Can I Lose Weight During First Trimester? What Experts Advise

It’s a common question among expectant mothers: Can I Lose Weight During First Trimester? While generally, intentional weight loss isn’t recommended during pregnancy, the early weeks, particularly the first trimester, can sometimes be an exception. However, attempting to lose weight through dieting or severe restriction at any stage of pregnancy can mean missing out on crucial nutrients vital for both mother and baby.

Portrait of Dr. Cheryl Axelrod, an OB-GYN who medically reviewed pregnancy weight advice.

Medically reviewed by Cheryl Axelrod, M.D., ob-gyn
Written by Karen Miles

Headshot of Karen Miles, author specializing in pregnancy and health topics.

Is Losing Weight While Pregnant Safe?

No matter your pre-pregnancy weight, actively trying to lose weight while pregnant is typically not considered safe. The single exception might be in the very early weeks, which we will discuss further. The impact of a mother’s weight on her developing baby is complex and continuously studied by experts. However, there’s broad consensus that losing weight during pregnancy, outside of specific early circumstances, is incompatible with supporting healthy fetal growth. Furthermore, intentional weight loss through dieting can lead to a deficiency in calories and essential nutrients needed for a healthy pregnancy.

Risk of Losing Weight During Pregnancy

While carrying excess weight before pregnancy can increase risks for complications, losing weight during pregnancy generally puts you at risk of having a baby who is small for gestational age (SGA) and potentially for preterm birth. It’s vital to provide a consistent supply of energy and nutrients to your growing baby.

Weight Loss in the First Trimester: What’s Normal?

It’s quite common and often considered normal to experience some weight loss during the first trimester of pregnancy. Several factors can contribute to this:

• Morning sickness: Nausea and vomiting are prevalent symptoms in the first trimester. This can significantly reduce your appetite and cause you to lose calories, leading to a decrease in weight. Don’t worry excessively about your baby’s calorie needs at this very early stage; they are tiny and will typically get what they need from your existing reserves. It is generally considered safe to lose weight first trimester under these circumstances.
• Fat reserves: Women who started their pregnancy overweight or obese have stored energy in fat. As your baby begins to grow, using a small amount of this reserve is not usually harmful, and may result in maintaining or slightly losing weight initially.
• Improved lifestyle: If you started exercising or switched to healthier eating habits once you found out you were pregnant, you might lose a few pounds early on.

In most cases, this type of weight loss in the first trimester isn’t dangerous. However, if you are losing a significant amount of weight rapidly, or if you suspect you might be suffering from hyperemesis gravidarum (severe morning sickness leading to extreme nausea and vomiting), you must inform your healthcare provider immediately.

Pregnancy Weight Gain Guidelines for Overweight or Obese Women

If you were overweight or obese before becoming pregnant, you are not alone; more than half of pregnant women fall into these categories. Your pre-pregnancy body mass index (BMI) is used to determine if you are overweight (BMI between 25 and 29.9) or obese (BMI of 30 or greater). BMI is an estimate of body fat based on height and weight.

While it’s not safe to lose weight intentionally during pregnancy, if you are overweight or obese, your healthcare provider might recommend gaining less than the standard guidelines for women of average weight. The Institutes of Medicine (IOM) provides general recommendations based on pre-pregnancy BMI:

• If your BMI is 25 to 29.9 (overweight): The recommendation is to gain between 15 and 25 pounds throughout the entire pregnancy. This translates to approximately 2 to 3 pounds per month during the second and third trimesters.
• If your BMI is 30 or higher (obese): The advice is to gain 11 to 20 pounds during pregnancy.

There has been some discussion and research suggesting that for some women with obesity, gaining less than the IOM recommended 11-20 pounds (e.g., 6 to 14 pounds) may still result in healthy neonatal outcomes. If you are overweight or obese, it is crucial to discuss your specific target weight gain with your healthcare provider. If you aim for a lower gain, they will need to monitor you and your baby closely to ensure healthy progression and growth.

Should You Diet to Lose Weight While Pregnant?

Pregnancy is emphatically not the time to embark on a weight-loss diet, regardless of your starting weight. Restricting your food intake poses potential hazards to both you and your developing baby. You require sufficient calories and a wide range of nutrients to support a healthy pregnancy.

Avoid restrictive diets, particularly very low-carbohydrate plans like keto or Atkins. Your baby’s growth and development rely on carbohydrates. Ongoing ketosis caused by such diets can be harmful to a developing fetus. Instead of focusing on rapid weight loss methods like how to lose 5 pounds in 2 days or using techniques like how to lose weight in 1 day with water, concentrate on nourishing yourself and your baby.

Healthy Habits for Managing Pregnancy Weight Gain

While you shouldn’t diet to lose weight, you can manage your pregnancy weight gain within the healthy target range by focusing on balanced nutrition and regular, safe exercise (approved by your provider). Aim to:

• Consume balanced meals and incorporate healthy snacks throughout the day.
• Stay well-hydrated by drinking approximately ten 8-ounce cups of water daily.
• Choose complex carbohydrates, such as whole grains, beans, fruits, and vegetables, over simple carbohydrates like white bread or white rice.
• Monitor your weight gain alongside your healthcare provider during your prenatal appointments to stay on track.

Pregnant woman sitting on a bench, looking at her phone, representing expectant mothers seeking information about pregnancy.

When to Worry: Weight Loss in Later Pregnancy

Experiencing weight loss during the second or third trimester can sometimes indicate an underlying issue. While minor fluctuations can occasionally be harmless (like water loss after temporary fluid retention), it is essential to inform your healthcare provider if you notice weight decreasing in these later stages.

Your provider will assess your diet and activity levels and ask about symptoms that might discourage eating, such as persistent nausea, heartburn, bloating, or constipation. They may also consider screening for conditions like depression or fetal growth restriction, as these can sometimes be associated with insufficient weight gain or loss. Report any sudden, dramatic weight loss, such as five pounds in a single week, to your provider immediately.

In summary, while some modest weight loss may occur and be deemed normal during the first trimester, actively trying to lose weight by dieting during pregnancy is generally unsafe and not recommended. Focusing instead on healthy eating, regular exercise, and consistent monitoring with your healthcare provider is the best approach to ensure a healthy pregnancy and support your baby’s growth, regardless of your starting weight.