Pregnancy Weight Gain Calculator
Enter your pre-pregnancy weight, height, and current week to see the IOM-recommended weight gain range for your BMI category.
IOM Pregnancy Weight Gain Guidelines (Singleton Pregnancy)
| Pre-pregnancy BMI | Total Gain (lbs) | 2nd/3rd Tri Rate |
|---|---|---|
| Underweight (<18.5) | 28–40 lbs | 1.0–1.3 lbs/week |
| Normal (18.5–24.9) | 25–35 lbs | 0.8–1.0 lbs/week |
| Overweight (25–29.9) | 15–25 lbs | 0.5–0.7 lbs/week |
| Obese (≥30) | 11–20 lbs | 0.4–0.6 lbs/week |
Source: Institute of Medicine (IOM), 2009. First trimester: approximately 1–4 lbs total. Always consult your healthcare provider for personalized guidance.
Frequently Asked Questions
How much weight should I gain during pregnancy?
The Institute of Medicine (IOM) recommends different weight gain ranges based on pre-pregnancy BMI: Underweight (BMI <18.5): 28–40 lbs. Normal weight (BMI 18.5–24.9): 25–35 lbs. Overweight (BMI 25–29.9): 15–25 lbs. Obese (BMI ≥30): 11–20 lbs. For twin pregnancies, recommendations are higher: normal weight = 37–54 lbs. These are guidelines — your OB will set personalized targets based on your health history. Gaining within the recommended range reduces risks of gestational diabetes, C-section, and babies that are too large or small.
When do I gain the most weight in pregnancy?
Weight gain is not linear. First trimester (weeks 1–13): Most women gain only 1–5 lbs total. Morning sickness may cause weight loss in some. Second trimester (weeks 14–27): Weight gain accelerates — typically 0.5–1 lb per week. Baby grows rapidly; body is building blood volume and breast tissue. Third trimester (weeks 28–40): Weight gain continues at a similar rate; baby gains about 0.5 lbs/week in the final weeks. Much of the weight gained is not fat — it includes the baby (~7–8 lbs), placenta (~1.5 lbs), amniotic fluid (~2 lbs), increased blood and fluid (~8–10 lbs), uterus and breast tissue (~3–4 lbs).
Is it dangerous to gain too much weight during pregnancy?
Excessive gestational weight gain (above IOM recommendations) is associated with: gestational diabetes (25–45% increased risk), preeclampsia (high blood pressure), cesarean delivery (15–30% increased risk), large-for-gestational-age baby (macrosomia), difficulty losing weight postpartum, and increased childhood obesity risk for the baby. However, severe calorie restriction during pregnancy is also dangerous — the goal is to stay within the recommended range, not to diet. If you are gaining faster than recommended, focus on food quality rather than restriction.
How much weight do you lose after giving birth?
Most women lose 10–13 lbs immediately after delivery (baby, placenta, amniotic fluid, blood). Over the following weeks, retained fluid (another 5–8 lbs) is released. Breastfeeding supports postpartum weight loss — it burns approximately 300–500 extra calories per day. Most women return to pre-pregnancy weight within 6–12 months with healthy eating and gradual activity resumption. Women who gained within IOM recommendations lose weight more easily postpartum than those who gained excessively. Avoid intensive dieting while breastfeeding.