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Gestational diabetes linked to cardiovascular disease later in life

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A new study has found that women who develop gestational diabetes during their pregnancy are at increased for atherosclerosis (hardening of the arteries). The findings were published on March 12 in the Journal of the American Heart Association.

Gestational diabetes is a type of diabetes that appears during pregnancy and usually disappears after the pregnancy. The study authors note that a history of gestational diabetes increases lifetime risk of type 2 diabetes and the metabolic syndrome, which increases risk of cardiovascular disease. However, they note that it is unclear whether gestational diabetes increases risk of early atherosclerosis independent of pre‐pregnancy obesity and subsequent metabolic disease. Therefore, they conducted a study to address that issue.

The study group comprised 2,787 women (age: 18 to 30 years) who were enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The investigators evaluated 898 women (47% black) who did not have diabetes or heart disease at baseline (1985‐1986). The women delivered one or more children post‐baseline births,. The women had a history of gestational diabetes during those pregnancies and had common carotid artery thickness measured in 2005‐2006. The investigators conducted a statistical analysis to evaluate the associations between gestational diabetes and common carotid artery thickness; the data was adjusted for race, age, parity, and pre‐pregnancy cardiometabolic risk factors. The researchers also evaluated mediating factors (weight gain, insulin resistance, blood pressure), and diabetes or metabolic syndrome during the 20‐year period. Among the 898 women, 119 (13%) had gestational diabetes (7.6 per 100 deliveries). The average age of the women was 31 years at the time of last birth and 44 years at common carotid artery thickness measurement for both the gestational diabetes and non‐gestational diabetes groups. The average common carotid artery thickness was 0.023 mm higher for the women with gestational diabetes than those without. However, the difference was less in women who were overweight before pregnancy.

The authors concluded that a history of gestational diabetes may be a marker for early atherosclerosis independent of pre‐pregnancy obesity among women who have not developed type 2 diabetes or the metabolic syndrome.

The study authors are affiliated with Kaiser Permanente Northern California (Oakland, CA), University of California (San Francisco, CA.), University of Minnesota (Minneapolis, MN), University of Oslo (Oslo, Norway), and University of Alabama at Birmingham (Birmingham, AL).

Gestational diabetes is a condition in which a hormone made by the placenta prevents the body from using insulin effectively. Glucose builds up in the blood instead of being absorbed by the cells. Unlike type 1 diabetes, gestational diabetes is not caused by a lack of insulin, but by other hormones produced during pregnancy that can make insulin less effective, a condition referred to as insulin resistance. Approximately 3-8% of all pregnant women in the US are diagnosed with gestational diabetes.

Although the cause of gestational diabetes is not known, there are some theories as to why the condition occurs. The placenta supplies a growing fetus with nutrients and water, and also produces a variety of hormones to maintain the pregnancy. Some of these hormones (estrogen, cortisol, and human placental lactogen) can have a blocking effect on insulin. This is called contra-insulin effect, which usually begins about 20 to 24 weeks into the pregnancy. As the placenta grows, more of these hormones are produced, and the risk of insulin resistance becomes greater. Normally, the pancreas is able to make additional insulin to overcome insulin resistance, but when the production of insulin is not enough to overcome the effect of the placental hormones, gestational diabetes results.

Although any woman can develop gestational diabetes during pregnancy, some of the factors that may increase the risk include the following:

  • Overweight or obesity
  • Family history of diabetes
  • Having given birth previously to an infant weighing greater than 9 pounds
  • Age (women who are older than 25 are at a greater risk for developing gestational diabetes than younger women)
  • Race (women who are African-American, American Indian, Asian American, Hispanic or Latino, or Pacific Islander have a higher risk)
  • Prediabetes, also known as impaired glucose tolerance
  • Although increased glucose in the urine is often included in the list of risk factors, it is not believed to be a reliable indicator for gestational diabetes
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