Pregnancy Weight Gain Calculator
Track your recommended pregnancy weight gain by week based on IOM guidelines. Enter your pre-pregnancy weight, height, and current gestational week.
Quick Answer
The Institute of Medicine recommends 25-35 lbs total gain for normal-weight women, 28-40 lbs for underweight, 15-25 lbs for overweight, and 11-20 lbs for obese. Most gain occurs in the 2nd and 3rd trimesters at a rate of 0.5-1.3 lbs per week depending on BMI category.
Enter to compare your actual gain to the recommended range
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Your weight gain is within the recommended range.
Week-by-Week Recommended Gain
| Week | Low (lbs) | High (lbs) | Trimester |
|---|---|---|---|
| 1 | 0.1 | 0.3 | 1st |
| 3 | 0.3 | 1 | 1st |
| 5 | 0.4 | 1.7 | 1st |
| 7 | 0.6 | 2.4 | 1st |
| 9 | 0.8 | 3 | 1st |
| 11 | 0.9 | 3.7 | 1st |
| 13 | 1.1 | 4.4 | 1st |
| 15 | 2.7 | 6.4 | 2nd |
| 17 | 4.3 | 8.4 | 2nd |
| 19 | 5.9 | 10.4 | 2nd |
| 20 ← | 6.7 | 11.4 | 2nd |
| 21 | 7.5 | 12.4 | 2nd |
| 23 | 9.1 | 14.4 | 2nd |
| 25 | 10.7 | 16.4 | 2nd |
| 27 | 12.3 | 18.4 | 3rd |
| 29 | 13.9 | 20.4 | 3rd |
| 31 | 15.5 | 22.4 | 3rd |
| 33 | 17.1 | 24.4 | 3rd |
| 35 | 18.7 | 26.4 | 3rd |
| 37 | 20.3 | 28.4 | 3rd |
| 39 | 21.9 | 30.4 | 3rd |
IOM Guidelines by BMI Category
About This Tool
Pregnancy weight gain is one of the most closely monitored metrics in prenatal care, and for good reason — both too little and too much weight gain during pregnancy are associated with complications for mother and baby. The Institute of Medicine (IOM, now the National Academy of Medicine) published its current guidelines in 2009, establishing recommended total weight gain ranges based on pre-pregnancy Body Mass Index (BMI). These guidelines remain the standard used by obstetricians and midwives across the United States.
The IOM recommendations are designed to optimize outcomes for both maternal and fetal health. For normal-weight women (BMI 18.5-24.9), the recommended total gain is 25-35 pounds. Underweight women (BMI below 18.5) should gain 28-40 pounds. Overweight women (BMI 25-29.9) should gain 15-25 pounds. Women with obesity (BMI 30+) should gain 11-20 pounds. These ranges account for the weight of the baby, placenta, amniotic fluid, increased blood volume, breast tissue growth, uterine enlargement, and maternal fat stores needed for breastfeeding.
Weight Gain by Trimester
Weight gain during pregnancy is not evenly distributed across all 40 weeks. The first trimester (weeks 1-13) typically involves minimal weight gain — roughly 1 to 4.4 pounds total. Some women actually lose weight in the first trimester due to morning sickness. The second and third trimesters are when the majority of weight gain occurs, at a rate that depends on pre-pregnancy BMI. Normal-weight women should gain approximately 0.8-1.0 pounds per week during the second and third trimesters. Overweight women should gain 0.5-0.7 pounds per week, and women with obesity should gain 0.4-0.6 pounds per week.
Where the Weight Goes
A 30-pound weight gain during pregnancy is distributed approximately as follows: baby accounts for 7.5 pounds, the placenta accounts for 1.5 pounds, amniotic fluid adds 2 pounds, uterine growth adds 2 pounds, increased breast tissue adds 2 pounds, increased blood volume adds 4 pounds, extra fluid in tissues adds 4 pounds, and maternal fat stores add 7 pounds. These fat stores serve as an energy reserve for breastfeeding after delivery. Understanding this breakdown helps explain why the recommended gain is well above the baby's birth weight alone.
Risks of Inadequate Weight Gain
Gaining too little weight during pregnancy increases the risk of preterm birth, low birth weight (under 5.5 pounds), and small-for-gestational-age infants. Low birth weight is associated with increased neonatal morbidity and developmental complications. Inadequate gain may also indicate nutritional deficiencies that affect fetal brain development, bone growth, and organ maturation. Women who are underweight before pregnancy and fail to gain adequately face the highest risk for these complications.
Risks of Excessive Weight Gain
Excessive weight gain increases the risk of gestational diabetes, preeclampsia, cesarean delivery, macrosomia (baby weighing over 8.8 pounds), birth injuries, and postpartum weight retention. Women who gain significantly more than the recommended amount are more likely to retain excess weight after delivery, which increases the risk of obesity, type 2 diabetes, and cardiovascular disease long-term. Excessive gain also increases the child's risk of childhood obesity, creating an intergenerational cycle. A 2015 study in the American Journal of Obstetrics and Gynecology found that approximately 47% of American women gain more than the IOM recommendation, while 21% gain less.
Monitoring and Adjustments
Weight should be monitored at each prenatal visit, typically monthly in the first and second trimesters and every two weeks in the third trimester. A sudden increase in weight gain (more than 2 pounds in a week) may indicate fluid retention and should be evaluated for preeclampsia. Conversely, weight loss or failure to gain in the second or third trimester warrants investigation for nutritional issues or fetal growth problems. The IOM guidelines are population-level recommendations — individual circumstances including age, height, multiple gestation (twins gain 37-54 pounds recommended), and medical conditions may require adjustments that only your healthcare provider can make.