Pregnancy weight gain is a natural and necessary part of pregnancy to support the growth and development of the fetus. How much weight a person gains depends on several factors, including their prepregnancy weight.

A pregnant person needs to meet recommended weight gain goals depending on their prepregnancy weight and body mass index (BMI).

Gaining less or more weight than the recommendations can have health implications.

This article examines pregnancy weight gain guidelines and how much a person should gain per trimester. We also discuss losing and gaining too much weight during pregnancy and how a person can stay healthy during pregnancy.

A female in the later stages of pregnancy walking at night.Share on Pinterest
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Pregnancy weight gain varies greatly and depends on various factors, including:

  • prepregnancy weight
  • prepregnancy body mass index (BMI)
  • twin or multiple pregnancy
  • stage of pregnancy, or trimester
  • overall health of fetus

BMI measures a person’s body fat based on weight and height.

While there is no standardized approach to pregnancy weight gain, below are general guidelines for pregnancy weight gain for a person carrying a single baby:

Prepregnancy weightRecommended weight gain
Underweight — BMI less than 18.528–40 lb
Normal, or moderate, weight — BMI 18.5–24.925–35 lb
Overweight — BMI 25–29.915–25 lb
Obese — BMI greater than or equal to 3011–20 lb

There are different guidelines for pregnant people carrying twins, but they generally need to gain more weight.

A person carrying triplets or more should talk with a healthcare professional to discuss their weight gain goals.

How much weight a person needs to gain during pregnancy and the extra calories they need vary by trimester.

The American College of Obstetricians and Gynecologists (ACOG) offers some general guidelines for a person with a moderate prepregnancy BMI carrying one fetus:

  • First trimester: A person does not need extra calories during the first trimester. They may gain no weight to only about 1–5 pounds (lb) during the first trimester.
  • Second trimester: A person needs an extra 340 calories per day during the second trimester. They may gain about 0.5–1 lb per week.
  • Third trimester: A person needs an extra 450 calories per day during the third trimester. They may gain about 0.5–1 lb per week.

ACOG states that a person carrying multiples requires an extra 300 calories for each fetus. Therefore, someone pregnant with twins needs an extra 600 calories per day. For triplets and more, a person should talk with their doctor.

A person who is underweight or obese should also consult their doctor about developing a nutrition plan during pregnancy.

Learn more about pregnancy trimesters here.

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Pregnancy weight gain: Where the weight goes during pregnancy. Infographic by Yaja Mulcare.

The baby accounts for just 7–8 lb of a person’s pregnancy weight gain. However, much of the pregnancy weight is related to the baby and is not fat.

The recommended weight gain for a person with a moderate BMI is 25–35 lb. This allocates to:

  • baby: 7–8 lb
  • placenta: 2–3 lb
  • amniotic fluid: 2–3 lb
  • breasts: 2–3 lb
  • blood supply: 4 lb
  • uterus: 2–5 lb
  • fat stores for delivery and breastfeeding or chestfeeding: 5–9 lb

It is not usually a cause for concern if a person is a few pounds outside this weight gain range if other aspects of the pregnancy are healthy.

Gaining weight during pregnancy is natural to ensure a healthy pregnancy and support the development and growth of the fetus.

Therefore, doctors do not recommend pregnant people diet or lose weight, even if they are overweight.

If a person is very overweight when pregnant, their doctor may ask them to lose weight. However, they should only do this under their doctor’s advice and care.

Putting on too much weight during pregnancy may affect a pregnant person and their child.

A person may be at an increased risk of pregnancy-related complications, including:

The baby may be born larger than average, known as macrosomia. They are also more likely to develop health problems later in life, including obesity and heart disease.

The following tips may help a person stay healthy during pregnancy:

  • Eat a healthy, balanced diet. This includes a wide variety of foods, especially lean protein, whole grains, low fat dairy, vegetables, and fruits. Limit consumption of added sugars and solid fats. Be cautious or avoid foods that are not safe during pregnancy.
  • Stay active. Physical activity is safe and healthy for pregnant people unless advised otherwise by a healthcare professional. Walking and swimming are examples of safe and effective exercises during pregnancy.
  • Drink plenty of water. Pregnant people should drink 8–12 cups of water. This is important in producing amniotic fluid, helping nutrients circulate throughout the body, and flushing toxins.
  • Take supplements. A pregnant person may ask their healthcare professional what supplements they need. Generally, a person only requires folic acid and iodine during pregnancy. Some may need other supplements based on their individual risk factors.
  • Work with a healthcare professional. A doctor will monitor a pregnant person’s weight and overall pregnancy health throughout the pregnancy. A dietitian may also help plan how to boost or cut down on calories, as needed.

A person should communicate with their health professional throughout pregnancy.

They may talk with their doctors if they want to know whether they are meeting their weight goals or need support preparing a healthy diet plan. It is essential for people to inform a doctor if they notice any of the following:

  • unintentional weight loss in the second or third trimester
  • gaining too little weight or lack of weight gain
  • the feeling of gaining too much weight
  • presence of an eating disorder
  • rapid weight gain, which can be a sign of preeclampsia

Pregnancy weight gain is a natural and necessary part of pregnancy to support the growth and development of the fetus.

The expected weight gain varies per individual and depends on several factors, such as prepregnancy weight.

A person should work closely with their healthcare professional to meet their pregnancy weight gain target and keep their overall pregnancy health in check.

This is crucial in preventing pregnancy-related complications associated with gaining too much or too little weight.