LOS ANGELES, May 12 (Xinhua) -- With pregnant women's blood sugar levels in the higher range of normal place, infants are at higher risk of birth problems, according to a new study released on Monday.

    These problems included a greater likelihood for Caesarean delivery and an abnormally large body size at birth, said the study by the National Institutes of Health (NIH).

    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, said the study.

    The study authors declined to make recommendations for acceptable blood sugar levels for pregnant women. The researchers were unable to identify a precise level where an elevation in blood sugar increased the risk for any of the outcomes observed in the study. Rather, the chances for the outcomes were observed to increase gradually, corresponding with increases in the women's blood sugar levels.

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

    The current study is the first to document that higher blood sugar levels, 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 Duane Alexander, M.D., director of the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, which provided much of the funding for the study.

    "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. It occurs in roughly 5 percent of all pregnancies in the United States.

    Mothers with diabetes during pregnancy are also at increased risk for preeclampsia, a potentially fatal disorder involving dangerously high blood pressure. Babies born to mothers 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.