Pack on the pounds when you’re pregnant, and your daughter might pay the price when she’s older than you are now.
In a new study in the American Journal of Obstetrics & Gynecology, researchers found that middle-aged women whose mothers gained too much weight when they were pregnant were about three times more likely to be overweight than women whose moms didn’t gain too much weight.
And the daughters weren’t necessarily big babies at birth or overweight at age 4 or 20, which I found particularly surprising, given that previous studies showed women who gain too much weight while pregnant are more likely to deliver larger-than-average babies who grow into overweight kids. According to the authors, no one before had looked at the impact of excessive weight gain during pregnancy on sons or daughters beyond age 20.
While the mothers had delivered their daughters in the 1960s, the scientists classified them as having gained too much weight while pregnant based on 2009 recommendations from the Institute of Medicine, or the IOM. The IOM is part of the National Academy of Sciences, a private, nonprofit organization that provides independent advice on science and technology matters.
Believe it or not, the IOM’s previous recommendations, issued back in 1990, were more concerned with pregnant women not gaining enough weight for the health of their babies. But, as the authors of the new study write, the percentage of U.S. women of childbearing age who are overweight or obese has greatly increased over the last 30 years. And, they point out, four out of five of the mothers in their study gained more during pregnancy than what was commonly recommended back in the 1960s.
The IOM guidelines are based on your pre-pregnancy BMI, or body mass index, a measure of body fat based on height and weight. If you’re 5-foot-5, you could weigh anywhere between 111 and 150 pounds and have a BMI within the normal range.
The higher your pre-pregnancy BMI, the less weight you should gain during your pregnancy, according to the IOM. If your BMI is 30 or more, which is considered obese, the IOM recommends that you gain only 11 to 20 pounds during your pregnancy. But if your BMI is 18.5-24.9, which is considered normal weight, you should gain 25 to 35 pounds.
The 1,108 daughters in the new study had an average BMI of 27.02, which is overweight.
Previous research suggests that sons aren’t immune to the effects of their mothers gaining too much weight when pregnant. For example, overweight mothers who gained an excessive amount during pregnancy had sons with a higher BMI at age 18. One reason the new study focused on daughters is they were participants in a study about mammography and breast density. Other research has found a connection between fathers’ and children’s BMI, but studies of dads’ BMI and obesity in their adult children are limited, write the authors of the new study.
You probably don’t want baby fat to become a family heirloom, so if you’re thinking about having a baby and you’re overweight, it’s a good idea to try to slim down before you become pregnant. Being overweight or obese during pregnancy raises the risk of complications such as gestational diabetes and preeclampsia. If you’re already pregnant and overweight, talk to your doctor about how much more you can gain. As the March of Dimes notes, pregnancy is not the time to try to lose weight.