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About this tool
Total and weekly pregnancy weight gain ranges from your pre-pregnancy BMI, using the IOM guideline bands for singletons and twins.
Recommended pregnancy weight gain is set by the BMI you had before conceiving, and this calculator applies the Institute of Medicine (2009) bands that ACOG and most antenatal services still use: 12.5–18 kg for underweight, 11.5–16 kg for a healthy BMI, 7–11.5 kg for overweight and 5–9 kg for obese. It also gives the weekly rate for the second and third trimesters and shows where your gain should be by the week you are in now. Twin ranges are included where the IOM issued them.
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Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Four BMI categories with their published total ranges, not one average number.
Splits the small first-trimester allowance from the steady weekly rate that follows.
Applies the IOM provisional twin ranges and says plainly where no range exists.
For a singleton pregnancy the IOM ranges are 12.5–18 kg if your pre-pregnancy BMI was under 18.5, 11.5–16 kg for BMI 18.5–24.9, 7–11.5 kg for BMI 25–29.9 and 5–9 kg for BMI 30 or more. These are population guidelines — your own target may differ and should come from your obstetrician.
Only about 0.5 to 2 kg in total across the first 13 weeks, for every BMI category. Nausea means some people lose weight instead, which is usually not a concern on its own but is worth mentioning at your next appointment.
About 0.51 kg a week if you started underweight, 0.42 kg at a healthy BMI, 0.28 kg if overweight and 0.22 kg if obese. Week-to-week weight swings of half a kilogram are normal, so judge the trend over a few weeks rather than a single weighing.
Gaining outside the range is associated with higher rates of large- or small-for-gestational-age babies, but a single reading rarely means much — fluid retention, illness and scale differences all shift it. Raise a persistent trend with your midwife or obstetrician rather than restricting food during pregnancy on your own.
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