Weight Gain in Pregnancy

Weight gain in pregnancy

In 2009, the Institute of Medicine published guidelines on weight gain through pregnancy based on BMI (basal metabolic index) calculated using the pre-pregnancy height and weight. This at least gives women a rough idea of where they should be by the end of pregnancy. 1

Additionally, they created a website with common questions and answers women ask about weight gain in pregnancy including how much to gain, how to distribute it over the course of a pregnancy, how weight gain affects pregnancy, etc.

The American College of Obstetricians & Gynecologists published guidance on this topic in 2020. They caution that while these guidelines are reasonable for those whose BMI fall in the categories with BMI < 18.5 and those in the 18.5-24.9 range, that those in the categories above a BMI of 25 may benefit from a smaller weight gain in pregnancy. See what they had to say below. 2

BMI 25.0-24.9

“Gestational weight gain below the IOM recommendations among overweight pregnant women does not appear to have a negative effect on fetal growth or neonatal outcomes. In several studies, overweight women who gained 2.7–6.4 kg (6–14 lb) had similar fetal growth, perinatal and neonatal outcomes, and less postpartum weight retention as overweight women who gained weight within the currently recommended IOM range 3 4 5 6 7 8. For the overweight pregnant woman who is gaining less than the recommended amount but has an appropriately growing fetus, no evidence exists that encouraging increased weight gain to conform with the current IOM guidelines will improve maternal or fetal outcomes.”2

BMI >30

“For an obese pregnant woman who is gaining less weight than recommended but has an appropriately growing fetus, no evidence exists that encouraging increased weight gain to conform with the updated IOM guidelines will improve maternal or fetal outcomes.”2

How to use the IOM Chart

  1. Start by calculating pre pregnancy BMI https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html
  2. Then refer to the chart for single pregnancies
  3. Most importantly, talk to your health care provider and make sure this makes sense for you and your current pregnancy because each pregnancy and each patient is unique.

Institute of Medicine Weight Gain Recommendations For Women Pregnant With One Baby

BMI less than 18.5

28-40 pounds

Normal Weight
BMI 18.5-24.9

25-35 pounds

BMI 25.0-29.9

15-25 pounds

BMI greater than or equal to 30.0

11- 20 pounds


More Resources:

CDC Reproductive Health:


Institute of Medicine Site on Weight Gain in Pregnancy:



  1. Rasmussen KM, Yaktine AL, editors. Institute of Medicine (Committee to Reexamine IOM Pregnancy Weight Guidelines, Food and Nutrition Board and Board on Children, Youth, and Families) Weight Gain During Pregnancy: Reexamining the Guidelines. Washington, DC: National Academy Press; 2009. Provides new guidelines for weight gain during pregnancy that are based

on minimizing the risks of inadequate or excessive gains to mothers as well as their infants.


  1. Weight gain during pregnancy. Committee Opinion No. 548. American College of Obstetricians and Gynecologists. Obstet Gynecol 2013;121:210–2.
Sarah Belliotti, MD

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