Pregnancy Weight Gain Calculator
Track maternal weight gain against IOM 2009 guidelines. Features weekly targets based on pre-pregnancy BMI for a healthy pregnancy.
About
Gestational weight gain is a vital indicator of maternal and fetal health. This calculator serves as a maternity companion, comparing a user's current weight trajectory against the Institute of Medicine (IOM) 2009 guidelines. These standards vary significantly based on pre-pregnancy BMI. Insufficient gain can lead to preterm birth or low birth weight, while excessive gain increases the risk of gestational diabetes and postpartum retention. The tool maps the specific "safe tunnel" for weeks 1 through 40.
Formulas
The calculator first determines pre-pregnancy BMI to assign a category:
Recommended minimum weight Wmin at week t (for t > 13) is approximated by:
Where Ratemin is the weekly gain factor derived from the IOM table above.
Reference Data
| Pre-Pregnancy BMI | Category | Total Gain (lbs) | Total Gain (kg) | 2nd/3rd Trim. Rate (lbs/wk) |
|---|---|---|---|---|
| < 18.5 | Underweight | 28 - 40 | 12.5 - 18 | 1.0 - 1.3 |
| 18.5 - 24.9 | Normal Weight | 25 - 35 | 11.5 - 16 | 0.8 - 1.0 |
| 25.0 - 29.9 | Overweight | 15 - 25 | 7 - 11.5 | 0.5 - 0.7 |
| ≥ 30.0 | Obese | 11 - 20 | 5 - 9 | 0.4 - 0.6 |
| Twin Pregnancy | All | 37 - 54 | 17 - 25 | 1.5 (approx) |