Obese and Overweight Women Have a Higher Risk of Giving Birth to Baby with Heart Defects

The largest study of obesity during pregnancy and babies with heart defects in the United States finds that women who were overweight or obese before they became pregnant had an approximately 18 percent increased risk of having a baby with certain heart defects compared with women who were of normal body mass index (BMI) before they became pregnant. Severely obese women had approximately a 30 percent increased risk, according to a study by the Centers for Disease Control and Prevention.

The study, "Association Between Prepregnancy Body Mass Index and Congenital Heart Defects," published in the American Journal of Obstetrics and Gynecology, found a significant increase in several types of heart defects in babies born to overweight and obese women, compared to babies born to normal weight women. These included obstructive defects on the right side of the heart, and defects in the tissue that separates the two upper chambers of the heart.

Obesity and overweight were determined based on the study's participants' BMIs. A BMI is a measure of weight in relation to height. Overweight is defined as a BMI of 25-29.9, moderate obesity is defined as a BMI 30-34.9, and severe obesity is defined as a BMI of 35 or higher. For example, a woman who is 5 feet, 5 inches tall and weighs 190 pounds has a BMI of 31.6 which places her in the moderate obesity category; a woman of that same height who weighs 160 pounds has a BMI of 26.6 which places her in the overweight category.

"Congenital heart defects are the most common types of birth defect, and among all birth defects, they are a leading cause of illness, death, and medical expenditures," said Dr. Edwin Trevathan, director of the CDC's National Center on Birth Defects and Developmental Disabilities. "Women who are obese and who are planning a pregnancy could benefit by working with their physicians to achieve a healthy weight before pregnancy."

The study looked at 25 types of heart defects and found associations with obesity for 10 of them. Five of these 10 types were also associated with being overweight before pregnancy. Women who were overweight but not obese had approximately a 15 percent increased risk of delivering a baby with certain heart defects.

The study accounted for several important factors such as maternal age and race–ethnicity. Mothers with type 1 or 2 diabetes before they got pregnant, a strong risk factor for heart defects, were excluded from the study.

"These results support previous studies, as well as provide additional evidence, that there is an association between a woman being overweight or obese before pregnancy and certain types of heart defects," said Suzanne Gilboa, epidemiologist at CDC's National Center on Birth Defects and Developmental Disabilities, and primary author of the study. “This provides another reason for women to maintain a healthy weight. In addition to the impact on a woman's own health and the known pregnancy complications associated with maternal obesity, the baby's health could be at risk."

One important limitation of the study is that BMI is calculated based on self–reported weight and height, and weight may be underreported by women during the study interview. Although the study found an association between overweight and obesity and the risk of certain birth defects, further study is needed to determine whether body weight is the direct cause of these birth defects.

The analysis included 6,440 infants with congenital heart defects and 5,673 infants without birth defects whose mothers were interviewed as part of the National Birth Defects Prevention Study (NBDPS). The NBDPS is funded by the CDC to collect information from mothers of children with and without birth defects in Arkansas, California, Georgia, Iowa, Massachusetts, New York, North Carolina, Texas, and Utah. This study is the largest effort ever undertaken in the United States to identify risk factors for birth defects.

For more information about heart and other birth defects please call toll free 1-800-CDC-INFO or visit http://www.cdc.gov/ncbddd.

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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES