Donaldson R F Pregnancy Weight Gain Calculator
See the recommended weight gain range for your pregnancy, based on your pre-pregnancy BMI and the number of babies.
How this works
Your pre-pregnancy BMI (weight in kg ÷ height in metres squared) places you in a weight category: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9) or obesity (30 or above). The guidelines give a recommended total gain range and a weekly rate for each category. Gain in the first trimester is expected to be small (about 0.5–2 kg / 1–4.5 lb); the weekly rates apply from the second trimester. The “expected range so far” is an estimate that spreads the recommended gain evenly between the end of the first trimester and week 40, so it is only a rough guide — real gain is uneven and varies a lot between healthy pregnancies.
Source and limits
Ranges are from Weight Gain During Pregnancy: Reexamining the Guidelines, Institute of Medicine (now the National Academies of Sciences, Engineering, and Medicine), National Academies Press, 2009 — full report. The twin ranges are labelled “provisional” by the IOM, and no recommendation is given for underweight women carrying twins. The guidelines are for women pregnant with one or two babies and may not fit teenagers, short women or people with certain conditions. Your provider may recommend a different target for you.