Pregnant women who put on too much weight are more likely to die of conditions like heart disease and diabetes than those who follow recommended guidelines, according to a study led by researchers at the University of Pennsylvania.
Some weight gain during pregnancy is expected and considered healthy. Most of it comes during the third trimester as the baby grows and the body holds extra water, in addition to the placenta and amniotic fluid. Healthy weight gain during pregnancy helps some women avoid complications during childbirth, the American Pregnancy Association says.
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The amount of weight women should gain during pregnancy is directly linked to their weight at the start of pregnancy. The current guidelines were established in 2009 by the National Academy of Medicine and use body mass index as a benchmark, as shown in the chart below.
| Pre-Pregnancy Body Weight | Recommended Weight Gain |
| Underweight (BMI less than 18.5) | 28-40 pounds |
| Normal (BMI between 18.5-24.9) | 25-35 pounds |
| Overweight (BMI between 25-29.9) | 15-25 pounds |
| Obese (BMI of 30 and above) | 11-20 pounds |
Nearly half of pregnant women gain more weight than is recommended by these guidelines, according to one large study in the Journal of the American Medical Association.
The Penn study, published in The Lancet, found that too much weight gain during pregnancy led to a higher risk of death among all women except those who already were obese. The study examined 50 years of data, following women from the time they gave birth.
Underweight women who put on too much weight were 84% more likely to die of heart disease. Among women of normal weight — about two-thirds of the 45,000 followed in the study — the risk of death from any cause rose by 9%. Their risk of dying of heart disease increased by 20%.
Among overweight women, the risk of death increased by 12%. They were 12% more likely to die of a diabetes-related death. Obese women may not have had an increased risk of death from weight gain because their risk already is elevated, the researchers said.
Some pregnant women develop gestational diabetes, a type of insulin resistance that results from the placenta producing hormones that affect blood sugar levels. Although gestational diabetes can affect women of all body types, overweight and obese women have a higher risk of developing it and having childbirth complications. The condition often goes away after the baby is born and excess weight is lost, but about 50% of women with gestational diabetes later develop type 2 diabetes, according to the U.S. Centers for Disease Control and Prevention.
Women who are overweight or obese often are advised to lose weight before pregnancy to decrease their risk of gestational diabetes. If they already are pregnant, it's often recommended that they work with a doctor on a weight management and exercise plan that ensures the health of themselves and their babies.
The Penn researchers noted that weight gain during pregnancy can be influenced by a number of factors, including access to health care and stress. Pregnant women should strive for healthy weight gain during the course of their pregnancies.
"We hope that this work leads to greater efforts to identify new, effective, and safe ways to support pregnant people in achieving a healthy weight gain," said Stefanie Hinkle, the study's lead author and an assistant professor of epidemiology and obstetrics and gynecology at Penn. "We showed that gaining weight during pregnancy within the current guidelines may protect against possible negative impacts much later in life, and this builds upon evidence of the short-term benefits for both maternal health and the health of the baby."