Pregnancy Weight Gain Calculator: Week-by-Week Targets
A woman with a pre-pregnancy BMI of 22 (normal weight) should gain 25-35 lbs total during pregnancy, with most weight gain in the second and third trimesters (~1 lb/week). By week 20, expect 8-12 lbs gained. By week 30, expect 18-25 lbs. Individual needs vary — consult your OB-GYN.
Pregnancy Weight Gain Calculator
Based on IOM 2009 guidelines.
Recommended Total Gain
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IOM Recommended Total Weight Gain
| Pre-Pregnancy BMI | Category | Singleton | Twins | |||
|---|---|---|---|---|---|---|
| Below 18.5 | Underweight | 28-40 lbs | 50-62 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 | Where Does the Weight Go? | Component | Weight at Term |
| Baby | 6-8 lbs | |||||
| Placenta | 1.5-2 lbs | |||||
| Amniotic fluid | 2 lbs | |||||
| Uterus growth | 2 lbs | |||||
| Breast tissue | 1-2 lbs | |||||
| Blood volume increase | 3-4 lbs | |||||
| Fluid retention | 3-4 lbs | |||||
| Fat stores (energy for breastfeeding) | 6-8 lbs | |||||
| Total | 25-35 lbs (normal BMI) |
Trimester-by-Trimester Guide
First trimester (weeks 1-13): Minimal weight gain expected — 1-4 lbs total. Some women lose weight due to morning sickness. Second trimester (weeks 14-27): Steady gain of 0.8-1 lb per week (normal BMI). Total: 12-14 lbs. Third trimester (weeks 28-40): Continued gain of 0.8-1 lb per week, then may plateau in final 2 weeks. Total: 10-14 lbs.
Sources
Frequently Asked Questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. Normal weight (BMI 18.5-24.9): 25-35 lbs. Underweight (BMI <18.5): 28-40 lbs. Overweight (BMI 25-29.9): 15-25 lbs. Obese (BMI 30+): 11-20 lbs. These are IOM guidelines for singleton pregnancies. Your OB-GYN may adjust these based on your individual health profile.
Is it safe to lose weight during pregnancy?
Intentional weight loss during pregnancy is generally not recommended. However, for women with BMI over 30, some recent research suggests modest weight loss or minimal gain in early pregnancy may be safe under close medical supervision. Never diet or restrict calories during pregnancy without your doctor's explicit guidance.
What if I am gaining too much weight?
Excessive weight gain increases risks of gestational diabetes, preeclampsia, and larger babies (macrosomia). Focus on nutrient-dense foods, regular physical activity (walking, swimming, prenatal yoga — with your doctor's approval), and appropriate portion sizes. Do not restrict calories. Discuss concerns with your OB-GYN at your next appointment.
When should I worry about weight gain in pregnancy?
Contact your healthcare provider if: you gain more than 6 lbs in one week (could indicate preeclampsia), you have not gained any weight by 20 weeks, you lose weight after the first trimester, or your total gain is significantly outside the IOM guidelines. Sudden changes are more concerning than gradual differences.
How many extra calories do I need during pregnancy?
First trimester: no additional calories needed. Second trimester: approximately 340 extra calories/day. Third trimester: approximately 450 extra calories/day. That is roughly one extra snack, not 'eating for two.' Focus on nutrient quality: additional protein (71g/day total), folate, iron, calcium, and DHA.