Pregnancy Articles

BMI, Weight Gain and Pregnancy: An Explanation

How is Your Recommended Weight Gain Calculated?

Thirty to 40 years ago, most pregnant women were given the same weight gain advice: gain approximately 15 pounds. This was in an effort to prevent pregnancy complications and retention of excess weight after delivery. However in the past several decades, obesity has become an epidemic in the United States, and today, 33% of American women are obese. For women of childbearing age, obesity is of particular concern due to the increase in complications for mom and for baby.

According to the American College of Obstetricians and Gynecologists, there are significant risks associated with obesity and pregnancy. Obesity is a risk factor for miscarriage, and has been linked to an increased risk of gestational hypertension, preeclampsia, and gestational diabetes. As a woman's body mass index increases, so do her chances of needing a Caesarean delivery.

Therefore in 1990, the Institute of Medicine did a literature review and developed weight gain guidelines for pregnant women based on body mass index. BMI is a calculation that uses a person's height and weight to estimate how much body fat you have. Too much body fat can lead to illnesses and other health problems. Find a BMI calculator here. (Note that while measuring BMI is used to determine pregnancy weight gain, it is not accurate to use during pregnancy.)

These IOM guidelines abandoned the "one size fits all" pregnancy weight gain recommendation. Pregnancy weight gain should be based on a woman's height and pre-pregnancy weight, thus improving the pregnancy outcome for mom and baby. Such tailored recommendations decrease the risk of excessive postpartum weight retention, low birth weight infant, large birth weight infant, and reduce an infant's risk of chronic disease as an adult.

A few years later, the Maternal and Child Health Bureau of the U.S. Department of Health and Human Services began to address concerns about weight gain during pregnancy. In 1998, the National Heart, Lung, and Blood Institute released its own pregnancy weight gain classification using BMI. This classification differed slightly from the 1990 IOM criteria.

Pregnancy BMI and Weight Gain Ranges


IOM 1990 Body Mass Index

NHLBI 1998 Body Mass Index

Pregnancy Weight Gain


< 19.8


28-40 pounds

Normal Weight



25-35 pounds




15-25 pounds



30 and greater

no more than 15 pounds

Therefore, you may notice slight differences in the BMI categories as you gather resources from BabyFit, read pregnancy magazines, and talk to your doctor. As always, it is best to follow the advice of your health care provider about appropriate and healthy pregnancy weight gain for your particular medical needs.

Weight gain during pregnancy and the impact on the health of mother and infant are important topics, and research is constantly updated. Experts anticipate new guidelines will be released in the near future. BabyFit follows this topic closely and updates the site with the most current recommendations as they are made available.
Page 1 of 1  

About The Author

Becky Hand
Becky is a registered and licensed dietitian with almost 20 years of experience. She teaches prenatal classes and counsels individuals, helping women eat right and stay fit before, during and after their pregnancies.
Becky Hand

Member Comments

There are currently no comments on this article