Maternal diabetes can develop during pregnancy, affect how a body's cells use sugar, and cause high blood sugar levels that can affect a pregnancy and a baby's health. When poorly controlled, it is a well-known, established teratogen, a factor that causes an embryo or fetus to develop abnormally. It causes heart defects but also other major birth defects, 1-10, i.e. infants with two or more major malformations, or three or more minor malformations. With good blood sugar control, including monitoring and controlling blood sugar levels starting before becoming pregnant, diabetes-related malformations can be minimized and possibly eliminated. Because some women have diabetes but do not know it, screening for unrecognized diabetes before conception is important for detecting and controlling diabetes and its teratogenic effects in pregnancy.
Maternal diabetes has been associated with a wide range of congenital heart defects. Specific types of heart defects consistently associated with maternal diabetes include laterality defects (heterotaxy) and several conotruncal defects. Less consistently, but still associated with maternal diabetes are left ventricular outflow obstructive defects and septal defects1-6, 9, 11. Cardiomyopathy also occurs but typically resolves over time.
The frequency of diabetes among women of childbearing age varies by country, age, and other factors. According to one estimate, diabetes affects approximately 2% or 1.85 million women of childbearing age in the United States. Including diabetes management as part of a preconception plan could decrease the risk for pregnancy loss and congenital malformation for approximately 113,000 births per year15. Rates of diabetes are not only high, but rising in both developed and developing countries16, 17. Of additional concern is that many women could have unrecognized or undiagnosed diabetes. One study estimates that in the United States, for every two women of childbearing age diagnosed with diabetes, there is another one with undiagnosed diabetes18.
Strategies for Prevention:
Even without considering the overall effect on women's health, these three elements -- strong evidence for causation, high relative risk for disease, and comparatively high and rising frequency in the population – combine to make diabetes a clear priority for prevention. Additionally, findings show that it is possible to reduce considerably the risk of diabetes-related malformations in pregnancy through careful monitoring and controlling of blood sugar levels before a woman becomes pregnant15, 19, 20. In practice, however, many affected pregnancies continue to occur8, 15, 21, highlighting the challenges of implementing optimal preconceptional control22.
Some findings suggest that birth defect risk may be lower among diabetic women who also took a folic acid-containing multivitamin supplement from before conception2. If confirmed, taking such a supplement could represent an additional prevention strategy for diabetes-associated birth defects. In summary, maternal diabetes is an established, serious risk for heart defects, and an achievable priority target for prevention efforts.
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20. Suhonen L, Hiilesmaa V, Teramo K. Glycaemic control during early pregnancy and fetal malformations in women with type I diabetes mellitus. Diabetologia 2000;43(1):79-82.
21. Holing EV, Beyer CS, Brown ZA, Connell FA. Why don't women with diabetes plan their pregnancies? Diabetes Care 1998;21(6):889-95.
22. Kitzmiller JL, Wallerstein R, Correa A, Kwan S. Preconception care for women with diabetes and prevention of major congenital malformations. Birth Defects Res A Clin Mol Teratol 2010;88(10):791-803.
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