Pregnancy Weight Gain Calculator
Calculate recommended pregnancy weight gain by BMI
How to Use
- Enter your pre-pregnancy weight and height
- Enter your current weight and pregnancy week
- Click calculate to see recommended weight gain
- View your status and compare to IOM guidelines
IOM Pregnancy Weight Gain Guidelines
The Institute of Medicine (IOM) provides evidence-based guidelines for healthy weight gain during pregnancy based on pre-pregnancy BMI. These recommendations help reduce risks of pregnancy complications and promote better outcomes for both mother and baby.
| Pre-Pregnancy BMI | BMI Range | Recommended Total Gain | 2nd/3rd Trimester Weekly Gain |
|---|---|---|---|
| Underweight | < 18.5 | 28-40 lbs (12.7-18 kg) | 1 lb (0.45 kg) |
| Normal Weight | 18.5-24.9 | 25-35 lbs (11.3-15.9 kg) | 1 lb (0.45 kg) |
| Overweight | 25-29.9 | 15-25 lbs (6.8-11.3 kg) | 0.6 lb (0.28 kg) |
| Obese | ≥ 30 | 11-20 lbs (5-9 kg) | 0.5 lb (0.23 kg) |
Weight Gain by Trimester
Weight gain during pregnancy is not linear. Most women gain 1-4 pounds during the first trimester, then gain weight more steadily in the second and third trimesters.
- First Trimester (0-13 weeks): 1-4 lbs total gain. Some women lose weight due to morning sickness.
- Second Trimester (14-27 weeks): Steady weekly gain begins. Most women gain 12-14 lbs during this trimester.
- Third Trimester (28-40 weeks): Continued steady gain. Rate may slow in final weeks before delivery.
Factors Affecting Weight Gain
Several factors influence healthy pregnancy weight gain:
- Pre-pregnancy BMI: Higher BMI requires less weight gain
- Multiple pregnancy: Twins/multiples require additional weight gain (37-54 lbs for twins)
- Age: Younger mothers (especially teens) may need more weight
- Activity level: Active women may gain differently than sedentary women
- Morning sickness: May reduce first trimester gain
- Height: Taller women may gain more, shorter women less
Where Does Pregnancy Weight Go?
For a woman gaining 30 pounds during pregnancy, the weight is distributed approximately as:
| Component | Weight |
|---|---|
| Baby | 7-8 lbs |
| Placenta | 1-2 lbs |
| Amniotic fluid | 2 lbs |
| Uterus growth | 2 lbs |
| Breast tissue | 2 lbs |
| Blood volume increase | 3-4 lbs |
| Fluid retention | 2-3 lbs |
| Fat stores (for delivery/breastfeeding) | 6-8 lbs |
Risks of Inadequate or Excessive Gain
Both too little and too much weight gain can increase pregnancy risks:
Inadequate weight gain risks: Low birth weight baby, preterm delivery, developmental delays, difficulty breastfeeding.
Excessive weight gain risks: Gestational diabetes, high blood pressure, preeclampsia, cesarean delivery, large baby (macrosomia), difficulty losing weight postpartum, increased obesity risk for child.
Frequently Asked Questions
- How much weight should I gain during pregnancy?
- It depends on your pre-pregnancy BMI. Underweight women should gain 28-40 lbs, normal weight 25-35 lbs, overweight 15-25 lbs, and obese women 11-20 lbs. These are IOM guidelines for singleton pregnancies.
- Is it normal to lose weight in the first trimester?
- Yes, many women lose weight or maintain their weight in the first trimester due to morning sickness, nausea, and food aversions. As long as you start gaining appropriately in the second trimester and baby is growing well, this is usually not concerning.
- What if I'm gaining too much or too little weight?
- First, discuss with your healthcare provider. They can assess if adjustments are needed. Focus on nutrient-dense foods, appropriate portions, and safe physical activity. Don't attempt to diet or drastically change eating during pregnancy without medical supervision.
- How much extra should I eat during pregnancy?
- You don't need extra calories in the first trimester. In the second trimester, add about 340 calories per day. In the third trimester, add about 450 calories per day. Focus on quality nutrients, not just quantity of food.
- What about weight gain with twins or multiples?
- Women carrying twins should gain 37-54 lbs (normal weight BMI). Triplets or more require individualized guidance from your healthcare provider. Higher multiples need more weight gain to support healthy fetal growth.