Pregnancy Weight Gain Calculator
Get personalized gestational weight gain recommendations based on your pre-pregnancy BMI, following Institute of Medicine guidelines.
How Much Weight Should You Gain During Pregnancy?
The Institute of Medicine (IOM) — now the National Academy of Medicine — published updated gestational weight gain guidelines in 2009. These evidence-based recommendations are based on pre-pregnancy BMI and are associated with the best outcomes for both mother and baby, including reduced risk of cesarean delivery, gestational diabetes, large-for-gestational-age infants, and postpartum weight retention.
IOM Recommended Total Gestational Weight Gain
| Pre-Pregnancy BMI | Category | Recommended Total Gain | 2nd/3rd Tri Rate (lbs/week) |
|---|---|---|---|
| Below 18.5 | Underweight | 28–40 lbs | 1 (1–1.3) lbs/week |
| 18.5–24.9 | Normal weight | 25–35 lbs | 1 (0.8–1) lbs/week |
| 25.0–29.9 | Overweight | 15–25 lbs | 0.6 (0.5–0.7) lbs/week |
| 30.0+ | Obese | 11–20 lbs | 0.5 (0.4–0.6) lbs/week |
| (twins) | Normal weight | 37–54 lbs | 1.5 lbs/week |
Where Does Pregnancy Weight Go?
Of a typical 25–35 lb gain for a normal-weight woman, approximately: Baby: 7.5 lbs; Placenta: 1.5 lbs; Amniotic fluid: 2 lbs; Uterus: 2 lbs; Breast tissue: 2 lbs; Blood volume increase: 3–4 lbs; Fluid retention: 2–3 lbs; Fat and protein stores: 6–8 lbs.
Weight Gain Pattern by Trimester
First trimester: 1–4 lbs total (morning sickness may limit gain). Second trimester: ~1 lb/week. Third trimester: ~1 lb/week. The majority of weight gain occurs in the second and third trimesters during rapid fetal growth.