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Mother's Size during Pregnancy, Baby's Birthweight, and the Insulin Resistance Syndrome
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What is the problem and what is known about it so far?
Insulin regulates the body's sugar, protein, and fat metabolism. In the insulin resistance syndrome, the body's tissues lose their sensitivity to insulin. To overcome this resistance, the body puts out more insulin, leading to high levels of insulin in the bloodstream. When the available insulin fails to overcome the tissue resistance, high blood sugars develop (diabetes), often accompanied by high blood pressure and high blood levels of triglycerides (a type of fat). The risk of developing this syndrome is greater in people who become overweight as adults. Recently, it has been suggested that being small at birth also increases the risk of developing the syndrome later in life. This increase in risk could be explained if the changes that occur in a developing baby's body in response to lack of nourishment during pregnancy become permanent. The insulin resistance syndrome has become more common in developing countries in recent years.
Why did the researchers do this particular study?
The researchers wanted to test the idea that the insulin resistance syndrome may be more common in developing countries now because many people who were exposed to poor nutrition as fetuses when the countries were poor are now becoming fatter as adults as the countries become prosperous.
Who was studied?
627 men and women born in Beijing, China, in about 1954.
How was the study done?
The researchers measured study subjects' height; weight; blood pressure; and levels of blood sugar, triglyceride, and insulin. They also collected information on the study subjects' birthweight and the height and weight of the study subjects' mothers during pregnancy to estimate whether they had been undernourished.
What did the researchers find?
After accounting for sex and adult body size, low birthweight was associated with high blood pressure and high levels of blood sugar, insulin, and triglycerides. Low maternal body size (suggesting poor nutrition during pregnancy) was associated with raised blood sugar, insulin, and triglycerides but not with high blood pressure.
What were the limitations of the study?
Although the study is consistent with the idea that maternal undernutrition is a cause of the insulin resistance syndrome, it does not conclusively prove the connection. Thus, we do not know for sure that improving nutrition during pregnancy would prevent the insulin resistance syndrome.
What are the implications of the study?
This study suggests that fetal undernutrition accounts for part of the risk of the insulin resistance syndrome. The effect of fetal undernutrition seems to be separate from the risk associated with adult obesity. It is possible that improving the nutrition of pregnant women may reduce the occurrence of the insulin resistance syndrome in their offspring.
Article and Author Information
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The summary below is from the full report titled “Effects of Infant Birthweight and Maternal Body Mass Index in Pregnancy on Components of the Insulin Resistance Syndrome in China.” It is in the 15 February 2000 issue of Annals of Internal Medicine (volume 132, pages 253-260). The authors are J. Mi, C. Law, K.-L. Zhang, C. Osmond, C. Stein, and D. Barker.
- Copyright ©2004 by the American College of Physicians
