On this page
Recommended weight gain by pre-pregnancy BMI
| Pre-pregnancy BMI | Total gain, one baby | Per week, 2nd and 3rd trimester | Total gain, twins |
|---|---|---|---|
| Under 18.5 | 28–40 lb (12.7–18.1 kg) | 1–1.3 lb | No guideline |
| 18.5–24.9 | 25–35 lb (11.3–15.9 kg) | 0.8–1 lb | 37–54 lb (16.8–24.5 kg) |
| 25–29.9 | 15–25 lb (6.8–11.3 kg) | 0.5–0.7 lb | 31–50 lb (14.1–22.7 kg) |
| 30 and above | 11–20 lb (5.0–9.1 kg) | 0.4–0.6 lb | 25–42 lb (11.3–19.1 kg) |
Most of the gain comes in the second and third trimesters. In the first trimester, a total of about 1.1 to 4.4 lb (0.5 to 2 kg) is typical.1
How to use your pre-pregnancy BMI
- Use your weight from just before pregnancy, or from your first prenatal visit if you don't know it.
- Calculate BMI as usual: weight in kg ÷ height in meters squared, or 703 × lb ÷ in². How to calculate BMI.
- Find your row in the table above.
- Track gain, not BMI. Compare the weight you've gained so far with the range for your week.
Why it matters
Gaining within the recommended range is linked with fewer complications.1 Gaining much more is linked with a higher chance of gestational diabetes, high blood pressure and a larger baby. Gaining much less is linked with a higher chance of a small baby and early birth.
Talk to your midwife or doctor before changing how much you eat during pregnancy, and mention it if your gain stays above or below your range for several weeks. Ranges are guides, not rules, and your provider may set a different goal. When to see a doctor.
Twins and more
The IOM gives provisional ranges for twins, shown above, but none for an underweight starting BMI or for triplets.1 Ask your provider for a personal goal in those cases.
Frequently asked questions
Can I calculate my BMI while pregnant?
You can, but the number isn't meaningful, because pregnancy weight includes the baby, placenta, fluid and extra blood. Use your pre-pregnancy BMI.
What if I'm gaining faster or slower than the range?
Weekly gain varies, and a single week off track isn't usually a concern. Mention a steady trend above or below the range at your next appointment.
Do these ranges apply outside the US?
The IOM (now the National Academy of Medicine) guidelines are widely used, but some countries have their own advice. Your local provider will know which applies.
Sources
This page is for education and is not medical advice. Your midwife, obstetrician or doctor can set a weight-gain goal that fits your health and pregnancy.
