Women who develop diabetes during their pregnancy are at higher risk of developing Type 2 diabetes in the nine years after they give birth, suggests new research.

Researchers at the University of Toronto, Mount Sinai Hospital and the Institute for Clinical and Evaluative Sciences studied 659,164 Ontario women who had no pre-existing diabetes.

Of these, 21,823 developed gestational diabetes. They tracked them for nine years and found that these women were 20 per cent more likely to develop Type 2 diabetes in that time period than those who did not have the pregnancy condition.

The study also found that gestational diabetes is linked to older mothers, those women who live in low-income neighbourhoods and in urban areas.

"These women may benefit from both preventative interventions and regular screening," say the researchers who add that physicians and policy makers should advise and screen these women in light of these findings.

The study did not factor in the effects of ethnicity, obesity and level of fasting glucose in pregnancy on the development of Type 2 diabetes.

While the reason for the elevated risk is unknown, the researchers note that "during pregnancy, women with gestational diabetes display metabolic abnormalities similar to those of people with type 2 diabetes mellitus, such as insulin resistance."

The study was conducted from April 1, 1995, to March 31, 2002. It is published in the July 29 issue of the Canadian Medical Association Journal.