Too Much Pregnancy Weight Sets up Babies for Obesity

Obesity starts in the womb, says a recent study published in the Lancet and covered this week in The New York Times. We know that moms who gain a lot of weight in pregnancy are more likely to have heavy babies, but the question has always been whether it’s because they share common genes, and therefore weight tendencies.

Shared genes don’t explain it, though. In the current study, the scientists followed moms over consecutive pregnancies–same gene pool, different results. Women who put on more than 53 pounds were over twice as likely to have a baby weighing at least 9 pounds than moms who gained between 18 and 22 pounds.

Birthweight is related to adult weight, so scientists and public health officials think weight gain in pregnancy may be contributing to the overall rising incidence of obesity. In a related study of 9-year-old children, those kids of moms who had gained more than the recommended amount of weight in pregnancy were heavier, more likely to be overweight, and had more risk factors for heart disease, like higher blood pressure and lower “good” cholesterol.

Telling moms not to gain too much weight is touchy, but more doctors seem to be doing it. My friend (who is very active, on the slim side, and pregnant with her third baby) told me this week that her OBGYN recommended she gain no more than 20 pounds. Could the recent science of obesity and babies be changing how doctors advise moms during pregnancy? How much are we supposed to gain?

The current recommendations are that moms with low BMIs gain between 28 and 40 pounds; normal BMI moms gain 25 to 35 pounds; overweight moms, 15 to 25 pounds; and moms considered obese, 11 to 20.

The standards are considerably looser than they were a few decades ago, when most moms were told not to gain more than 15 to 20 pounds. The limits have since been raised, but beyond that, more than 60 percent of moms gain more weight than is recommended.

The biology isn’t completely clear, but a baby’s metabolism is likely to be influenced and programmed by a moms diet. And it’s not just weight gain during pregnancy, say the researchers, but gaining pounds before getting pregnant affects a child’s weight too.

Public health researchers are looking earlier and earlier to understand rising obesity rates–for example, as fellow blogger Paula Bernstein notes today, babies who don’t sleep enough are more likely to be obese too. Now we have to consider how the trend starts even before birth.

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