Pregnancy weight gain references (IOM 2009)
Enter your height, your weight before pregnancy and the current week. The tool shows the gain range published by the Institute of Medicine (IOM, 2009). These are references to discuss with your care team, never a diet.
General information, not medical advice. This result does not replace a doctor. If in doubt or if you have symptoms, see a health professional.
Result
11.5 – 16Reference total gain (kg)
- BMI before pregnancy
- 22
- IOM group: starting BMI 18.5 to 24.9.
- Reference at this week (kg)
- 5 – 7.7
- Current gain (kg)
- 6
- Your gain is within the reference for this week.
- Reference rate in the 2nd and 3rd trimesters (kg per week)
- 0.35 – 0.5
- During pregnancy, never start a diet or any restriction without medical advice.
Inputs
- Height
- 165
- Weight before pregnancy
- 60
- Week of pregnancy
- 24
- Current weight (optional)
- 66
- Pregnancy
- One baby
How it is calculated
Pre-pregnancy BMI = weight ÷ (height in m)². IOM total ranges: below 18.5 → 12.5 to 18 kg; 18.5 to 24.9 → 11.5 to 16 kg; 25 to 29.9 → 7 to 11.5 kg; 30 or more → 5 to 9 kg.
Result
Reference total gain (kg)
- BMI before pregnancy
- 22
- Reference at this week (kg)
- 5 – 7.7
- Current gain (kg)
- 6
How it is calculated
- Pre-pregnancy BMI = weight ÷ (height in m)². IOM total ranges: below 18.5 → 12.5 to 18 kg; 18.5 to 24.9 → 11.5 to 16 kg; 25 to 29.9 → 7 to 11.5 kg; 30 or more → 5 to 9 kg.
- Reference at a week: from 0 to 0.5-2 kg at the end of the first trimester (13 weeks), then a straight line to the total range at 40 weeks.
- Twins: IOM provisional ranges (17 to 25 kg, 14 to 23 kg, 11 to 19 kg), with no weekly reference.
Example
165 cm, 60 kg before pregnancy (BMI 22.0), 24 weeks, 66 kg today: total range 11.5 to 16 kg; reference at 24 weeks 5 to 7.7 kg; current gain 6.0 kg, within the reference.
Good to know
- US population references: other countries use other guidance. Medical review is advised before any personal use.
- The weekly reference is a linear simplification; real weight gain is not steady.
- Does not apply to pregnant teenagers or particular medical situations. Pregnancy care belongs to a midwife or doctor.
Sources
- Institute of Medicine (IOM) and National Research Council, Weight Gain During Pregnancy: Reexamining the Guidelines, 2009
Frequently asked questions
What is this tool used for?
Enter your height, your weight before pregnancy and the current week. The tool shows the gain range published by the Institute of Medicine (IOM, 2009). These are references to discuss with your care team, never a diet.
How is the result calculated?
Pre-pregnancy BMI = weight ÷ (height in m)². IOM total ranges: below 18.5 → 12.5 to 18 kg; 18.5 to 24.9 → 11.5 to 16 kg; 25 to 29.9 → 7 to 11.5 kg; 30 or more → 5 to 9 kg.
What should I check before using the result?
US population references: other countries use other guidance. Medical review is advised before any personal use.