJ editorial.

Limitations of this analysis included lack of data on risk factors such as age, ethnicity, and socioeconomic status.

This study was funded by the National Institute for Health Research Health Technology Assessment U.K. program.
The authors declared that they had no competing interests.

Primary source: BMJ
Source reference:
Thingaratinam S "Effects of interventions in pregnancy on maternal weight and obstetric outcomes: meta-analysis of randomised evidence" BMJ 2012; 344: e2088.
Additional source: BMJ
Source reference:
Poston L, Chappell L "How should women be advised on weight management in pregnancy? BMJ 2012; 344: e274.