The Body Mass Index (BMI) "is moderately correlated with direct measures of body fat and is based on weight and height and calculated as kg / m^2."
"BMI values under 18.5 are classified as underweight; those from 18.5 to 24.9 are classified as normal or healthy weight; values from 25.0 to 29.9 are classified as overweight; and values of 30.0 and over are classified as obesity. Within the obesity category, BMI is further divided into three classes. Class I obesity includes BMI values from 30.0 to 34.9, Class II obesity includes values from 35.0 to 39.9, and Class III obesity includes BMI values of 40.0 and over."
Percentages in this graph were rounded.
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Rates of low birthweight among U.S. infants in 2020, by maternal prepregnancy BMI
In 2020, the share of infants with a low birthweight in the U.S. varied depending on the prepregnancy body mass index of the mother. Specifically, mothers who had a BMI correspondent to "underweight" had the highest rate of low infant birthweight, with 13.2 percent.
This graph shows the percentage of infants in the U.S. who were born with a low birthweight in 2020, by maternal prepregnancy body mass index (BMI).
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CDC. (December 28, 2021). Percentage of infants with a low birthweight in the United States in 2020, by maternal prepregnancy body mass index [Graph]. In ÌÇÐÄÆÆ½â°æ. Retrieved July 29, 2026, from /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/
CDC. "Percentage of infants with a low birthweight in the United States in 2020, by maternal prepregnancy body mass index." Chart. December 28, 2021. ÌÇÐÄÆÆ½â°æ. Accessed July 29, 2026. /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/
CDC. (2021). Percentage of infants with a low birthweight in the United States in 2020, by maternal prepregnancy body mass index. ÌÇÐÄÆÆ½â°æ. ÌÇÐÄÆÆ½â°æ Inc.. Accessed: July 29, 2026. /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/
CDC. "Percentage of Infants with a Low Birthweight in The United States in 2020, by Maternal Prepregnancy Body Mass Index." ÌÇÐÄÆÆ½â°æ, ÌÇÐÄÆÆ½â°æ Inc., 28 Dec 2021, /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/
CDC, Percentage of infants with a low birthweight in the United States in 2020, by maternal prepregnancy body mass index ÌÇÐÄÆÆ½â°æ, /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/ (last visited July 29, 2026)
Percentage of infants with a low birthweight in the United States in 2020, by maternal prepregnancy body mass index [Graph], CDC, December 28, 2021. [Online]. Available: /statistics/1309803/low-birthweight-infants-by-maternal-prepregnancy-bmi-us/