The number of pregnant women with diabetes has more than doubled in six years, according to one of the largest health surveys of expectant mothers

Doctors fear the rise will lead to a greater risk of miscarriages, stillbirths and babies with serious birth defects

Children born to diabetic women are more likely to develop diabetes themselves

found significant jumps in pre-pregnancy diabetes in every age, racial and ethnic group

In the youngest group studied, aged 13 to 19, diabetes rose fivefold, while it doubled among women aged 20 to 39

Women aged 40 and older showed a 40% increase in diabetes over the same time period

Doctors believe the rise reflects the sharp increase in type 2 diabetes, which is driven by soaring rates of obesity

"In the US and worldwide, we're seeing an increase in type-2 diabetes. It used to be considered adult-onset diabetes, with diagnosis in the 40s, but we're seeing it in children as young as age 10