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According to the Centers for Disease Control and Prevention, diabetes mellitus was estimated to affect 24 million people in the United States in 2008, an increase of 3 million over the preceding 2 years. Prevalence of diabetes, primarily type 2 disease, is expected to rise even further by 2030, as a consequence of population aging, lifestyle changes, and increasing obesity rates. Approximately 25% of adults with the condition are currently undiagnosed.
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Data suggest that this upward trend in prevalence is also affecting pregnant women. Preexisting diabetes affects 1% of all pregnancies, whereas approximately 7% of pregnant women are diagnosed with gestational diabetes mellitus (GDM), a condition traditionally defined as glucose intolerance with onset or first recognition during pregnancy. Even higher rates may be seen in certain minority groups, in particular African American and Hispanic gravidas.
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Before the introduction of insulin in 1922, women with preexisting diabetes did not often conceive. When pregnancy did occur, it commonly resulted in the death of the mother. This fact prompted Joseph de Lee to recommend in his seminal 1913 textbook that all such pregnancies be terminated. He observed that “the attempt to carry the pregnancy up to term or even to viability of the child is too perilous.”
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The introduction of insulin, as well as improvements in general obstetric care, rapidly decreased maternal mortality. However, the risk of stillbirth and neonatal death remained much higher in diabetics than in the general population until the 1960s. Since that time, there has been a dramatic decrease in perinatal mortality due to improved neonatal intensive care, fetal surveillance, and greatly improved diabetic control, the result of self-blood glucose monitoring and intensified insulin regimens. Today, if good glycemic control is achieved, the risk of perinatal mortality approaches that of the general obstetric population. Nevertheless, both preexisting diabetes and GDM continue to pose significant risks during pregnancy.
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Currently, the priorities for diabetes care providers are first to identify and control diabetes prior to conception and second to appropriately screen and treat GDM during pregnancy in an effort to prevent maternal and fetal/neonatal complications. Evidence exists that treatment of even mild GDM results in improved outcomes in both mother and baby.
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Metabolism in Normal & Diabetic Pregnancy
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To accommodate the growth of a healthy fetus, profound metabolic changes occur in all pregnant women during gestation. In particular, it is well established that insulin sensitivity decreases in normal women as gestation advances. However, despite much research, the mechanism behind this phenomenon is unknown. Alterations in maternal cortisol levels, as well as in the placental hormones including estrogen, progesterone, placental growth factor, and human placental lactogen (hPL) (also known as human chorionic somatomammotropin), have all been implicated.
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Although some degree of insulin resistance occurs in all women, only a relatively small number develop GDM. Affected women share the same risk factors as patients with type 2 diabetes, ...