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Pregnant women face a dilemma. Some need to gain weight (but not too much) while others should gain little, if any, during a time when the world seems to be urging them to eat for two. It’s no wonder they have trouble meeting the goals for weight gain during pregnancy recommended by what is now the National Academy of Medicine.

A study of more than 1.3 million pregnant women, published last week in the Journal of the American Medical Association, showed that 47 percent of them gained more weight than recommended by the guidelines.


That’s a problem because women whose weight strayed outside of the guidelines were more likely to have experienced complications during their pregnancies. Those who gained too much weight were at increased risk for having caesarean sections and delivering babies with higher-than-average weights, sometimes known as macrosomia. Women who didn’t gain enough weight were at risk of having underweight babies.

We know from clinical research that women who gain too much weight in pregnancy have higher rates of gestational diabetes and complications from high blood pressure (pre-eclampsia); they also have more trouble losing weight after delivery, further contributing to the obesity epidemic. Excess weight gain during pregnancy also puts the developing baby at risk of obesity.

How do we help pregnant women stay within the weight-gain guidelines? Over the past two decades, numerous randomized trials have tested strategies like exercise, diet, and counseling to see if they can help pregnant women minimize weight gain. Even with such intensive interventions, nearly half of pregnant women still exceed weight-gain guidelines.


As I wrote in an editorial about the JAMA report, what motivates pregnant women the most tends to be the health of their baby. A study of women who were advised to quit smoking, for example, showed that 43 percent of pregnant women quit smoking because of the possible effects on their babies, whereas only 10 to 15 percent of non-pregnant women quit.

Many studies have shown that people may not successfully make a positive behavior change on their own, but may do so if they have someone they are accountable to, such as a study partner or a personal coach. In the case of pregnant women, knowing they are accountable to their growing baby can be an incredibly strong motivator.

Behavioral economics shows us that not losing something can be a stronger motivator than the promise of gaining something. One study, for example, showed that giving a financial reward up front for exercising then taking the money back if exercise goals aren’t achieved led to more people meeting their exercise goals than giving a standard reward after hitting their goals.

Translating this strategy to weight gain during pregnancy is more complicated. While we shouldn’t use scare tactics, it’s important that pregnant women understand that some behaviors, like smoking and gaining too much or too little weight, can affect their babies’ health.

Pregnant women overwhelmingly want to do the right thing for themselves and their babies. But eating healthfully to gain just the right amount of weight isn’t easy, especially when a woman is also juggling a job and possibly caring for a family. It’s made even harder by all the people urging them to eat for two when most should be eating only an extra 100 calories or so a day.

One strategy may be to surround them with messages that are delivered persistently and frequently, perhaps through social media and through public health campaigns. This approach to smoking and drinking alcohol in pregnancy has led to significant changes in behavior.

While the negative health effects of excessive weight gain are experienced over many years and significantly downstream in most individuals, they happen more rapidly in pregnant women. So we may be able to use these more immediate effects to help this receptive population better follow weight-gain guidelines. That could also influence the overall obesity epidemic. If we don’t find better ways to fight obesity, we will see an increasing number of complications — not just in pregnant women and their babies, but in our entire population.

If we can learn to harness the psychology behind what motivates pregnant women to make better choices for the health of their babies, we will not only improve outcomes of pregnancy but may also find better ways to fight the obesity epidemic on a global scale.

Aaron B. Caughey, MD, is chair and professor of obstetrics and gynecology and associate dean for women’s health research and policy at the OHSU School of Medicine in Portland, Ore.

  • Hi, great article, I thought I may have something to add. I don’t think weight gain is entirely psychological, there might be a physiologic change happening as well.

    Normally I am incredibly athletic, I eat mostly unprocessed organic food, and care about being healthy. Maintaining my weight is no issue whatsoever when I am not pregnant, it’s almost instinctive, I never have to watch what I eat or measure food.

    Pregnant however, pregnant I feel starving all the time, ravenous every few hours. During each pregnancy the sensation of fullness that signals the end of eating just wasn’t there. It’s uncomfortable feeling that insatiably hungry all the time. So the cure is obviously to eat more. Even using mostly healthy foods it was impossible to stop the excess weight gain.

    I’m wondering if looking into the effects of pregnancy hormones on hunger signaling hormones like leptin and ghrelin might give insight into this problem also? It makes sense from an evolutionary perspective. During most of human history food was scarce, so it benefitted pregnant women to seek as much food as possible for the baby’s sake. We may have evolved an adaptation that causes excess eating that no longer serves us in the era of abundant food.

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