What to Do About Weight Loss During Pregnancy

Common Reasons, Concerns, and Special Considerations

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Losing weight in pregnancy might seem alarming but it's fairly common. Sometimes, it is nothing to worry about, especially if the weight loss is short-lived, followed by the expected weight gain. However, losing weight is cause for concern if the weight loss is substantial and/or long-lasting or occurs after the first trimester.

In those cases, losing weight can be problematic and will need medical attention. Physicians track your weight gain or loss at every prenatal check-up for this very reason.

Below, we explore why pregnancy weight loss occurs, when to be concerned, and what do about it.


In early pregnancy, the baby is still quite tiny and only has minimal caloric and nutritional needs. So, a bit of unintentional weight loss in this period (usually related to morning sickness) won't negatively impact your baby's development.

Keep in mind, too, that healthy weight gain in the first trimester would only be a few pounds—usually 2 to 4 pounds. If you lose a couple of pounds, rather than gain any, the net loss will only be several pounds. These pounds will usually be quickly recouped when nausea fades and the appetite returns by the second trimester.

Why Weight Gain Matters

After the first trimester, however, gradual weight gain becomes vital for the health of the baby as well as for building up essential fat stores to prepare a women's body for supporting a growing baby, labor, delivery, and breastfeeding.

Also, it's never wise to follow a strict diet or drastically cut calories or food groups while expecting. Your growing baby's optimal development will increasingly rely on you consuming adequate calories and nutrients. However, to some extent, your baby is able to use your body's fat stores if needed.

Pregnancy can trigger morning sickness as well as encourage women to shift to healthier eating styles, both of which can result in early pregnancy weight loss. In some cases, a small amount of doctor-supervised weight loss may also be recommended for pregnant women who have a Body Mass Index (BMI) of obese or greater.

BMI Explained

Body Mass Index is a guideline based on your height and weight and is an estimate of your body fat. Be aware that healthy weights are more than simply your BMI calculation and many women (over 50%) fall outside of the "normal" category. Consult with your doctor to determine if your weight is healthy for you.

Morning Sickness

Morning sickness is very common, impacting about 70% to 80% of pregnancies in the first trimester. Caused by the huge hormonal shifts of pregnancy, morning sickness symptoms include:

  • Reduction in appetite
  • Vomiting
  • Sensitivity to smells
  • Fatigue
  • Nausea

So, many pregnant women have trouble keeping food down, which is why some weight loss may occur. But as long as you are still eating a little and not losing more than a few pounds, mild to moderate or occasional morning sickness is not something to be concerned about. Usually, these symptoms improve by week 14 and weight gain will commence.

Hyperemesis Gravidarum

However, sometimes morning sickness can escalate to a more serious extreme morning sickness known as hyperemesis gravidarum (HG). In this condition, women experience magnified symptoms and more substantial weight loss.

Dr. Chris Han, a physician at the Center for Fetal Medicine and Women's Ultrasound, says, "A patient is felt to have HG if she has persistent vomiting accompanied by weight loss exceeding 5% of the pre-pregnancy body weight, along with evidence of ketones in their urine."

For example, a woman with HG who starts out her pregnancy weighing 140 pounds would lose about 7 pounds or more.

Research shows that about 36,000 women are hospitalized each year in the United States with cases of HG. The actual number of women with the condition might be much higher since women may be treated at home or as outpatients through their health care provider.

Hyperemesis gravidarum is characterized by severe nausea and vomiting, which can result in severe dehydration and inability to keep food down. Thus, there is a potential to lose weight if you experience this condition.

HG usually appears in weeks 4 to 6 of pregnancy and can peak around 9 to 13 weeks. Most women receive relief around weeks 14 to 20, however, some women require care throughout their entire pregnancy. Hyperemesis can be treated outside the hospital, but in severe cases, hospitalization may be necessary.

Treatment Options

There is no way to prevent this condition, but there are many ways to treat it. Medical interventions may include medications, as well as infusions of intravenous fluids to replace lost fluid and electrolytes.

In extreme cases, nutritional support is necessary and may require a surgical procedure. Additionally, some alternative therapies may be recommended. Some examples of these are bed rest, herbal treatments, and acupressure.

Other Causes

If morning sickness is not to blame, unintentional weight loss, especially sudden weight loss, is a concern and should be evaluated by a medical doctor as soon as possible. Likewise, weight loss due to changes in diet, eating disorders, food insecurity, and intentional dieting are not safe and should be discussed with your care provider.

Some other causes of weight loss during pregnancy include:

  • Cancers
  • Uncontrolled overactive thyroid
  • Undiagnosed diabetes
  • Gastrointestinal diseases
  • Psychiatric disorders
  • Endocrine imbalance
  • Neurologic abnormalities
  • Infections
  • Substance abuse
  • Autoimmune disorders
  • Eating disorders
  • 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," says Dr. Han.

When Weight Loss Is Advised

Unless recommended by your physician, intentional weight loss is not recommended during pregnancy. In some cases, minimal weight loss is advised for some women who have extreme obesity. However, this is somewhat controversial as research and experts are divided about the benefits and risks of this approach.

"Some studies have shown that weight gain below the recommended limits may provide some benefit for women with higher body mass index (BMI) > 30 kg/m2 before pregnancy, but may increase the risk for small babies in women with normal or low BMI," explains Dr. Han.

Modest weight loss for women who have obesity has been shown to lower the risk of:

  • Preeclampsia
  • Gestational diabetes
  • Emergency c-section
  • Having an overly large baby

However, those benefits may come with a cost (except for women with a BMI over 35) as gaining below the recommended guidelines also increases the risk of complications for your baby.  In cases where a woman is in the highest BMI classification, she may have enough stored fat to safely sustain her baby without gaining as much weight.

Your doctor will be the best person to evaluate whether or not weight loss or minimizing weight gain would be appropriate in your specific case.

Typical Weight Gain Recommendations

The current recommendations from the National Academy of Medicine are to target total weight gain to guidelines based on your pre-pregnancy body mass index:

  • BMI <18.5 kg/m2 (underweight) should aim for 28 to 40 pounds
  • BMI 18.5-24.9 kg/m2 (normal) should aim for 25 to 35 pounds
  • BMI 25-29.9 kg/m2 (overweight) should aim for 15 to 25 pounds
  • BMI 30-34.9 kg/m2 (obese) should aim for 11 to 20 pounds
  • BMI > 35 kg/m2 (extremely obese) should aim for 11 to 20 pounds unless advised to gain less by their doctor

These optimal weight gain numbers are increased for those carrying twins or other sets of multiples.

Possible Dangers

Losing a few pounds is usually okay at the beginning of pregnancy. However, overall, "losing weight during pregnancy has been associated with increased risk of decreased birth weight and preterm delivery," says Han.

According to the Centers for Disease Control and Prevention, preterm birth occurs when a baby is born too early, which is defined as before 37 weeks of pregnancy have been completed. Babies who have low body weight at birth and are pre-term may be susceptible to other health conditions or abnormalities because their bodies have not had the ability to develop fully.

Your physician will monitor your weight closely and you will be weighed at each prenatal appointment in order to prevent complications that could impact your baby, such as:

  • Pre-term birth
  • Small size and/or low weight at birth
  • Large size and/or high weight at birth
  • Developing obesity later in life

How to Gain Enough Weight

Eating small, frequent nutrient-dense meals can help you meet your caloric needs (even when you feel nauseous) and prevent weight loss. When you are not feeling well it can be difficult to meal prep and plan on your own. If that's an issue for you, ask a partner, friend, or family member to help prepare or provide your meals.

If you continue to have difficulty and are unable to gain enough weight or you continue to lose weight, consider working with a dietitian. A dietitian can provide individualized meal plans based on your nutrient and calorie needs and preferences.

In addition, it can be helpful to treat any symptoms that are interfering with eating. Treatments might include taking anti-nausea, anti-depression, or anti-thyroid medications, depending on your particular case.

Dr. Han also suggests skipping at-home weigh-ins, which can be inaccurate and stressful. "Monitoring weight gain trajectory at routine prenatal visits is important, although I never recommend weighing daily at home, due to normal day-to-day fluctuations," she says.

Nutritional Needs

Most women need to increase their calorie intake by about 340 to 450 calories per day in the second and third trimesters for adequate weight gain and nutrition.

Aim to eat a mix of lean proteins (such as meats, nuts, seeds, legumes, eggs, dairy, cheese, and tofu), carbohydrates (in the form of healthy fruits, vegetables, and whole grains), and a healthy amount of fat. Also, drink plenty of water, which can be especially helpful for reducing nausea.

Understanding portions and nutritional needs can be complex and many women, particularly those with other medical needs, may benefit from seeing a dietitian who can assist them in this process. Dr. Han says, "Nutritional recommendations should always be individualized and take into consideration, physical activity, age, weight, and health conditions."

A Word From Verywell

Weight loss during early pregnancy can be common, but in general, is not recommended. Aside from regular morning sickness, unintentional weight loss, and inability to gain weight require a medical evaluation.

If your weight loss is being caused by an underlying condition, your physician can treat it to prevent future weight loss and protect your health and that of your baby. Evaluation by a dietitian can help with nutritional guidance and individualized meal planning. Most importantly, focus on healthy, nutritious eating (and enough of it) rather than the number on the scale.

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Article Sources
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