Treating even mild forms of gestational diabetes appears to be beneficial, U.S. researchers say, noting that it helps cut the number of Cesarean sections and pregnancy complications.

Gestational diabetes begins during pregnancy and usually goes away after childbirth. The mother's elevated blood sugar can cause the fetus to grow too large, sometimes requiring a C-section and can bring on other problems for the mother and baby.

Treatment usually involves adjusting the diet, blood glucose monitoring and sometimes insulin shots, if needed.

While women are routinely treated for this temporary form of diabetes, some doctors have wondered whether the benefits of treating mild cases outweigh any risks.

This research, published in the New England Journal of Medicine, found that it is worthwhile to treat mild cases.

The researchers looked at 958 women at 15 medical centres, about half of whom were treated for mild gestational diabetes. Compared to those who were left untreated, women who were treated had smaller, leaner babies who were less likely to be overweight.

They were also less likely to experience "shoulder dystocia," an emergency condition in which the baby's shoulder becomes lodged inside the mother's birth canal.

Treated mothers were also less likely to undergo C-sections, or to develop preeclampsia, a life-threatening pregnancy complication that can lead to seizures and death.

There were no deaths in either group, and no difference in other birth-related complications.

"The study confirms that it is worth the time and effort to treat women with even the mildest form of glucose intolerance during pregnancy," said lead author Dr. Mark Landon of Ohio State University.

Landon noted that not only is treating pregnancy diabetes beneficial, it's simple.

He noted that 93 per cent of the women in the treatment group kept their blood sugar under control with diet alone; only seven per cent needed insulin.

Dr. John Thorp of the University of North Carolina at Chapel Hill, who also worked on the study, said the study makes clear the value to mothers and newborns of screening and treating gestational diabetes.

"Our work resolves a 40-year controversy in women's health and should be immediately helpful to both pregnant women and the clinicians caring for them," he said in a statement.

No one is quite sure why some people develop gestational diabetes, though it's thought that the hormones produced during pregnancy interfere with the body's ability to use insulin to absorb sugar from the blood.

Risk factors include being over 25, being obese and a family history of diabetes.

Last year, a Canadian study found that women who develop gestational diabetes are at greater risk of going to develop full Type 2 diabetes after their pregnancies.

According to a study published in the Canadian Medical Association Journal, 18.9 per cent of 21,000 women studied who had gestational diabetes developed Type 2 diabetes within nine years of pregnancy.