How much weight gain is considered healthy during pregnancy
Healthy weight gain during pregnancy isn't a single universal number — it depends on your weight before becoming pregnant, captured here through pre-pregnancy BMI. This calculator uses the Institute of Medicine (IOM) guidelines, widely referenced by obstetric practitioners internationally.
The guidelines recommend a larger total gain for people starting at a lower BMI — roughly 12.5 to 18kg for underweight starting points — down to a smaller recommended gain of roughly 5 to 9kg for people starting at a higher BMI. The logic is that someone starting with fewer energy reserves benefits more from additional gain to support healthy fetal development, while someone starting with more reserves needs comparatively less.
Why the rate of gain matters too
Total gain matters, but so does pacing. Most of the recommended weight gain happens during the second and third trimesters, with a much smaller amount — often just a kilogram or two — expected in the first trimester. A roughly steady weekly gain through the remaining two trimesters is generally considered a healthy pattern, rather than gaining the bulk of the total very early or very late.
Why individual guidance still matters
These ranges are population guidelines, not individualized medical advice. Multiple pregnancies, pre-existing health conditions, and other personal factors can shift what's appropriate for any specific person — which is why ongoing conversations with a healthcare provider remain the most reliable source of guidance throughout pregnancy.