Mar 31, 2023 • 10 min read

Can I Lose Weight While Pregnant?

Medically Reviewed by Kim Langdon, MD on 3/31/2023
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Andrea was excited to see the “plus sign” on the home pregnancy test, but she had just started a diet and had already lost eight pounds. She wanted to lose 25 pounds by the end of the year and wondered if she could continue her weight loss journey while pregnant.

Andrea is among many women who find they are pregnant while dieting. Others may decide that pregnancy would offer a great chance to lose weight, believing that the baby will simply “steal” what it needs to grow. And then some women suffer from persistent nausea or have health issues that result in unintended weight loss.

But is it safe to lose weight while pregnant?

The short answer is no. Dieting to lose weight is unsafe in pregnancy, even if you become pregnant when you are already overweight.

This guide will go over the risks of weight loss during pregnancy and describe ways to safely gain the weight you need to during your pregnancy. Safe and healthy weight gain in the months you are pregnant is not only beneficial to you; it is essential for your baby’s optimal growth and development.

Why it’s generally not safe to lose weight while pregnant

At the moment you become pregnant, your baby begins its 268-day in-utero journey, starting as a single cell and becoming a highly developed human weighing six to ten pounds.

While the baby’s placenta is generally efficient at gaining the necessary nutrients to grow, it’s still essential for those nutrients to be consumed by the pregnant mom-to-be.

What are the known risks of losing weight during pregnancy?

  • Low infant birth weight. Babies who do not get enough calories in utero will not be able to grow adequately. Part of the problem is that the placenta does not develop enough size to provide the nutrients the baby needs, particularly in the second and third trimesters.
  • Preterm birth. If the baby is undernourished in the womb, the placenta can give off signals that trigger early labor. A baby born prematurely can have complications that may last a lifetime.
  • Delivery complications. There is a slightly increased risk of needing to have an episiotomy and stitches when you give birth to your baby.
  • Stillbirth. A fetus may not receive an adequate supply of oxygen if the placenta has failed to develop properly. The baby can be stillborn after having too little oxygen or other nutrients.  
  • Infant death. For unknown reasons, a baby born after its mother has failed to gain an adequate amount of weight during pregnancy has a higher risk of death shortly after birth and up to a year of age.

Studies show that the timing of your weight gain also matters during pregnancy. Low pregnancy weight gain during the first trimester is less injurious to your baby than failing to gain weight later on.

This is good news for women who may have morning sickness or other factors causing first-trimester weight loss. We’ll cover the reasons for first-trimester weight loss next.

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Why some women lose weight in early pregnancy

Weight loss is not uncommon in the first trimester. Many women experience nausea after eating early in pregnancy. Additional problems like heartburn and acid reflux during pregnancy can reduce appetite or restrict the types of foods a pregnant woman can eat. You can learn more about the causes of appetite during pregnancy here.

A more severe condition called hyperemesis gravidarum causes excessive amounts of vomiting during pregnancy. It can lead to fluid and electrolyte disturbances in your body, dehydration, and low food intake. If you develop this uncommon problem, you should be in regular contact with your healthcare provider to help you navigate your nutritional needs.

Another reason you might lose weight in the first trimester is that you are active and haven’t yet reduced your workout routines. Exercise is generally not restricted in the first trimester unless you have a risk of injury while exercising. As your food intake does not need to be altered during this time, you may lose a few pounds naturally.

You might also not realize you’re pregnant right away and may lose weight from a preexisting diet. If this is the case for you, it’s time to stop dieting and begin to eat the recommended amount of calories for your stage of pregnancy.

This type of first-trimester weight loss is not dangerous to your baby. However, it is not recommended that you intentionally lose weight at any time during your pregnancy.

How much weight you should gain during pregnancy

The amount of weight you should gain during your pregnancy depends on your pre-pregnancy weight. If you are underweight, you should gain more weight during your pregnancy than if you are overweight.

Here’s how to determine your ideal pregnancy weight gain:

Step 1: Determine your Body Mass Index (BMI)

Your BMI can help you understand your ideal weight as well as the weight you are as measured against your height. The BMI accounts for the fact that taller individuals naturally have a higher weight than shorter people.

The calculation for BMI = (weight in pounds * 703) / (height in inches)^2

You can also use an online BMI calculator to find this value.

Step 2: Find your ideal weight gain

Once you know your BMI, use this value to see how much weight you need to gain:

Step 3: Monitor your weight & adjust your diet accordingly

Now that you know how much weight you should gain during pregnancy, you should regularly weigh yourself to monitor your progress. Try to weigh yourself at the same time each day to get a more consistent understanding of changes.

It’s also important to listen to your body, not just the scale.

“We get so many messages about women’s health and weight,” says Natasha Eziquiel-Shriro, RDN, one of Zaya Care’s Dietitians. “Once pregnant, your focus should be on eating habits for nutrition and stamina, daily movement that relieves tension and improves fitness, and if needed, finding a few new ways to cope with stress. This goes for all pregnancies.”  

If you’re feeling like you have no energy or are dealing with other issues that aren’t expected during a healthy pregnancy, it may be related to your diet. In this case, you may want to consider working with a nutritionist.

Here at Zaya Care, we can match you with a pregnancy nutritionist that can help you make sure you’re eating healthily and gaining the ideal amount of weight during pregnancy.

>> Learn more: Gaining weight during pregnancy but not eating a lot

Can I diet while pregnant?

Dieting while pregnant comes with a number of risks, including:

  • Dehydration. If you are restricting your calories, you may drink too little as well. Adequate fluid intake is important to your baby’s water balance. Remember that fluid is what your baby is living in throughout your pregnancy.
  • Low nutrient intake. Dieting can mean you are not getting the minerals and vitamins your baby needs to grow and develop. Protein intake during pregnancy is also critical to your baby’s ability to make the cell’s building blocks, hemoglobin, and essential enzymes.
  • Unbalanced nutrient intake. Depending on the diet, you may end up with an imbalance in your nutrient intake that can affect your baby. Detoxing and trendy diets like intermittent fasting during pregnancy may deprive you and your baby of the specific nutrients you need.
  • Low energy uptake. When we talk about “energy” in terms of health, we mean “calories.” If you don’t take in enough calories, the energy you need for everyday activities and muscle use will be insufficient. Your baby will also feel the pinch in your daily energy intake.

Ideally, your goal should be to eat healthily throughout pregnancy. Avoid crash diets and very restrictive diets such as keto during pregnancy.

Healthy, well-balanced meals with plenty of fluids and no alcohol can help you feel your best. Eating ideal foods for pregnancy like fruits, veggies, whole grains, and lean meats along with whatever supplements your provider recommends can ensure your baby has optimal nutrition.

If you feel confused or feel like you aren’t gaining enough weight, you may want to consult with a prenatal nutritionist. Your nutritionist can examine your current eating habits and help you make a plan to gain the optimal amount of weight for your baby’s health and well-being.

If you’re interested in working with a prenatal nutritionist, you can use our search tool to find providers that accept your insurance.

>> Learn more: Symptoms of not eating enough during pregnancy

Risks of being overweight while pregnant

While dieting is not recommended, you should be aware of the potential for complications if you are overweight when you become pregnant—or if you gain too much weight during your pregnancy.

Being overweight in pregnancy can cause a variety of health and pregnancy complications:

  • Gestational diabetes. Being pregnant triggers the natural tendency toward insulin resistance, which is the issue that causes type 2 diabetes. Obesity creates an environment more likely to cause high blood sugar during pregnancy. Gestational diabetes resolves after delivery but carries the risk of several pregnancy and fetal complications.
  • Preeclampsia. Preeclampsia is a disease of the latter half of pregnancy in which your blood pressure is high, and you begin to leak protein into your urine. The disease triggers many different effects in your body that can lead to seizures, liver failure, stillbirth, and other health issues for you and your baby.
  • Gestational hypertension. Gestational hypertension is essentially “high blood pressure during pregnancy.” While this is less severe than preeclampsia, high blood pressure can still cause the placenta to be unable to adequately nourish your baby or provide enough oxygen. You can learn more about necessary diet changes for high blood pressure during pregnancy here.
  • Obstructive sleep apnea. When a person is overweight, the extra thickness in their neck and throat can cause them to lack oxygen during sleep. Sleep apnea is more than snoring and may mean that you and your baby aren’t getting the oxygen you need.
  • Cesarean delivery. Extra weight also causes an excess thickness of the pelvic tissues and means that the birth canal is narrower. If your baby is larger than it should be (a common issue in women who gain too much weight during pregnancy), this adds to the chance that a vaginal birth will not be successful.
  • Infant birth injuries. If you do have a successful vaginal delivery, you could require forceps or vacuum devices to facilitate the birth. Your baby can be injured by these devices or can have injuries from becoming trapped in the birth canal.

If you have concerns about your weight or feel you might be at risk for complications because you are overweight, make sure to bring it up with your healthcare provider.  

>> Find a prenatal nutritionist that accepts your insurance & can help you eat healthily during pregnancy

How to make sure you’re not gaining too much weight during pregnancy

If you are worried about gaining too much weight during your pregnancy, begin thinking about how to manage your dietary habits early in the first trimester.

Managing your weight during pregnancy is NOT dieting. Instead of restricting food intake or eating “diet” foods, you begin to eat healthily and manage your weight gain using these helpful tips:

  1. Know how much weight you must ideally gain. Calculate your BMI and determine your optimal weight gain. Weight gain is little to none in the first few weeks of pregnancy, but in the second and third trimesters, your weight gain should be steady. 
  2. Gain energy from the right foods in the right amounts. Become a calorie counter and know the calories in the foods you eat. Be aware of portion sizes and keep your portion sizes within the right range. For example, a portion of meat is just three to four ounces, and your toast in the morning is one piece per portion.
  3. Exercise regularly. If you have just 30 minutes a day and use that time to go on a brisk walk, swim, or bike ride, you will stay fit all the way through your pregnancy. If you participate in any other noncontact sport, you can continue your participation as long as you feel well.
  4. Obtain a scale and monitor your weight. A simple bathroom scale can help you know you’re on track, gaining weight slowly and steadily.
  5. Get regular prenatal checkups. Your healthcare provider will help you if you need advice or are concerned about your health or the health of your baby.
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When it’s safe to lose weight after giving birth

“I’d say it’s best to hold off on major weight loss plans until after the fourth trimester,” says Natasha Eziquiel-Shriro, RDN, one of Zaya Care’s Dietitians. “In terms of exercise, the body needs at least 6 weeks to heal after giving birth, longer depending on your health before pregnancy or labor experience.”

Breastfeeding may offer a chance to lose weight naturally. Research says that breastfeeding moms lose weight slightly more than those who aren’t breastfeeding. To give your baby enough nutrients, you must take in at least 1800 calories per day.

Eziquiel-Shriro reminds, “Stay hydrated and eat nourishing foods throughout the day.” Intense exercise or a restrictive diet can be shocking to the system, so much so that the stress can reduce milk supply.

“Even if not breastfeeding, you might need the energy from an extra small meal or snack more than you think,” adds Eziquiel-Shriro. Replenishing your body after childbirth at the same time as caring for an infant, she says, “is no small feat!”

How a prenatal or postpartum nutritionist can help

There are both prenatal nutritionists and postpartum nutritionists who can be very helpful with issues around weight gain or loss during pregnancy and beyond. Most nutritionists who specialize in this field can handle both stages, so you don’t need to change practitioners after delivery.

A prenatal nutritionist can help by evaluating your diet as soon as you know you’re pregnant. They can calculate your total and weekly weight gain and help you figure out meal planning and shopping for food.

After delivery, your nutritional needs will change. Your nutritionist can assist you with weight loss after pregnancy, whether you are breastfeeding or not. Your goals will be matched with recipes, shopping lists, tips, and advice.

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Christine Traxler MD is a family physician, lifelong writer, and author with a special interest in mental health, women’s healthcare, and the physical after-effects of psychological trauma. As a contributing writer and editor for numerous organizations, she brings a holistic focus to her work that emphasizes healing and wellness through daily self-care, connecting with others, and setting stepwise goals toward achieving more balanced and authentic lives.