Sky Strike 3DPlayPregnancy Weight Gain
See the Institute of Medicine total-gain range for your pre-pregnancy BMI, and how much weight has changed so far.
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Medical disclaimer. This page is general education for adults. It does not diagnose pregnancy, anemia, dehydration, or menopause, and it does not replace a clinician, midwife, or dietitian. Get in-person care for heavy bleeding, fainting, chest pain, a severe headache, or a baby who is hard to wake. Read the disclaimer before changing food, supplements, or feeding.
How to use: Enter height, weight before pregnancy, and weight now. Add weeks if you want the week-by-week arithmetic from the same table.
The numbers on this page come from one report: Institute of Medicine and National Research Council, Weight Gain During Pregnancy: Reexamining the Guidelines, published by the National Academies Press in 2009. Table S-1 sets a total gain range from pre-pregnancy body mass index, using World Health Organization BMI cuts. Underweight is a BMI under 18.5, and the singleton range is 28–40 lb (12.5–18 kg). Normal weight is 18.5–24.9, and the range is 25–35 lb (11.5–16 kg). Overweight is 25.0–29.9, and the range is 15–25 lb (7–11.5 kg). Obesity is a BMI of 30 or higher, and the range is 11–20 lb (5–9 kg). The American College of Obstetricians and Gynecologists still points clinicians to these ranges.
The same table publishes a rate for the second and third trimesters. Underweight is a mean of 0.51 kg per week (range 0.44–0.58). Normal weight is 0.42 kg per week (0.35–0.50). Overweight is 0.28 kg per week (0.23–0.33). Obesity is 0.22 kg per week (0.17–0.27). In pounds, the means are about 1, 1, 0.6, and 0.5 lb per week. The footnote on the table says the weekly rates assume a first-trimester gain of 0.5–2 kg (1.1–4.4 lb). If you type a week after week 13, this page adds that published weekly range onto that first-trimester assumption. The product is arithmetic from the table. It is not a second guideline the committee wrote down as a week-by-week quota.
Twins have provisional totals in the same report, and only for some BMI groups. Normal weight is 37–54 lb (17–25 kg). Overweight is 31–50 lb (14–23 kg). Obesity is 25–42 lb (11–19 kg). The committee wrote that it did not have enough information for a provisional range for underweight women carrying twins. This page repeats that sentence and does not invent a range. It also does not invent a range for triplets or more. The report said the evidence was insufficient for higher-order pregnancies. The weekly rate is a singleton figure, so it is withheld when you select twins.
Gain so far is current weight minus pre-pregnancy weight. The comparison is with the full-pregnancy total, so a number under the range at week 16 is ordinary. The range is the destination the guideline describes, not a checkpoint for every visit. A number already above the total is worth taking to the next prenatal visit before any diet change. The report itself says the ranges should be used with clinical judgment, diet, and activity, and that a result outside the range should be read next to how the baby is growing. A webpage cannot do that reading.
BMI here is weight in kilograms divided by height in metres squared, then rounded to one decimal before the category is chosen, which is how a clinic chart usually prints BMI. Pounds convert with the factor 0.45359237 kilograms per pound, and inches convert with 2.54 centimetres. Type the measurements you have. Do not pre-round them and expect the same BMI. The BMI calculator on this site is the general adult tool. This page adds the pregnancy ranges on top of the same WHO categories.
Short stature and adolescence do not get a separate range. The 2009 committee withdrew the older advice to aim low for women under 157 cm, and it said pregnant adolescents should use the adult BMI cuts until better evidence exists. Pair the result with the week counter and the due date calculator if you are dating the pregnancy from the last period. Sudden swelling, a severe headache, bleeding, or a baby who is moving much less than usual needs a phone call to your own clinician or local emergency care. The iron and water page covers the published iron RDA in pregnancy, which is a different question from the scale.
Frequently asked questions
Which guideline is this?
Institute of Medicine and National Research Council, Weight Gain During Pregnancy: Reexamining the Guidelines (National Academies Press, 2009), Table S-1. BMI categories are the WHO cuts.
What is the range for a normal BMI with one baby?
25–35 pounds (11.5–16 kg) across pregnancy, with a second-and-third-trimester mean of 0.42 kg per week.
Why is there no range for underweight twins?
The 2009 report said the evidence was not enough for even a provisional range in that group. This page does not fill the gap.
Does a low gain at mid-pregnancy mean I am behind?
The published range is a total for the pregnancy. Being under that total before the last weeks is common. Ask your prenatal clinician how your own curve looks.
Are triplets included?
No. The report did not set a gain range for triplets or higher-order pregnancies.
Sources
- Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: National Academies Press, 2009. Table S-1, including the first-trimester assumption of 0.5–2 kg (1.1–4.4 lb).
- World Health Organization BMI categories: under 18.5, 18.5–24.9, 25.0–29.9, and 30 or higher, as adopted in that report.
- American College of Obstetricians and Gynecologists continues to point clinicians to these 2009 ranges.
