April 2021 Issue

Pregnancy Weight Gain
By Densie Webb, PhD, RD
Today’s Dietitian
Vol. 23, No. 4, P. 34

Today’s Dietitian reviews the current guidelines and provides expert counseling strategies for RDs.

One of the top concerns pregnant women have, aside from their baby’s health, is the amount of weight they gain during those nine months. Gaining an appropriate amount of weight during pregnancy can have a positive effect on fetal and maternal health during pregnancy, immediately postpartum, and even well into the future.1 Gaining too much or not enough can have serious health consequences for both mother and child. The question is, what is appropriate? How much is too much, and how much is too little?

In 2009, the Institute of Medicine (IOM) published guidelines on pregnancy weight gain that took into account the mother’s prepregnancy BMI, providing suggested total weight gain and weekly weight gain parameters during the second and third trimesters. While there’s no way to predict how much weight a woman ultimately will gain during pregnancy, weight gain during a first pregnancy often is, but not always, a good predictor of weight gain in subsequent pregnancies.2

Eating for Two?
“You’re eating for two now,” is a common refrain pregnant women hear from well-meaning friends and family. But they need to be reminded that they’re not eating for two adults. A full-term infant typically weighs between 7 and 8 lbs, only a small fraction of the weight of an adult. When “eating for two” is taken literally, it inevitably results in excessive weight gain. “The most difficult thing for pregnant women is when family members are trying to feed the pregnant mom,” says Melinda Scholten, RD, CDCES, dietitian at Nutrition Services and the Center for Women’s Health at NorthBay Healthcare in Fairfield, California, where she specializes in pregnancy nutrition. “The intentions are obviously caring, but it makes it so difficult for the mom.”

Scholten recommends a gradual weight gain of 1/4 lb to 1/2 lb per week but emphasizes that if a mom comes to see her and is already gaining too fast, she never tries to reach the previous goal by losing weight. Rather, the goal is to look forward to the due date and attempt to slow weight gain.

Just as there are guidelines for weight gain during pregnancy, there also are guidelines for how much more to eat to maintain a healthy pregnancy, and it isn’t as much as many women may believe. According to the Academy of Nutrition and Dietetics, extra calories aren’t required during the first trimester. During the second trimester, an additional 340 kcal per day are recommended. For the third trimester, the recommendation is 450 kcal more per day than when not pregnant.3 Those additional calories should, of course, come from nutrient-dense foods including fruits, vegetables, whole grains, lean proteins, and low-fat or fat-free dairy. See the “Daily Food Checklist” for pregnancy for single-serving sizes of these nutrient-dense foods patients should eat for each trimester, available from the USDA at wicworks.fns.usda.gov/wicworks/Topics/PregnancyFactSheet.pdf.

Maternal obesity is considered an epidemic health problem. In fact, obesity is the most common medical condition in women of reproductive age and, as such, represents an important preventable risk factor for negative outcomes on the long-term health of both mother and child.4,5 Maternal obesity is widely recognized for increasing the risk of developing gestational diabetes and preeclampsia, and of delivering infants that are large for gestational age, which can result in a difficult delivery.6 A systematic review found a clear association among women with obesity between weight gain during pregnancy and risk of large-for-gestational age infants.7 Compared with normal-weight pregnant women, pregnant women with obesity have an increased risk of miscarriage not only in the first trimester but also in subsequent pregnancies.8

“More than ever, women in the US are starting pregnancy with a BMI in the overweight or obese category, which puts them and their children at risk of insulin resistance, type 2 diabetes, preterm birth, pregnancy hypertension, structural birth defects independent of folic acid intake, postpartum weight retention, and a higher risk of obesity, diabetes, and hypertension in the child,” says Liz Ward, MS, RD, author of Expect the Best: Your Guide to Healthy Eating Before, During and After Pregnancy.

In the United States, overweight and obesity affect a large percentage of women of reproductive age, with 53.5% of these women having either condition.9 While guidelines for weight gain during pregnancy were issued in 2009 by the IOM and National Research Council, a study published in 2018 found that more than 50% of women with overweight and obesity gained above these recommendations during pregnancy.10-12 In addition, even the majority of women with normal prepregnancy BMIs gained above recommendations, especially in the third trimester. The study also found that women who were normal weight before pregnancy were more likely to gain weight within the guidelines than women who had obesity.12 Interestingly, weight gain above recommendations has been found to decline with the number of previous births.11

Increasing evidence also shows an association between maternal obesity and negative effects on the child’s health during childhood and later in life.5 Observational studies have suggested that maternal obesity can increase a child’s risk of obesity, coronary heart disease, stroke, type 2 diabetes, and asthma as an adult.5 Preliminary evidence even suggests potential effects on the immune system, higher risk of infectious diseases, and alterations in DNA that linger into adulthood.

Animal studies have shown that maternal obesity can permanently alter metabolic controls in the fetus, such as the physiology of pancreatic beta cells and the response to leptin, which is involved with appetite regulation.5 While the mechanisms to explain these changes are unclear, it has been suggested that inflammation, changes in placental function, and metabolism of glucose and fatty acids may play roles.13,14

It may seem self-evident, but some factors associated with excessive weight gain during pregnancy include low physical activity and eating a low-fiber, high-fat, high-sugar diet.1

Gaining Too Little
Gaining too little weight during pregnancy also is a problem, but not nearly as prevalent as excessive weight gain. The 2018 IOM study found that 21% of women gain too little weight during pregnancy and, not surprisingly, underweight women are the most likely to gain below recommendations.12

“When I was a new dietitian,” Scholten says, “I met a woman who said her doctor got mad if she gained too much weight. He told her 15 lbs max. We’ve come a long way since then.” But, she says, some doctors today have gone in the opposite direction and aren’t being cautious enough about weight gain in their pregnant patients, and gaining too much weight is much more of a problem.

If a woman begins a pregnancy with a BMI greater than recommended, she may be tempted to not gain weight or even lose weight. The weight gain of a normal pregnancy can be worrisome for some women, especially if they have a history of an eating disorder. However, according to Ward, “pregnancy is never a time to lose weight intentionally or to restrict calories. Inadequate calorie intake could mean inadequate nutrient consumption, which puts baby’s development at risk.” Evidence suggests that for women with severe obesity, low weight gain during pregnancy may increase the risk of small for gestational age infants or infant death.12

“We often see weight loss in the first trimester due to nausea and vomiting,” Scholten says. “In this case, we concentrate on trying to get as much nutrition as we can in a form that mom can tolerate. Then we work on weight gain from there.” For pregnant women who experience extreme, unrelenting nausea and vomiting (hyperemesis gravidarum), medical attention is required. Hyperemesis affects approximately 0.3% to 3% of pregnancies in the United States, and it’s the most common cause of hospitalization during the first half of pregnancy and can lead to miscarriage if not treated. Why it affects some women and not others is unknown.15

Bottom Line
It can be tempting for some pregnant women to want to keep weight gain to a minimum, but it isn’t recommended. But neither is pregnancy the time to throw caution to the wind and “eat whatever you want,” Scholten says. “It’s the time women should eat the best they’ve ever eaten.” That can be difficult when family and friends are encouraging pregnant clients to eat more, since they’re “eating for two.”

So-called “morning sickness” presents its own challenges. That nauseated feeling can linger long after morning and can greatly reduce appetite or, in extreme cases, make it impossible to keep food down. On the other hand, some pregnant women experience increased feelings of hunger or cravings that are satisfied only with intake of less nutritious foods, making it imperative that they’re provided guidelines for healthful eating, such as the aforementioned Daily Food Checklist.

“Exercise is also important,” Ward says, “as long as it’s modified for pregnancy.” She says 30 minutes a day, five days a week, is ideal. “I recommend that my moms get both cardio and strength exercises.” She says there are many exercise routines specifically designed for pregnancy—pregnancy Pilates, pregnancy yoga, and pregnancy Zumba are just a few.

With a few minor changes, guidelines for healthful eating during pregnancy basically are the same as they are for the general population. However, pregnant clients should know that eating healthfully during those nine months, and the time leading up to pregnancy, are more important than ever. They really are eating for two, but in quality, not quantity.

— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Texas.


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