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Pregnancy Weight Gain Calculator
The weight gain the IOM recommends for your pre-pregnancy BMI, in total and by this week.
Result…
How it's calculated
Pre-pregnancy BMI = kg ÷ m² IOM 2009 total gain (one baby): under 18.5 → 12.5–18 kg · 18.5–24.9 → 11.5–16 kg · 25–29.9 → 7–11.5 kg · 30+ → 5–9 kg Twins: 17–25, 14–23, 11–19 kg By week: 0.5–2 kg over weeks 1–13, then 0.44–0.58 / 0.35–0.50 / 0.23–0.33 / 0.17–0.27 kg a week
The Institute of Medicine (now the National Academy of Medicine) set these ranges in 2009 from outcomes for mother and baby. Gain is small in the first trimester and steadier after. The week-by-week range is a smooth guide built from the IOM rates; gain is rarely perfectly even, and twin weekly rates are not set out in the same detail.
Your numbers, step by step
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