Estimate recommended pregnancy weight gain based on pre-pregnancy BMI, height, current week and twin status.
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.
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, 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.
| Prepregnancy BMI (kg/m²) | Category | Total Weight Gain Range (Single) | Total Weight Gain Range (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.
| Component | Typical Weight |
|---|---|
| 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 |
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).
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. Good food sources include leafy green vegetables, citrus fruits, dried beans and peas.
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. Found in dairy products, spinach, salmon, broccoli and kale.
Like calcium, vitamin D helps promote bone strength while also building the baby's bones and teeth. Found in fortified milk, orange juice, fish and eggs.
Protein is highly important for the growth of the baby throughout pregnancy. Good sources include lean meat, poultry, fish, eggs, beans, peas, nuts and soy products.
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. Iron deficiency anemia can result in fatigue and increase the risk of premature birth.
All recommendations are based on Institute of Medicine guidelines for average singleton and twin pregnancies. Individual weight gain needs vary based on many factors including age, activity level, pre-existing health conditions and specific pregnancy complications. This calculator is for informational purposes only and does not constitute medical advice. Always consult with your obstetrician or a registered dietitian for personalized weight gain guidance and prenatal care.
1. Institute of Medicine. 2009. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press.
2. Mayo Clinic. "Pregnancy nutrition: Foods to avoid during pregnancy."