In their statistical analysis of the study results, the researchers combined several serious potential outcomes into one figure, to represent a single and primary outcome. The primary outcome consisted of all cases of newborn death, stillbirth, newborns with low blood sugar or with high insulin levels, birth-related injuries, and high bilirubin levels (an indicator of newborn jaundice). In terms of the primary outcome, there were no differences between the two groups of women. But the women who received treatment fared significantly better than the untreated women on other measures.

Specifically, compared to women who did not receive treatment, those who did were:

half as likely to have an unusually large baby, half as likely to experience shoulder dystocia during childbirth, four-fifths as likely to give birth by cesarean section, and three-fifths as likely to develop high blood pressure or preeclampsia.

"Obstetricians are concerned with the immediate risks of birth trauma which may accompany delivery of large infants to women with diabetes," Dr. Landon said.

These risks include fracture of the skull and collar bones, and injury to the nerves that connect the arm, hand and shoulder to the spine.

"Our study demonstrates that treating even mild diabetes can reduce fetal overgrowth and thus could also reduce these birth related risks."

Previous studies suggest that the higher birthweights and greater proportion of body fat seen in the newborns of women with gestational diabetes also pose increased health risks for these children later in life, Dr. Spong said. The children are more likely than other children to be overweight and, as adults, more likely to have impaired glucose tolerance, a prediabetic condition.

"The children would need to be followed long term to be certain, but it's possible that treating women with mild gestational diabetes to reduce birthweight and body fat among their newborns may benefit these children later in life," Dr. Spong said.

Source: NIH/National Institute of Child Health and Human Development