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What it means if you lose weight during pregnancy — and when to worry

What causes a pregnant woman to lose weight?

Doctor talking to a pregnant patient
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Weight gain is a very real and very normal part of pregnancy. Every person expects to gain while during their pregnancy, but sometimes they may notice the scale going down instead of up. Pregnancy requires extra calories and extra nutrition to feed a growing baby, which is why it can be very concerning when a pregnant person notices they are losing weight.

Weight loss during pregnancy may be more common than you think and isn’t necessarily cause for alarm unless it’s a consistent pattern throughout the pregnancy and not just a short-lived dip on the scale. There are many factors that can cause a pregnant person to lose weight, but that doesn’t mean it can’t be concerning when it happens. You should always consult your doctor if you’re concerned about your weight gain or loss during pregnancy, but if you’ve found yourself asking, “Why am I losing weight while pregnant?” here are a few possible explanations.

pregnant woman standing on scale
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It’s not uncommon

Believe it or not, losing weight during pregnancy isn’t uncommon, especially during the first trimester. Morning sickness can be one of the biggest causes of weight loss during the first trimester when some women are simply too nauseous to eat or are vomiting frequently. Pregnancy can also inspire a healthier lifestyle, which can also result in some early-stage weight loss, especially if a woman begins a moderate exercise program and really focuses on their nutrition compared to their pre-pregnancy lifestyle. Typically, as Very Well Family notes, losing weight during the first trimester usually isn’t anything to worry about, especially if it’s followed by the recommended weight gain.

pregnant woman looking at scale
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When should I worry about weight loss during pregnancy?

Although losing a bit of weight early in your pregnancy may not be something to worry about, there are times when it can be cause for alarm. Severe morning sickness, clinically known as hyperemesis gravidarum, can cause harm to both the mother and the baby if not treated. According to BabyCenter, hyperemesis gravidarum is characterized by “persistent nausea, vomiting several times a day, weight loss, dehydration, reduced appetite, and fainting.” This can cause not only weight loss in the expectant mother but also harm to the baby. If you feel you’re losing weight because of severe morning sickness, you should speak to your doctor immediately because you may require medical intervention.

Kimberly Henderson, DO, an ob-gyn at Health Quest Medical Practice told The Bump that pregnancy weight loss is “only a cause for concern if pregnancy weight loss hits 5 and 10 percent of a woman’s total body weight.” Pooja Shah, MD, an ob-gyn and regional medical director for Banner Medical Group AZ East explained to the website that weight loss during the third trimester could be a problem and should be brought to the attention of your doctor.

Although it may be due to simple fluctuations, it could also be related to low amniotic fluid or pregnancy-induced hypertension or preeclampsia. Since babies see their most growth during the third trimester, most women also see an increase in their weight gain during that time. If you’re losing weight in your third trimester, don’t ignore it and speak to your medical provider. You should also contact your doctor if you are experiencing any sudden, dramatic weight loss at any time.

Female doctor touching pregnant woman's stomach, smiling
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Why did I get skinny while pregnant?

Weight gain is a part of pregnancy, so while some weight loss may be normal and no cause for concern, it shouldn’t be the goal either. That being said, some women do find a renewed commitment to their health once they find out they are pregnant and this healthier lifestyle can definitely lead to some initial weight loss. Women who are heavier before getting pregnant or have a BMI over 30 may also tend to lose a bit of weight at the beginning of their pregnancy, which may even be beneficial.

Pregnant woman at doctor's office looking at an ultrasound
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Causes of weight loss during pregnancy

As we mentioned above, morning sickness, a healthier lifestyle, and typical weight fluctuations can cause first-trimester weight loss, but any sudden weight loss should be brought to the attention of your doctor. Very Well Family notes some other potential causes for weight loss during pregnancy, including:

  • Autoimmune disorders
  • Cancers
  • Eating disorders
  • Endocrine imbalance
  • Gastrointestinal diseases
  • Infections
  • Neurologic abnormalities
  • Psychiatric disorders
  • Substance use
  • Uncontrolled overactive thyroid
  • Undiagnosed diabetes
  • Other chronic diseases

“The most important intervention for a woman who is losing weight in pregnancy is to identify and treat the underlying reason for the inadequate weight gain,” explained Dr. Chris Han, a physician at the Center for Fetal Medicine and Women’s Ultrasound. While some weight loss early in the pregnancy is normal, Dr. Han also noted that “losing weight during pregnancy has been associated with increased risk of decreased birth weight and preterm delivery.”

Fruits in a bowl and on a table with muffins
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What to do if you’re losing weight

If you find yourself struggling to gain the recommended weight during pregnancy Peanut suggests, ensuring you’re eating a balanced diet full of nutrient-rich foods while limiting sugary snacks. Make sure you’re staying hydrated by drinking enough water, reducing caffeinated beverages, and keeping active with light exercise.

Pregnant person holding plate of healthy dinner over their bare bump
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How much weight should you gain during pregnancy?

Every person is different, which is why knowing how much weight you should gain during pregnancy isn’t the same for everyone. The American College of Obstetricians and Gynecologists (ACOG) advises that most people will see the smallest weight gain in the first trimester, while individuals may gain anywhere between a half pound and a pound per week in the second and third trimesters. This is typical for those who are a healthy weight prior to getting pregnant.

For most, you don’t need any additional calories during the first trimester, which is why many will see weight loss, especially if they experience any morning sickness. In the second trimester, those who were a healthy weight before pregnancy will need approximately 340 extra calories a day, while the third trimester will require about an extra 450 calories a day.

Every woman’s pregnancy is different, but if you’ve noticed a drastic weight loss or you’re struggling to gain the recommended weight, reach out to your doctor for professional advice.

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Kelli Catana
Kelli is a freelance writer who has covered the world of entertainment, pop culture, parenting, and lifestyle for various…
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