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Pregnancy Weight Gain Calculator

Created by Łukasz Białek, MD and Bogna Szyk
Reviewed by Dominik Czernia, PhD and Jack Bowater
Based on research by
U.S. Department of Agriculture and U.S. Department of Health and Human Services Dietary Guidelines for Americans, 2020-2025. 9th edition: Chapter 5 - Women Who Are Pregnant or Lactating;; December 2020See 1 more source
Institute of Medicine (US) and National Research Council (US) Committee to Reexamine IOM Pregnancy Weight Guidelines. Weight Gain During Pregnancy: Reexamining the Guidelines.;; May 2009
Last updated: Jan 18, 2024

This pregnancy weight gain calculator is a handy tool for estimating how much weight you should gain during pregnancy. You can use it to determine the pregnancy weight gain week by week. Remember that these values are only approximate, though - don't worry if your weight gain is a bit faster or slower. In this article, you will learn about different changes that happen to a pregnant woman's body and why it is so important to follow your weight gain during pregnancy. We will also tell you what is a normal weight gain in pregnancy and point out what kind of weight fluctuations you should be concerned about and what can they mean.

Expecting a baby? Make sure to check what height and blood type they will probably have!

Changes in the body during pregnancy

Is your period late? Do you have morning sickness? Do you feel tired most of the time? If you are answering Yes to those questions, it means that you are probably pregnant. Congratulations!

Usually, pregnancy lasts 40 weeks from the last menstrual period or 38 weeks from fertilization (but it is generally counted from the last menstrual period). Pregnancy is typically divided into three trimesters:

  1. trimester - first 12 weeks
  2. trimester - from 13th till 28th week
  3. trimester - from 29th week till childbirth

A lot of women feel fear about pregnancy and the changes it causes to their bodies. They are afraid of stretch marks, urinary infections, pain, and going through labor. There is even a medical term tokophobia, which is an unspecified phobic anxiety disorder classified by the International Classification of Disease! But these are not the only changes that occur to the body of a pregnant woman. There are specific breast changes (they are larger and the areolae are darker), significant changes in hormone regulation, the arterial pressure lowers (due to dilatation of vessels by progesterone), cardiac output increases by 30-50%, heart rate increases by 25%, blood volume increases by even 45% as well as vital capacity. All these changes have three major reasons:

  1. To enable appropriate growth for the baby;
  2. To prepare for the labor; and
  3. To prepare for breastfeeding after the childbirth.

It is also worth remembering and knowing that although pregnancy is not a disease, it may predispose the woman to certain conditions. These include tooth decay, urinary and other infections, heartburn, constipation, hemorrhoids, cholelithiasis, hypertension, etc.

And last but not least there is a change in the weight of a pregnant woman!

Why do you gain weight during pregnancy?

Pregnancy can lead to changes in many of your daily routines and habits, including what you eat and how much exercise you get. But most of all: women's bodies change during pregnancy to ensure that their unborn child gets enough food and other things they need. These changes already start happening in early pregnancy and become more and more noticeable as time goes on. Women gain more weight in the final months of pregnancy than they do in the first few months (look at the pregnancy weight gain timeline generated by our calculator).

There are various reasons women gain weight during pregnancy and many different body areas where they gain it. First, of course, is the baby itself. Then there are the changes to your body that support your pregnancy and what will happen after childbirth. You gain fat, which your body is going to use to store nutrients for breastfeeding; your breasts increase (and this is also additional weight!), and you gain weight from your enlarged uterus, placenta, and amniotic fluid. The rest of your weight gain comes from the increased blood and body fluid.

Prenatal care importance

In the US, prenatal care for so-called low-risk pregnancies usually consists of 8 visits to a healthcare professional. On each of them, there are particular procedures performed which vary depending on the particular visit. They include medical history, abdominal and vaginal examination, blood pressure measurement, blood type identification, urinalysis, HIV and syphilis testing, vaccination and education. During the first visits a very important part of the examination might be β-hCG levelcontrol. One of the most important parts of every visit is measuring the weight of the woman. It suggests that even though it is a straightforward measurement, it may be beneficial in screening the pathologies during pregnancy.

It is obvious that over time a pregnant woman weighs more and more. But what is healthy pregnancy weight gain? How much more is enough? And how much more is way too much? Is my current weight within the limit of normal weight gain in pregnancy? Keep on reading to get this information!

Pregnancy weight gain by week and by trimester

In pregnancy, ideal weight is different than in non-pregnant women. Are you wondering how much weight should you gain during pregnancy? Or maybe you think it is a fixed number of pounds or a fixed percentage of your pre-pregnancy weight?

Let's check the truth! Pregnancy weight gain depends on two main factors: your pre-pregnancy BMI and the type of pregnancy (singleton or twin).

  • If you were underweight (BMI below 18.5), you should gain between 28 and 40 pounds during your pregnancy.
  • If your BMI was normal (18.5–24.9), you should gain between 25 and 35 pounds (and 37 to 54 pounds if you're carrying twins).
  • If you were overweight (BMI between 25 and 29.9), you should gain between 15 and 25 pounds (and 31 to 50 pounds for a twin pregnancy).
  • Finally, if you were obese before the pregnancy (BMI over 30), you should gain between 11 and 20 pounds (25 to 42 pounds during a twin pregnancy).

This weight gain is your target for the 40th week. During your pregnancy, however, you can and even should monitor the changes in your weight as well. The Institute of Medicine of the National Academies suggests a distribution of pregnancy weight gain by week; we built this calculator according to their guidelines so you can check whether your weight is in the recommended range.

During the first trimester, you will probably gain 3-4 pounds in total only - your baby is still tiny, and morning sickness may prevent you from gaining any weight at all. Most of your weight gain will occur during the second trimester. In the third, even though you will still keep gaining weight, the increase will slow down, especially during the ninth month.

Use our pregnancy weight gain calculator to receive the full information about typical weight gain in pregnancy, tailored for you.

How to use the pregnancy weight calculator?

Check these few steps to find your healthy weight gain during pregnancy:

  1. Enter your height and pre-pregnancy weight into appropriate boxes.
  2. The pregnancy weight gain calculator will automatically determine your pre-pregnancy BMI.
  3. Mark whether you are expecting twins or not - this will heavily influence your weight gain.
  4. Choose the week of pregnancy.
  5. The pregnancy weight gain calculator will determine the minimum and maximum recommended weight gain since the beginning of pregnancy - these values are approved by The Institute of Medicine of the National Academies. It will also add these values to your initial weight.

You can also take a look at the graph below the pregnancy weight calculator on the left. Thanks to it, you can also check how much weight you should gain in a particular week of pregnancy and how much it should change on the timeline.

How to weigh yourself?

First of all, don't stress too much - in pregnancy, you don't have to weigh yourself every day. The day-to-day fluctuations, often caused by a big dinner the day before, can really drive you crazy. It's enough to weigh yourself once a week. Remember always to do it at the same time of the day, wearing the same amount of clothes, and using the same scale. Later you can check your measurements on the timeline graph below our pregnancy weight calculator to ensure that you are doing well.

What to eat to maintain appropriate weight gain during pregnancy?

During pregnancy, normal weight gain is crucial for the proper development of the baby - maternal obesity can be linked to, e.g., an increased number of stillbirths and neonatal deaths. You should remember that a healthy diet is an essential part of your lifestyle at any time, but it is especially vital if you're pregnant or planning a pregnancy. But what do we mean by a healthy diet? Many mamas-to-be wonder what they should eat and what is the right diet for a pregnant woman?

The most important thing to remember is that you don't need to go on any special diet. However, it's important to eat different foods every day to get all the necessary nutrients that you and your baby needs. It's best to get the vitamins from the food, not the dietary supplements. However, the supplementation of folic acid is also necessary.

During pregnancy, women are usually hungrier than usual so they can and should eat more, but you don't need to eat for two. Don't count calories in pregnancy! Eat plenty of fruit and vegetables because these provide vitamins and minerals, as well as fiber, which helps digestion and can help prevent constipation - which often happens in pregnant women. Avoid snacking on foods that are high in fat and sugar. Eliminate alcohol and cigarettes. Eat protein foods, such as beans, meat, fish, eggs every day. However, avoid raw meat, as it may be a source of infection.

Prepare your meals safely:

  • wash fruits, vegetables, and your hands,
  • use a separate knife and chopping board for raw meats,
  • store raw foods separately from ready-to-eat foods.

Remember also about other healthy habits: have some regular physical activity (if everything during pregnancy is fine), sleep long enough, drink plenty of water, and don't smoke!

What if I gain too much or too little weight?

Don't fret if your weight differs from the recommended one only slightly. Your pregnancy will, most likely, not follow the "ideal" weight gain distribution. As soon as you approach your target weight, you should be fine. Watch out for the following, though, as they might be some worrying signals:

  • gaining more than three pounds in one week of the second trimester;
  • gaining more than two pounds in one week of the third semester;
  • gaining no weight at all for more than two weeks in a row during months 4 - 8.

Women who gain a lot of weight in pregnancy have a higher risk of specific health problems and complications during childbirth. For instance, they are more likely to have a hefty baby with a birth weight of over 4,000 g or 4,500 g (macrosomia) and are more likely to need a Cesarean section. They are also more likely to have difficulties losing the extra weight after giving birth. Gaining too much weight might also cause other problems, from simple discomfort and back pain to trouble reading the ultrasound results, and even preeclampsia (gestational hypertension plus proteinuria) and premature labor.

On the other hand, if a woman doesn't gain enough weight and doesn't get enough different foods in pregnancy, it can harm her growing baby: babies are then often born too early (preterm birth) or often weigh too little at birth. Gaining too little weight maybe even more dangerous for the baby as we realize that small premature infants have more problems in the neonatal intensive care units.

If you are in any of the situations mentioned above, don't forget to consult your doctor!

Do we need to change the social norms?

The current obesity epidemic has brought the topic of weight into focus, not only among scientists. Nowadays, the importance of living healthier is clear to more and more people worldwide. For women, pregnancy has been identified as an important area of study for weight control, as excessive weight gain during pregnancy leads to many health complications. Then why have women come to embrace pregnancy as a time to gain weight freely? Dr. Jennifer Kraschnewski from Penn State College of Medicine stated in her article that it is mainly due to social norms, which can be summarized by the commonly used phrase "eating for two." "In truth, only an additional 300 calories a day are needed to achieve the 25-35 pound weight gain recommended for normal-weight women", says Dr. Kraschnewski in her article.

Moreover, according to an article published by Phelan in American Journal of Obstetrics and Gynecology, we should notice that pregnancy is a recognized teachable moment, when women are highly motivated to engage in healthy behaviors, such as smoking cessation or having a healthy diet. The problem is that adopting optimal health behaviors is impossible when there is confusion about how should it look like. This is why we cannot give up in educating the society about real, scientifically proven, healthy diet for pregnant women.

Pregnancy weight gain series

We introduced a series of articles based on pregnancy weight changes - go ahead and find your answers in one of them!


When do you start gaining weight in pregnancy?

In pregnancy, the most apparent weight gain happens in the second trimester. You gain weight the moment the baby starts growing, but during the first trimester they're still relatively tiny. The first weeks of pregnancy often involve morning nausea, which may prevent you from noticing extra pounds. In the third trimester (from 29. weeks), you still gain weight, but at a slower pace.

How much weight will I gain during pregnancy if I weigh 122 lbs?

If you weight 122 lb, you should gain approximately:

  • 25-35 lbs if your weight before pregnancy was within the normal range (BMI 18.5-24.9);
  • 15-25 lbs if before pregnancy you were overweight (BMI 25-29.9);
  • 11-20 lbs if before pregnancy you were obese (BMI 30 and more); and
  • 28-40 lbs if before pregnancy you were underweight (BMI less than 18.5).

Do I gain weight faster in my second pregnancy?

Weight gain in the second pregnancy is approximately the same as in the first one. However, you might have the impression of gaining extra pounds faster. One possible reason is the starting point - you might not have shed additional weight from the first pregnancy yet. The pregnancy is also more apparent. Abdominal muscles, ligaments, and uterus never come back to the original shape after a child - which makes your second pregnancy baby bump more prominent.

How much weight should a teenager gain during pregnancy?

According to Institute of Medicine, teenage pregnancy recommendations do not differ from adult pregnancy recommendations. Adolescents during pregnancy should gain 11-40 lbs, depending on their pre-pregnancy body mass index (BMI). BMI is an index for adults, and it will misclassify some teenagers as underweight. Still, a pregnant teenager needs to not only support the growth of the baby, but also of themselves. That's why a more prominent weight gain might be appropriate.

Łukasz Białek, MD and Bogna Szyk
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