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Diet and exercise during pregnancy: benefits-focused discussion needed a bit more balance on harms


3 Star


Exercise, diet or both may protect against excess pregnancy weight

Our Review Summary

pregnancy exerciseThe story recaps a recent paper that reviewed the medical literature on the effect of exercise and diet programs on pregnant women. The story reports that women who took part in exercise, diet programs, or both, were less likely to gain too much weight during pregnancy. And it does a good job of defining the guidelines for weight gain during pregnancy for women of different body weights. However, the story could have quantified the potential benefits of diet and exercise programs in a more precise and meaningful way. In addition, it suggests that such programs reduce the risk of other health-related outcomes without clarifying the variability of evidence to support those claims (many results for these benefits were not statistically significant). The story also didn’t note that diet and exercise programs increased the risk of low pregnancy weight gain, which, like excessive weight gain, is associated with a variety of adverse health effects.


Why This Matters

The United States has an obesity problem, with more than a third of adults (and 17 percent of children) qualifying as obese. Obesity increases risks for a wide range of health problems, such as heart disease and diabetes, and is associated with significantly higher health care costs. There is some evidence that obesity during pregnancy makes it more likely that the baby will develop heart disease or diabetes later in life. At the same time, expecting parents often seek out things they can do to give their child the best possible start in life. Should they exercise? Should they adopt a specific diet? What’s best for mom? What’s best for baby? This is a subject with national health implications, and an audience that is eager for information that will allow them to make important health decisions. That makes it especially important to cover the subject clearly and thoroughly.


Does the story adequately discuss the costs of the intervention?

Not Applicable

The story doesn’t address costs. But the interventions are so broadly defined that it would be difficult or impossible to address cost in a meaningful way. We’ll rate this not applicable.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The story reports that women who took part in “diet, exercise or combination programs were about 20 percent less likely than women in standard-care groups to gain too much weight.” And the story does a nice job of articulating that there is significant variation in how much weight is “too much,” depending on the mother’s weight prior to pregnancy. However, the absolute reduction in risk was also reported in the study tables, and so we would’ve expected the story to cite that information. The study reported that excessive weight gain would be expected in 452 of 1000 women in the standard care groups compared with 362 per 1000 in the diet and exercise groups — that’s the 20% reduction mentioned in the story.

The story also wasn’t quite as clear as it could have been when discussing other potential benefits of diet and exercise. For example, the story says “There was no clear benefit among the women in the diet and exercise groups when the researchers looked at other complications, such as cesarean delivery, but it did look like there may be some benefit, they write.” That statement is a little confusing. To clarify, the article could have said something like: Women who participated in combined diet and exercise programs were 13% less likely to have a C-section compared to women who did not, though this difference was not quite statistically significant — in other words, it may have arisen by chance.

Does the story adequately explain/quantify the harms of the intervention?

Not Satisfactory

This one was borderline but ultimately deemed Not Satisfactory. The story addresses harms through quotes from an independent source who specializes in high-risk pregnancy. She says it “was very reassuring that [the paper says] there wasn’t an increased risk of preterm birth with moderate exercise.” However, we’d note that the paper itself says that, while there was no difference between groups with regard to preterm birth overall, “Limited evidence suggested that [the effect] may differ…with a trend towards an increased risk for exercise-only interventions.” That’s not quite as reassuring as the source suggests, and we think the result deserved some discussion. In several places, the study authors noted that the issue of preterm birth needs more research so that safe guidelines can be established.

A related concern is that there’s no acknowledgment of the increased risk of low gestational weight gain seen in the diet and exercise groups or the associated harm that inadequate weight gain could potentially cause. Only the benefits of reducing excessive weight gain are discussed. To the story’s credit, it does state the importance of talking to your doctor before starting a diet or exercise regimen.

Does the story seem to grasp the quality of the evidence?


Another close one. The story states that “the researchers examined data from 65 randomized controlled trials, which are considered the ‘gold standard’ of medical research. They were able to combine data from 49 trials involving a total of 11,444 pregnant women.” Good. The story also says “the new review found ‘high quality evidence'” — not as good. The story never defines what it means by “high-quality evidence,” and we think that description could be somewhat misleading, since the paper notes that 20 of the studies it looked at were “at moderate-to-high risk of bias.” The paper also differentiated between findings for which it had “high-quality evidence” (those studies found “no clear difference” on excessive birth weight) and those for which it had “moderate-quality evidence” (those studies found that women in diet or exercise programs had less weight gain) — a distinction the story didn’t address.

With that being said, we acknowledge that it would have been difficult for the story to get into the details that would have clarified these issues, and we think the coverage is generally on target. We’ll give the benefit of the doubt here and award a Satisfactory.

Does the story commit disease-mongering?

Not Satisfactory

Generally speaking, the story treats excessive weight gain during pregnancy as a disease in itself, rather than as a risk factor for other health problems. Where it does explicitly state that gaining too much weight is linked to “an increased risk of complications,” it doesn’t tell readers what those complications might be.

Does the story use independent sources and identify conflicts of interest?


The story cites an independent source and makes it clear when quoting from the paper itself.

Does the story compare the new approach with existing alternatives?

Not Applicable

The categories here — diet and exercise — are so broad as to cover most (if not all) of the options that could be recommended to a pregnant woman for limiting weight gain during pregnancy.

Does the story establish the availability of the treatment/test/product/procedure?

Not Applicable

It might have been useful to give readers a sense of whether diet and/or exercise programs are routinely available to pregnant women (either through their obstetricians or in the community). However, we won’t penalize the story for not addressing this, since it’s also possible to exercise without any supervision.

Does the story establish the true novelty of the approach?


The story makes clear that this paper is an update to a previous review, published in 2012, that did not find conclusive evidence to support claims of health benefits from diet and exercise programs during pregnancy.

Does the story appear to rely solely or largely on a news release?


The story cited at least one independent source and drew on material from the Institute of Medicine.

Total Score: 4 of 7 Satisfactory

Comments (3)

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Adam Trainor

June 20, 2015 at 4:42 am

I do think that women who are pregnant should take their diet into consideration, whether that’s watching what they eat or changing their diet completely. It will help them and the baby. I don’t agree with this, “Women who participated in combined diet and exercise programs were 13% less likely to have a C-section compared to women who did not” This is not true at all, it all depends on how the baby is positioned too. Shouldn’t the womans body be taking into consideration whether she will gain excess baby weight? I have known women who have been really slim before their pregnancy and after their pregnancy they have gone back to their slim frame.


    Gary Schwitzer

    June 20, 2015 at 8:52 am


    Thanks for your note.

    Allow me to ask for clarification about your comment that you don’t agree with the “13% less likely to have a C-section” line, and your further comment that “this is not true at all.”

    That’s the reported finding from the published study.

    Are you questioning the methodology of the study? Otherwise, saying you don’t agree with it – and that it’s not true at all – without citing any evidence, feels a bit empty.


      Adam Trainor

      June 22, 2015 at 12:54 pm

      Sorry I do apologise I have stepped the mark there and used the wrong words. I’m not questioning the methodology of the study, reseachers have probably found this out thats why you included it in the post. I am disagreeing with this study.