Pregnancy Weight Gain Calculator
Track Healthy Weight Gain Throughout Your Pregnancy Journey
Pregnancy Weight Gain Calculator
Calculate Your Recommended Weight Gain
Recommended Weight Gain by BMI
Understanding Pregnancy Weight Gain
Pregnancy weight gain is essential for supporting fetal growth, placental development, and maternal physiological changes that prepare the body for childbirth and breastfeeding. Gaining appropriate weight reduces risks of pregnancy complications, preterm birth, low birth weight, and cesarean delivery. However, both insufficient and excessive weight gain carry health risks, making it crucial to aim for the recommended range based on pre-pregnancy BMI.
The Institute of Medicine (IOM) guidelines provide weight gain recommendations based on pre-pregnancy Body Mass Index (BMI). Women with normal BMI (18.5-24.9) should gain 25-35 pounds total. Underweight women (BMI <18.5) need 28-40 pounds to support both maternal and fetal health. Overweight women (BMI 25-29.9) should gain 15-25 pounds, while obese women (BMI ≥30) should gain 11-20 pounds. These ranges minimize complications while ensuring adequate fetal nutrition. Women carrying twins need higher gains: 37-54 pounds for normal weight, 31-50 for overweight, 25-42 for obese.
Weight gain isn't linear—most occurs in second and third trimesters. First trimester gain is typically only 1-4 pounds (sometimes weight loss from morning sickness). In second and third trimesters, women with normal BMI gain about 1 pound per week (0.5-0.7 lbs/week for overweight, 0.4-0.6 lbs/week for obese). Rapid weight gain (>3 pounds in one week) or no weight gain for several weeks warrants medical evaluation. Weight gain composition includes: baby (7-8 lbs), placenta (1-2 lbs), amniotic fluid (2 lbs), uterus enlargement (2 lbs), breast tissue (1-2 lbs), blood volume increase (3-4 lbs), maternal fat stores (6-8 lbs), and fluid retention (2-3 lbs).
Where Pregnancy Weight Goes
Weight Distribution (35 lb total gain)
| Baby | 7-8 lbs |
| Placenta | 1.5-2 lbs |
| Amniotic fluid | 2 lbs |
| Uterus | 2 lbs |
| Breast tissue | 1-2 lbs |
| Blood volume | 3-4 lbs |
| Maternal fat stores | 6-8 lbs |
| Extra fluid | 2-3 lbs |
Understanding where weight goes helps contextualize pregnancy weight gain as necessary physiological changes rather than "getting fat." The baby accounts for only 20-25% of total weight gain. Blood volume increases 40-50% to support placental circulation—this alone adds 3-4 pounds. Breast tissue enlarges in preparation for lactation. The uterus expands from pear-sized (2-3 oz) to watermelon-sized, adding 2 pounds. Maternal fat stores (6-8 lbs) provide energy reserves for late pregnancy and breastfeeding when caloric demands peak. After delivery, women immediately lose 12-14 pounds (baby, placenta, amniotic fluid). The remaining 10-25 pounds gradually decrease over 6-12 months through breastfeeding, metabolism, and postpartum recovery.
Weight Gain Pattern by Trimester
First Trimester (Weeks 1-12): 1-4 lbs Total
Minimal weight gain is normal in the first trimester—typically only 1-4 pounds total, or even weight loss for women experiencing severe morning sickness. The developing embryo is tiny (less than 3 inches by week 12), requiring minimal additional calories. Many women don't need extra calories in the first trimester. Weight loss from nausea/vomiting is common and usually not concerning unless severe (hyperemesis gravidarum requiring medical intervention). Focus on staying hydrated, eating nutrient-dense foods when possible, taking prenatal vitamins, and managing morning sickness rather than worrying about weight gain.
Second Trimester (Weeks 13-27): ~1 lb/week
Steady weight gain begins in the second trimester when morning sickness typically subsides and appetite returns. Women with normal pre-pregnancy BMI should gain approximately 1 pound per week (14-15 pounds total for second trimester). Overweight women target 0.5-0.7 lbs/week; obese women 0.4-0.6 lbs/week. The fetus grows from 3 inches to 14 inches, increasing caloric needs. Add 300-350 extra calories daily (e.g., apple with peanut butter, Greek yogurt with berries, whole grain toast with avocado). This is when baby bump becomes visible as uterus expands above pubic bone.
Third Trimester (Weeks 28-40): ~1 lb/week
Continued steady gain through the third trimester as baby gains about half its birth weight in the final 6-8 weeks. Target remains approximately 1 pound per week for normal BMI women (12-13 pounds total for third trimester). Some women's weight gain slows or plateaus in the final 2-3 weeks before delivery—this is normal. Add 450 extra calories daily in third trimester. Weight gain may include increased fluid retention (edema) in ankles, feet, and hands, especially in the final weeks. Sudden excessive weight gain (>3 lbs in one week) combined with swelling, headaches, or vision changes may indicate preeclampsia—seek immediate medical evaluation.
Factors Affecting Pregnancy Weight Gain
Multiple Pregnancy (Twins/Triplets)
Multiple pregnancies require higher weight gain to support multiple babies and placentas. For twins: normal weight women should gain 37-54 pounds, overweight 31-50 pounds, obese 25-42 pounds. Weekly gain targets are higher: 1.5 pounds/week for normal BMI. Triplets require even more (50-60+ pounds total). Higher weight gain reduces risks of preterm birth and low birth weight, which are more common with multiples. Multiple pregnancies also require increased calories (600-900 extra daily by third trimester vs. 450 for singletons), more frequent prenatal monitoring, and often earlier delivery planning.
Age & Parity (Previous Pregnancies)
Maternal age influences weight gain patterns—teenagers still growing themselves need higher gains (upper end of range for BMI category). Women over 35 may gain less and face higher risks from excessive gain (gestational diabetes, preeclampsia). Parity matters: First-time mothers often gain more weight than in subsequent pregnancies. Women who didn't lose all pregnancy weight between pregnancies start higher BMI and may need modified targets. Short intervals between pregnancies (<18 months) don't allow adequate recovery, potentially affecting weight gain recommendations and outcomes.
Gestational Diabetes
Gestational diabetes (GDM) affects 6-9% of pregnancies and requires careful weight management. Excessive pre-pregnancy weight and rapid early pregnancy gain increase GDM risk. If diagnosed with GDM, closely monitored weight gain within recommended ranges is crucial—excessive gain worsens blood sugar control and increases risks of large baby (macrosomia), difficult delivery, and cesarean. GDM management includes blood sugar monitoring, carbohydrate-controlled diet, regular physical activity, and possibly insulin. Weight gain targets typically remain within IOM guidelines but are individualized based on blood sugar control and fetal growth patterns.
Morning Sickness & Hyperemesis
Severe morning sickness can cause weight loss in early pregnancy. Mild nausea affecting 70-80% of pregnancies may limit first trimester gain to 0-2 pounds. Hyperemesis gravidarum (severe, persistent vomiting) affects 1-3% of pregnancies, causing weight loss >5% of pre-pregnancy weight, dehydration, electrolyte imbalances, and potential hospitalization for IV fluids and anti-nausea medications. Women who lose significant weight from hyperemesis should gain it back plus the full recommended amount—weight loss doesn't count toward total gain goals. Focus on staying hydrated, eating small frequent meals, taking prenatal vitamins, and seeking medical help if unable to keep food/fluids down.
Tips for Healthy Pregnancy Weight Management
- Eat nutrient-dense foods: Focus on fruits, vegetables, whole grains, lean proteins, dairy, healthy fats. Avoid empty calories from sugary drinks, candy, processed snacks.
- Don't "eat for two": You only need 0 extra calories in first trimester, 300-350 extra in second, 450 extra in third. Quality matters more than quantity.
- Exercise regularly: 150 minutes moderate activity weekly (walking, swimming, prenatal yoga) helps manage weight gain, reduces gestational diabetes risk, eases labor.
- Track weight weekly: Weigh yourself weekly at same time/day. Notify provider if gaining >3 lbs in one week or no gain for 2+ weeks.
- Eat smaller, frequent meals: 5-6 small meals daily instead of 3 large ones helps with nausea, heartburn, blood sugar stability, and prevents overeating.
- Stay hydrated: Drink 8-12 cups water daily. Adequate hydration supports blood volume increase, prevents constipation, reduces swelling.
- Choose healthy snacks: Greek yogurt with fruit, nuts, vegetables with hummus, whole grain crackers with cheese, hard-boiled eggs instead of chips/cookies.
- Limit processed foods: Minimize fast food, fried foods, sugary desserts, sodas. These add calories without nutrients needed for fetal development.
- Get adequate sleep: 7-9 hours nightly supports healthy metabolism, reduces stress eating, and helps regulate hunger hormones (leptin, ghrelin).
- Work with healthcare providers: Discuss weight gain goals, receive personalized guidance based on BMI, monitor progress, address concerns early.
Medical Disclaimer
This pregnancy weight gain calculator provides estimates based on Institute of Medicine (IOM) guidelines but cannot account for individual variations, multiple pregnancies, medical conditions, or complications affecting appropriate weight gain. Calculated recommendations are general guidelines—actual targets should be personalized by healthcare providers based on pre-pregnancy BMI, medical history, pregnancy complications (gestational diabetes, preeclampsia, growth restrictions), multiple pregnancy, maternal age, and ongoing maternal-fetal health monitoring. This calculator cannot diagnose weight-related complications, predict pregnancy outcomes, or replace prenatal care. Excessive or insufficient weight gain can indicate underlying issues requiring medical evaluation. Sudden rapid weight gain (>3 pounds in one week) especially with headaches, vision changes, or severe swelling may indicate preeclampsia requiring emergency care. Inadequate weight gain may signal poor fetal growth, nutritional deficiencies, or hyperemesis requiring intervention. Weight loss attempts or restrictive dieting during pregnancy are dangerous and should never be undertaken without medical supervision for specific health conditions. Always consult obstetricians, certified nurse-midwives, registered dietitians, or healthcare providers for personalized weight gain targets, nutrition counseling, exercise guidance, and monitoring throughout pregnancy. This tool is for educational and tracking purposes only, not medical advice, diagnosis, or treatment.
About the Author
Adam
Co-Founder @ RevisionTown
Math Expert specializing in various curricula including IB, AP, GCSE, IGCSE, and more
Recommended weight gain during pregnancy
Pregnancy can lead to significant changes to women’s bodies and daily routines. One such change is weight gain to ensure that there are enough nutrients for the development of the fetus as well as to store enough nutrients in preparation for breastfeeding. While weight gain during pregnancy is normal and necessary, studies have shown that certain ranges of weight gain given a specific body mass index (BMI) result in more positive outcomes for both fetus and mother.1
Generally, it is recommended that pregnant women gain only 1-4 pounds during the first 3 months of pregnancy, and 1 pound per week during the remainder of the pregnancy. It is possible to achieve 1 pound per week by consuming an additional ~300 calories per day,2 which is roughly equivalent to eating an extra sandwich plus a glass of milk or a baked potato plus 2 ounces of meat plus an apple.
The Institute of Medicine provides a weight gain guideline based on Prepregnancy BMI, which is shown in the table below. But note that these are only recommendations and that weight gain between women varies. As such, a health care provider should be consulted to more accurately determine each person’s specific needs.
Recommendations for total weight gain during pregnancy by prepregnancy BMI1
| Prepregnancy BMI (kg/m2) | Category | Total Weight Gain Range | Total Weight Gain Range for Pregnancy with Twins |
| <18.5 | Underweight | 28-40 lbs | |
| 18.5-24.9 | Normal Weight | 25-35 lbs | 37-54 lbs |
| 25.0-29.9 | Overweight | 15-25 lbs | 31-50 lbs |
| >30.0 | Obese | 11-20 lbs | 25-42 lbs |
Weight gain during pregnancy is not just attributed to the weight of the fetus. Most of the weight gain goes to the development of tissues that allow fetal development, growth, and prepare the body for breastfeeding. The table below is a list.
Pregnancy weight gain distribution2
| Enlarged breasts | 1-3 pounds |
| Enlarged uterus | 2 pounds |
| Placenta | 1.5 pounds |
| Amniotic fluid | 2 pounds |
| Increased blood volume | 3-4 pounds |
| Increased fluid volume | 2-3 pounds |
| Fat stores | 6-8 pounds |
Potential complications of suboptimal weight gain
There are adverse effects for either insufficient or excessive weight gain during pregnancy. Insufficient weight gain can compromise the health of the fetus and cause preterm, or premature birth; excessive weight gain can cause labor complications, giving birth to significantly larger than average fetuses, postpartum weight retention, as well as increase the risk of requiring a cesarean section (C-section).
What to eat during pregnancy?
What a person eats, or doesn’t eat, during pregnancy can significantly affect the health of their baby. Although what a person should or shouldn’t eat during their pregnancy is often heavily debated, and can be different between cultures, there is no particular formula that guarantees a healthy baby, and though a parent should be careful and cognizant of what they choose to put in their bodies, it is not absolutely necessary to follow some heavily strict, nutritional guideline during pregnancy. General advice for eating healthy applies, such as eating a balance of vegetables, fruits, whole grains, lean proteins, and healthy fats. Certain nutrients can, however, be particularly helpful for the growth and development of a healthy baby. Some of these will be discussed below.
Folate and folic acid:
Folate and folic acid can help prevent birth defects. Folate, in particular, protects against neural tube defects as well as potential abnormalities in the brain and spinal cord. It has also been shown to decrease the risk of premature birth. Folic acid is the synthetic form of folate, a B vitamin, and can be consumed in the form of supplements, or fortified foods. Aside from using supplements, folic acid can be consumed through eating certain leafy green vegetables (spinach), citrus fruits (oranges), dried beans, and peas.
Calcium:
Calcium helps support strong bones and teeth, and is also necessary for the proper day-to-day functioning of the body’s circulatory, muscular, and nervous systems. Calcium can be found in dairy products such as milk, yogurt, and cheese. It can also be found in non-dairy foods such as spinach, salmon, broccoli, and kale.
Vitamin D:
Like calcium, vitamin D can help promote bone strength while also building the baby’s bones and teeth. It can be found in fortified milk, orange juice, fish, and eggs, among other foods.
Protein:
Protein, while being important for your own health, is also highly important for the growth of the baby throughout pregnancy. Good sources of protein include lean meat, poultry, fish, eggs, beans, peas, nuts, and soy products, among others.
Iron:
Iron is another nutrient that is highly important for the development of your baby. A pregnant person should consume double the amount of iron than they otherwise would, because iron is essential for the body to produce more blood to supply oxygen to the baby. In the case where the mother is not consuming sufficient iron, the mother could suffer from iron deficiency anemia, resulting in fatigue, and increasing the risk of having a premature birth. Iron can be found in lean red meat, poultry, fish, iron-fortified foods, beans, and vegetables, among other foods. Iron from animal products is most easily absorbed through pairing iron from plant sources with foods or drinks that contain high amounts of vitamin C can increase the absorption of iron.
Most of the nutrients listed above can be obtained through some form of supplements, and taking prenatal vitamins is fairly common. Depending on your diet, you may consider speaking to a healthcare professional to determine if you should take a prenatal vitamin or any other special supplements.
Foods to avoid:
It is as important to avoid certain foods and activities during pregnancy as it is to consume foods with specific nutrients. Some of these include foods that are high in mercury, like many kinds of seafood. Generally, the bigger and the older a fish is, the more mercury it likely contains. The FDA recommends that pregnant women avoid eating shark, swordfish, king mackerel, and tilefish. The kinds of seafood that are generally considered safe include shrimp, salmon, pollock, catfish, anchovies, trout, cod, tilapia, and light canned tuna, among others.
Pregnant women should also avoid consuming foods that are raw, undercooked, or of course, contaminated. These include foods such as sushi, sashimi, and raw shellfish like oysters, scallops, and clams. Similarly, undercooked meat, poultry, and eggs should also be avoided, since pregnant women are at higher risk of food poisoning due to bacteria in undercooked foods.
Unpasteurized foods, which include many dairy products, should also be avoided since they can lead to food-borne illnesses.
Pregnant women also should not eat unwashed fruits and vegetables, again because of the potential for consuming harmful bacteria. Certain sprouts like alfalfa, clover, radish, and mung bean can contain disease-causing bacteria, and should be cooked thoroughly and not eaten raw.
Excess caffeine should also be avoided, since it can cross the placenta, and the effects on the baby are not well known. Herbal teas are also not well studied, and the effects they may have on the baby are not well known.
Under no circumstances should a pregnant woman consume alcohol, as no study has found a level of alcohol that has been proven to be safe during pregnancy. Alcohol increases the risk of miscarriage and stillbirth. It also can cause fetal alcohol syndrome, which can result in the development of intellectual disabilities as well as facial deformities.
Smoking should also be avoided before, during, and after pregnancy, as smoking during any of these periods can negatively affect the baby, as well as the mother. Smoking during pregnancy can result in many detrimental health outcomes, including premature birth, fetal death, cesarean section (which can cause maternal hemorrhage), and more. It has also been found to increase the risk of sudden infant death syndrome, birth defects such as altered brainstem development and lung structure as well as cerebral palsy. Some studies have further shown that smoking during pregnancy can increase the likelihood of the child being obese as a teen, and obesity has numerous undesirable implications for mortality and morbidity.
This is not an exhaustive list of all the foods that should be avoided during pregnancy, and if unsure, consult a medical professional. Generally, keeping yourself healthy while paying special attention to foods that are known to be beneficial or detrimental to babies, in particular, will give your baby a better chance of being healthy.
- Institute of Medicine. “Weight Gain During Pregnancy: Reexamining The Guidelines.“
- Mayo Clinic. “Pregnancy weight gain: What’s healthy?” https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/pregnancy-weight-gain/art-20044360?pg=1.