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Why You May Be Losing Weight While Pregnant

Weight loss during pregnancy can be concerning, but there are many possible reasons for it—and many often simple solutions. We asked experts for the lowdown.
ByMaggie Overfelt|Updated March 6, 2020
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pregnant woman weighing herself on scale at home
Image: gpointstudio | Shutterstock

Soon-to-be moms and their doctors talk a lot about pregnancy weight gain. After all, the Centers for Disease Control generally advises women to put on a total of 25 to 35 pounds during pregnancy, depending on their BMI. But what if you’re losing weight while pregnant? It can happen. Depending on when it occurs, pregnancy weight loss could be perfectly normal or possibly concerning. Read on to find out the possible causes of weight loss during pregnancy, how you and baby can get the nutrients you both need, and when to call your doctor for help.

Can You Lose Weight While Pregnant?

Generally speaking, no mom-to-be should intentionally try to lose weight once she knows she’s pregnant, even if she’s overweight. Research shows that losing weight on purpose during pregnancy can increase the risk of complications for baby. Further, restricting calories and nutrients can be harmful to you and your developing child, says Pooja Shah, MD, an ob-gyn in Chandler, Arizona.

If you are obese, your doctor will offer you advice on how to avoid possible complications. “For weight gain during pregnancy, we base our recommendations on what mom’s pre-pregnancy BMI is,” says Kimberly Henderson, DO, an ob-gyn at Nuvance Health Northern Dutchess Hospital in Rhinebeck, New York. “Women who are very obese—a BMI of over 40—may not gain any weight in their pregnancy.”

Still, it’s possible for you to find yourself losing weight while pregnant, even if it’s not intentional. Read on to learn what might be causing you to drop those pounds and what you should do about it.

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Weight Loss in the First Trimester

Doctors note that most women gain only between 1 and 5 pounds in the first three months of pregnancy, so if you’re experiencing weight loss in your first trimester, chances are, it’s nothing to worry about. “It’s not uncommon for women in their first trimester to lose a little bit of weight due to bad nausea and vomiting that precludes them from eating in a normal way,” says Henderson. A loss of appetite because of the morning sickness is a common cause of pregnancy weight loss too. According to Henderson, it’s only a cause for concern if pregnancy weight loss hits 5 to 10 percent of a woman’s total body weight.

Weight loss during pregnancy could also happen if you’ve begun exercising daily and making a point of eating healthier foods for you and baby. If that’s the case you might need a few extra calories throughout the day to support your quickly-growing baby.

In very rare cases, pregnancy weight loss that’s progressive and/or excessive might be a sign of hyperemesis gravidarum, a complication characterized by severe morning sickness. This means throwing up more than five times a day, severe stomach pain and/or signs of dehydration. You might also not be peeing much, your urine is dark and you feel weak or dizzy. If you experience any of these symptoms or if you simply can’t keep anything down, call your doctor or midwife. “You should feel comfortable having an open conversation with your ob-gyn about weight gain goals in pregnancy, visit-to-visit weight changes, and any worrisome weight gain or loss,” says Shah.

Weight Loss in Late Pregnancy

Weight loss in the third trimester could be especially disconcerting. Losing weight while pregnant at this late stage could be related to poor baby growth, low amniotic fluid or pregnancy-induced hypertension or preeclampsia. If you’re losing weight and it’s beyond your first trimester, call your provider. It could very well be something harmless—such as fluctuations in day-to-day water retention—says Shah. But to be safe, it’s always best to consult with your doctor.

What to Do If You’re Losing Weight While Pregnant

By all means, talk to your doctor if you’re experiencing weight loss during pregnancy, if you feel dizzy or weak or if you can’t find relief for your nausea or vomiting. This is important at any time during your pregnancy, but it’s especially crucial in the second or third trimester. Your doctor or midwife will work on zeroing in on the cause (including perhaps doing some lab tests) and then recommending the best course of action based on their findings. In the case of nausea, the antidote may be as simple as an over-the-counter supplement, such as vitamin B6, or a prescription-strength medication. Oftentimes, IV fluids can help with dizziness and weakness.

Beyond that, says Henderson, eating thoughtfully is key to avoid losing weight while pregnant. Keep these strategies in mind:

  • Eat smaller meals and space them out
  • Avoid foods and smells that gross you out
  • Eat a little something—like a cracker—immediately after you wake up in the morning
  • Take your prenatal vitamin faithfully
  • Add about 300 extra calories a day (no need to double what you eat!); the easiest way to accomplish this is with healthy snacks between meals
  • Stay hydrated
Sources

Kimberly Henderson, DO, is an ob-gyn at Nuvance Health Northern Dutchess Hospital in Rhinebeck, New York. She graduated from medical school at Chicago College of Osteopathic Medicine-Midwestern University in 2011.

Pooja Shah, MD, is an ob-gyn in Chandler, Arizona. She received her medical degree from the University of Illinois College of Medicine at Chicago.

Centers for Disease Control and Prevention, Weight Gain During Pregnancy, June 2022

PLOS One, Weight Loss Instead of Weight Gain within the Guidelines in Obese Women during Pregnancy: A Systematic Review and Meta-Analyses of Maternal and Infant Outcomes, July 2015

The American College of Obstetricians and Gynecologists, How Much Weight Should I Gain During Pregnancy?, August 2021

National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases, Understanding Calorie Burning in Early Pregnancy—Moving Toward Improving Health for Mothers and Children, June 2018

National Library of Medicine MedlinePlus, Prenatal Care in Your Third Trimester, April 2022

American Pregnancy Association, Natural Sources of Vitamin B During Pregnancy

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