BMI & Pregnancy Weight Gain Calculator
Calculate your pre-pregnancy BMI and track healthy weight gain during pregnancy
Calculate Pregnancy BMI & Weight Gain
Your weight before pregnancy
Your current weight during pregnancy
How many weeks pregnant you are
Healthy Pregnancy Weight Management
IOM Weight Gain Guidelines
| BMI Category | BMI Range | Single Pregnancy | Twin Pregnancy |
|---|---|---|---|
| Underweight | < 18.5 | 12.7-18.1 kg (28-40 lbs) | 22.7-28.1 kg (50-62 lbs) |
| Normal Weight | 18.5-24.9 | 11.3-15.9 kg (25-35 lbs) | 16.8-24.5 kg (37-54 lbs) |
| Overweight | 25-29.9 | 6.8-11.3 kg (15-25 lbs) | 14.1-22.7 kg (31-50 lbs) |
| Obese | ≥ 30 | 5.0-9.1 kg (11-20 lbs) | 11.3-19.1 kg (25-42 lbs) |
Guidelines from the Institute of Medicine (IOM) and National Research Council
BMI Categories
Based on World Health Organization standards
Weight Gain Timeline
First Trimester (0-12 weeks)
1-2 kg (2-4 lbs) total gain
Second Trimester (13-26 weeks)
Steady weekly gain begins
Third Trimester (27-40 weeks)
Continue steady weekly gain
Healthy Weight Benefits
Understanding BMI in Pregnancy
Why BMI Matters in Pregnancy
Pre-pregnancy BMI is a crucial indicator for determining healthy weight gain during pregnancy. It helps healthcare providers assess risks and provide personalized recommendations for optimal maternal and fetal outcomes.
Weight Gain Patterns
- •Most weight gain occurs in the 2nd and 3rd trimesters
- •Weekly gain should be steady and gradual
- •Individual variation is normal and expected
- •Quality of weight gain matters as much as quantity
Components of Weight Gain
Baby & Placenta (40%)
Baby, placenta, and amniotic fluid
Maternal Changes (35%)
Breast tissue, uterus, blood volume
Maternal Stores (25%)
Fat stores and fluid retention
Individual Needs: Some women may need modifications to standard guidelines based on medical conditions, age, or other factors.
Weight Gain Risks and Complications
Excessive Weight Gain Risks
Maternal Risks
- • Gestational diabetes
- • Preeclampsia and hypertension
- • Sleep apnea
- • Difficulty losing weight postpartum
- • Increased C-section risk
Fetal Risks
- • Macrosomia (large baby)
- • Birth injuries
- • Neural tube defects
- • Childhood obesity risk
Insufficient Weight Gain Risks
Maternal Risks
- • Nutritional deficiencies
- • Difficulty breastfeeding
- • Slower postpartum recovery
Fetal Risks
- • Low birth weight
- • Preterm delivery
- • Small for gestational age
- • Developmental delays
- • Increased neonatal mortality
Related Pregnancy Calculators
Medical Disclaimer
This calculator provides general guidance based on IOM recommendations and is not intended as medical advice. Individual weight gain needs may vary based on medical conditions, pre-existing health status, and other factors. Always consult with your healthcare provider for personalized recommendations and regular monitoring throughout pregnancy. If you have concerns about weight gain, eating disorders, or other health conditions, seek professional medical guidance immediately.