Key Findings: Diabetes before pregnancy and congenital heart defects

In a new CDC study published in the American Journal of Preventive Medicine, researchers found that if women with type 1 or type 2 diabetes had their blood sugar in control before they became pregnant, about 2,670 babies could be born without congenital heart defects (CHDs) each year. The estimated number of individual types of CHDs that could be prevented varied, ranging from about 75 babies with hypoplastic left heart syndrome to 435 babies with an atrioventricular septal defect. In order to reduce the risk for heart defects among babies born to women with diabetes, it is important for women with diabetes to plan their pregnancies, receive proper health care, and work to get their diabetes under control prior to pregnancy. You can read an abstract of the article here .

Main Findings

Women with diabetes before pregnancy were about 4 times more likely to have a pregnancy affected by a CHD compared to women without diabetes.
Researchers estimated that about 8% of CHDs that occur each year were due to having diabetes that was not well-controlled before and early in pregnancy. Based on the number of babies born with a CHD in the United States each year, that estimate reflects about 2,670 babies each year whose CHD is a result of their mothers’ diabetes.
Diabetes before and early in pregnancy increased the risk for some CHDs more than others. For example, almost 24% of atrioventricular septal defects among babies in the United States were likely related to uncontrolled diabetes before and early in pregnancy. On the other hand, about 8% of coarctations of the aorta were related to diabetes before and early in pregnancy.

About Congenital Heart Defects (CHDs)

CHDs are the most common type of birth defect, affecting nearly 1% of all babies born in the United States1.
The causes of most CHDs are unknown. Some CHDs are caused by changes in a baby’s genes or chromosomes. Other causes might be combinations of genes and other factors, such as maternal obesity2, maternal smoking during pregnancy3, environmental risks, or maternal medication use.
Poor control of diabetes during pregnancy increases the chance of many birth defects, including CHDs4. Making sure that women receive proper health care before pregnancy can help prevent CHDs and other dangerous pregnancy complications.

About this Study

The aim of this study was to estimate how many total CHDs and individual types of CHD could be prevented by making sure that mothers with diabetes had good health before they became pregnant.
Researchers reviewed a number of studies that looked at the risk of CHDs among women with and without diabetes before pregnancy. Researchers used data from these studies to estimate the link between diabetes before pregnancy and all CHD, as well as diabetes before pregnancy and specific CHDs. Then they used this information to estimate how many CHDs could be prevented each year.
Good blood sugar control prior to pregnancy reduces the risk of birth defects among women with diabetes to almost the same level of risk as those women without diabetes. When calculating their estimates, the authors assumed that controlling diabetes before pregnancy completely eliminated the risk of CHDs due to diabetes.

CDC’s Activities: Congenital Heart Defects

CDC is working to understand more about the causes and health impact of congenital heart defects with the following activities:

Surveillance or disease tracking:
1. State programs: CDC funds and coordinates the Metropolitan Atlanta Congenital Defects Program (MACDP). CDC also funds 14 population-based state tracking programs. Birth defects tracking systems are vital to help us find out where and when birth defects occur and whom they affect.
2. Adolescents and adults: CDC recently started 3 projects to track congenital heart defects among adolescents and adults in order to learn about their health issues and needs across the lifespan.
Research: CDC funds the Centers for Birth Defects Research and Prevention, which collaborate on large studies such as the National Birth Defects Prevention Study (births 1997-2011) and the Birth Defects Study To Evaluate Pregnancy exposureS (beginning with births in 2014). These studies are working to identify factors that put babies at risk for birth defects, including heart defects.
Collaboration: CDC provides technical assistance to the Congenital Heart Public Health Consortium , a unique collaboration that brings together families, experts, and organizations to address congenital heart defects.

More Information

To learn more about congenital heart defects, please visit http://www.cdc.gov/heartdefects/.

To learn more about diabetes and birth defects, please visit http://www.cdc.gov/ncbddd/folicacid/features/folicacid-and-diabetes.html.

For more information about diabetes, please visit http://www.cdc.gov/diabetes/.

Key Findings Reference

Simeone RM, Devine OJ, Marcinkevage JA, Gilboa SM, Razzaghi H, Bardenheier BH, Sharma AJ, Honein MA. Diabetes and congenital heart defects: a systematic review, meta-analysis, and modeling project. AJPM: 2014. [epub ahead of date].

Additional References

Reller MD, Strickland MJ, Riehle-Colarusso T, Mahle WT, Correa A. Prevalence of congenital heart defects in metropolitan Atlanta, 1998-2005. J Pediatr 2008;153(6):807-13.
Gilboa SM, Correa A, Botto LD, Rasmussen SA, Waller DK, Hobbs CA, Cleves MA, Riehle-Colarusso TJ; National Birth Defects Prevention Study. Association between prepregnancy body mass index and congenital heart defects. Am J Obstet Gynecol. 2010;202(1):51.e1-51.e10.
Malik S, Cleves MA, Honein MA, Romitti PA, Botto LD, Yang S, Hobbs CA; National Birth Defects Prevention Study. Maternal smoking and congenital heart defects. Pediatrics. 2008;121(4):e810-6.
Correa A, Gilboa SM, Besser LM, Botto LD, Moore CA, Hobbs CA, Cleves MA, Riehle-Colarusso TJ, Waller DK, Reece EA. Diabetes mellitus and birth defects. Am J Obstet Gynecol. 2008 Sep;199(3):237.e1-9.