Weight Gain in Pregnancy: How Much, How Little?

With new guidelines issued for weight gain during pregnancy, you may wonder whether the concern is women gaining too much or not enough. The answer is both. An eating disorder in which women are so afraid of weight gain that they reduce calorie consumption and exercise excessively puts their babies at risk. However, in the United States, the far more common problem is gaining too much weight during pregnancy, which can lead to short- and long-term risks for both mother and baby.

There’s no single perfect weight gain figure for all women but there are general guidelines. Yet some estimates say that as many as 70 percent of women do not keep weight gain within recommended boundaries.

Too little and too much gain both risky

Gaining more than 35 pounds puts normal weight women at increased risk for cesarean delivery, high birth weight babies and possibly preeclampsia. An American Institute for Cancer Research report found that baby girls of higher birth weight are probably more likely than those born at normal weight to develop premenopausal breast cancer as adults. Mothers are also likely to retain extra weight after pregnancy, raising their risk of a variety of health problems.

Gaining too little weight is also an immediate and long-term concern. Distorted body image views and books and Web sites promoting overly restrictive food choices may lead some women to gain unhealthfully little. Low birth weight babies are more vulnerable to infections and face increased risk of death and disease and also increased risk in adulthood of heart disease and diabetes.

For most women, the new recommendations don’t change their weight gain target, just the emphasis on achieving it. Underweight women (BMI less than 18.5) should gain 28 to 40 pounds during pregnancy; normal-weight women (whose BMI falls between 18.5 and 24.9) should gain 25 to 35 pounds; and overweight women (with BMI 25 to 29.9) should gain 15 to 25 pounds. Women carrying twins have higher weight gain targets.

New recommendations for obese women

The major change in recommended weight gain is for the estimated 28 percent of women of childbearing age who are now obese. Defined by a body mass index of 30 or more, at 5 feet 5 inches, this includes women 180 pounds and over.

Once urged to gain at least 15 pounds during pregnancy, experts now recommend obese women gain 11 to 20 pounds by eating a balanced diet (which may mean 2000 to 3500 calories a day). These women have fewer cesarean deliveries, develop diabetes or hypertension during pregnancy less often, retain less weight after birth, and are less likely to have a high birth weight baby compared to those who gain more.

Recommending more attention to weight before and during pregnancy

Because excessive weight gains are so common, the recommendations’ report emphasizes that women should aim to conceive while at a normal BMI and gain within the guidelines during pregnancy. More than half of U.S. women ages 20 to 39 are overweight or obese. In pregnancy, obese women are more likely than normal weight women to face gestational diabetes and hypertension, pre-eclampsia, birth defects, cesarean delivery and excessively large babies.

Find more from Karen Collins.

Karen Collins, D.C.N., M.S., R.D., serves as the nutrition advisor to the American Institute for Cancer Research (AICR). Karen writes two syndicated weekly columns, "Nutrition Notes" and "Nutrition-Wise," distributed by AICR. Karen was an expert reviewer for AICR's landmark international report, "Diet, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective," which provides recommendations based on an examination of more than 7,000 research studies by a panel of internationally renowned scientists. (Read her full bio.)