News

Mothers' high blood sugar increases risk for birth problems

May 07, 2008

Pregnant women with blood sugar levels in the higher range of normal — but not high enough to be considered diabetes — are more likely than women with lower blood sugar levels to give birth to babies at risk for many of the same problems seen in babies born to women with diabetes during pregnancy, according to a study funded in large part by the National Institutes of Health (NIH).

These problems included a greater likelihood for Cesarean delivery and an abnormally large body size at birth. Infants born to women with higher blood sugar levels were also at risk for shoulder dystocia, a condition occurring during birth, in which an infant’s shoulder becomes lodged inside the mother’s body, effectively halting the birth process.

It is well known that high blood sugar levels characteristic of diabetes occurring during pregnancy present risks for expectant mothers and the infants born to them.

But this study is the first to document that higher blood sugar levels, though not high enough to be considered diabetes, also convey these increased risks.

Furthermore, when the researchers mathematically adjusted for other potential causes of these risks — such as older maternal age, obesity, and high blood pressure — the increased risks due to higher blood sugar levels were still present.

‘These important new findings highlight the risks of elevated blood sugar levels during pregnancy,’ said Dr. Duane Alexander, director of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development.

‘NIH-supported studies now in progress will provide guidance on how to manage them. Until the results of those studies are available, all pregnant women should consult a health care professional about being screened for diabetes during pregnancy.’

Diabetes results from difficulty transferring sugar (glucose) from the blood to the body’s tissues. Women with diabetes during pregnancy are also at increased risk for preeclampsia, a potentially fatal disorder involving dangerously high blood pressure.

Babies born to women with diabetes — when they reach adulthood — are at higher risk for obesity as well as diabetes, high blood pressure, and heart disease.

The seven-year study involved more than 23,000 pregnant women at 15 centers in nine countries.

The results of the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study appear in the May 8 issue of the New England Journal of Medicine. The researchers were led by Dr. Boyd Metzger, professor of medicine at the Northwestern University Feinberg School of Medicine in Chicago.

Before the current study, physicians were not sure at which point elevated maternal blood sugar posed a risk for the baby, Metzger said.

Frequently, high maternal blood sugar levels accompany such conditions as obesity, high blood pressure and older maternal age — all known to increase the likelihood for Cesarean delivery.

To conduct the study, the researchers performed an oral glucose tolerance test on each woman, from the 24th through the 32nd week of pregnancy. For the test, the women fasted, after which their blood glucose level was measured. Next, the women drank a glucose solution, and then their blood glucose was measured at predetermined intervals.

Women with blood sugar levels high enough to raise safety concerns were referred for treatment and were not included in the study. The remaining women were observed throughout the study until they gave birth.

The researchers found that the higher the mother’s blood sugar levels, the greater the chances that they would deliver by Cesarean section.

In addition, the higher the mother’s blood sugar levels, the more likely the infants were to have high insulin levels and low blood sugar levels at birth.

Both conditions indicate exposure to high glucose levels in the womb. Moreover, the higher the mother’s blood sugar levels, the more likely the women were to develop preeclampsia, and the more likely their infants were to be born prematurely, and to experience shoulder dystocia.

So, for example, women with the lowest fasting blood sugar levels gave birth to abnormally large babies roughly 5 percent of the time, while women with the highest blood sugar level gave birth to large babies 26 percent of the time.

‘These relationships are continuous and generally increase incrementally over the range of blood glucose levels we saw in the study,’ he said.

Source: The National Institutes of Health (NIH)

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