Being Medically Overweight During Pregnancy Can Raise Your Risk For Birth Complications

Kristin Canning
·8 min read

From Women's Health

When you picture getting pregnant, you might think of that time as a period when you should gain weight with abandon (after all, that's how a lot of TV shows and movies position pregnancy). But weight gain during pregnancy is actually pretty complicated—and can be even more complex if you were medically considered overweight or obese when you became pregnant.

Here, ob-gyns help clarify all of the complicated questions surrounding the topic of being medically overweight and pregnant—and what you can do to have the healthiest and safest pregnancy possible.

First of all, what qualifies as being medically overweight or obese?

These categories are based off of BMI (Body Mass Index), which is a measurement of your weight in comparison to your height and is often used as a health measure in health care settings. If you have a BMI of 25 to less than 30, you're considered overweight by medical measures. If your BMI is 30 or higher, you're considered obese. (You can find a BMI calculator here.)

Using BMI to determine someone's health based on weight is problematic (and pretty outdated), since it can't take into account your muscle mass and many other factors that impact wellness. But it is how many doctors still determine whether you're at a healthy weight at the start of your pregnancy and throughout, so for the sake of convenience, it's what we'll reference throughout this article. But know that it's best to consult your doctor about your weight, other health markers, and lifestyle to get a more accurate view of your health and how your pregnancy will go.

How common is it to enter pregnancy overweight or obese?

It's super common. About 27 percent of U.S. women qualify as overweight and another 40.4 percent are considered obese, according to the National Institutes of Health (NIH). That means it's likely that many women enter pregnancy at a higher weight than recommended as well. (Though it's worth noting that being overweight or obese can affect your fertility and ability to get pregnant, too.)

Black women may be especially at risk of weight-related pregnancy complications, since four out of five Black women in the U.S. are considered overweight or obese, per the U.S. Department of Health and Human Services, Office of Minority Health. Black women also face a greater risk of maternal mortality due to several underlying factors.

How much weight do doctors recommend you gain during pregnancy?

This all depends on what weight you start your pregnancy at. Per the Centers for Disease Control and Prevention (CDC), these are the recommended amounts of weight you should gain:

  • If your BMI is less than 18.5, you should aim to gain 28-40 pounds

  • If your BMI is 18.5-24.9, you should aim to gain 25-35 pounds

  • If your BMI is 25-29.9, you should aim to gain 15-25 pounds

  • If your BMI is 30 or higher, you should aim to gain 11-20 pounds

About one-third of women gained the recommended amount of weight during pregnancy, according to the CDC, and most women gained weight outside the recommendations—21 percent gained too little, and 48 percent gained too much. Note that these amounts change if you're pregnant with multiples.

What are the health impacts for a mother who is overweight or obese while pregnant?

Being overweight or obese while pregnant can predispose you to certain risks, says Keri Peterson, MD and Women's Heath advisory board member. These include:

  • Gestational diabetes. This is diabetes that starts during pregnancy. Having this condition puts you at higher risk for a C-section, as well as having diabetes (and your child having diabetes) in the future.

  • Preeclampsia. This is a serious high blood pressure condition that occurs during pregnancy, and starts with gestational hypertension, note Dr. Peterson. It can lead to kidney and liver failure, as well as seizures and stroke. Preeclampsia may result in the need for an early delivery.

  • Sleep apnea. This condition causes you to stop breathing for small periods of time while you're asleep, essentially waking you up over and over at night, leading to fatigue.

Does the baby face any health risks if the mother is overweight or obese while pregnant?

There are also risks for the baby while the mother is overweight or obese during pregnancy. According to the American College of Obstetrics and Gynecologists (ACOG), these include:

  • Miscarriage. Obese and overweight mothers are more likely to experience pregnancy loss.

  • Preterm birth. The complications of being overweight or obese during pregnancy (like those listed above) can result in the need for a medically-induced preterm birth. This can lead to health problems for the baby later on, as they're not as developed when they're born.

  • Stillbirth. The likelihood of a stillbirth increases with BMI.

  • Birth defects. These include heart defects and neural tube defects.

  • Macrosomia. This is a condition in which a baby is born larger than is normal. This increases the chance of needing a C-section and ups the risk of the child being obese later in life.

The best way to avoid these health effects is to lose weight before you become pregnant. Even a small reduction in weight (5 to 7 percent of your current weight) can greatly lower your risk for pregnancy complications, per ACOG.

Should I lose weight while pregnant?

It depends. There are varying opinions on this, but "the long-standing advice has been to not lose weight when you’re pregnant—the growing fetus needs you to increase your fat stores because the baby needs the calories, and you’ll need to prepare for labor, delivery, and breastfeeding," says Kate White, MD, professor of obstetrics and gynecology at Boston University and Women's Health advisory board member. "However, there is some evidence that weight loss might be helpful for women with a BMI over 35 or 40—it may lower the risks of preeclampsia, gestational diabetes, emergency c-section, and macrosomia."

Still, losing weight during a pregnancy may also increase the risk of complications for the baby (including the baby not gaining enough weight and delivering preterm).

Basically, only you and your doctor can determine, based on your starting weight and health markers and health history, whether you should or should not aim to lose weight during your pregnancy and the safest way to do that. Your doctor can help you create an individualized plan that will ensure you have the healthiest pregnancy possible. Ideally, any weight gain or loss you experience during pregnancy will be gradual.

The best thing you can do to stay healthy during pregnancy is to start adopting healthy weight-based habits (like eating recommended portion sizes, eating filling, nutrient-dense foods, and regularly exercising) early on. Researchers found that when women got advice on how to maintain a healthy pregnancy weight between seven and 21 weeks, they were less likely to gain more than the recommended weight in the third trimester, per a study in the journal Obesity.

"It may be a better approach to try to avoid excessive weight gain, rather than actively try to lose weight, during pregnancy," says Dr. White. "But if you’re going to try to lose weight, you should do it in the first trimester—the weight you gain in the second and third trimesters is really needed by both you and the baby."

How can I maintain a healthy weight during pregnancy?

There's plenty you can do to make sure you maintain a healthy weight during pregnancy, and gain the recommended amount slowly. First and foremost, if you don't have a regular exercise routine, now is the perfect time to adopt one.

"It's important to exercise regularly when you're pregnant, which means 30 minutes a day of moderate intensity exercise," says Dr. Peterson. This could involve half an hour of fast walking, running, or swimming, or 30 minutes of weight lifting or a bodyweight HIIT workout. "All exercise is fine in the first trimester—as your belly grows, you will want to avoid things with a risk of falling, like skiing or cycling," says Dr. White, and certain exercises might be less comfortable. If you're new to exercise, ease into these workouts and listen to your body. If you're an avid exerciser already, you can likely maintain the level of intensity you did in your workouts before you were pregnant.

You also may want to talk to your ob-gyn or a nutritionist about the amount of calories you should be consuming on a regular basis. For weight loss, you'll need to consume less calories than your burn each day, and for weight maintenance, you'll want to consume around the same amount as you burn. "Don’t eat below 1,700 calories a day, even if you’re trying to lose weight," notes Dr. White. "And never try to lose weight in pregnancy without a doctor’s supervision."

Later in pregnancy, during the second and third trimesters, you'll need about 300 extra calories than normal per day to contribute to healthy pregnancy weight gain, according to ACOG. A dietitian can help you determine the healthiest foods you can eat to get those extra calories.

"Everyone should try to eat a healthy diet when they’re pregnant—especially one rich in folic acid, calcium and iron. And many pregnant people feel that eating small but frequent meals can help with nausea and helps them feel fuller throughout the day," says Dr. White.

The bottom line: Being overweight or obese during pregnancy can increase the risk of health problems for you and your baby. Talk to your doctor about the best way to maintain a healthy weight during pregnancy through your diet and exercise.

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