Diabetes diagnoses prior to motherhood have more than doubled in women and teenage girls in the past six years, a large California study says.

The study, conducted by hospital network Kaiser Permanente researchers, is published in the May issue of Diabetes Care.

The study examined the incidence in the onset of pre-pregnancy types 1 and 2 diabetes, as well as gestational diabetes, which develops during pregnancy.

The study participants comprised 175,249 women and teenagers from racially diverse backgrounds who delivered children in 11 Kaiser Permanente hospitals in southern California from 1999 to 2005.

Researchers discovered that between 1999 and 2005, the number of women with diabetes who delivered babies doubled to 1.82 cases per 100 in 2005 from 0.81 per 100 in 1999.

"The steps to reducing risk of type 2 diabetes must start before childbearing years: Healthy eating, active living and maintaining a healthy weight." — Jean Lawrence, research scientist

In other words, pre-existing diabetes was found in 2,784 or 1.3 per cent of all pregnant women during that period.

Researchers said 52 per cent of the participants were Hispanic, 26 per cent were white, 11 per cent were Asian/Pacific Islanders and 10 per cent were African American.

The highest incidence of diabetes was found in teenage moms aged 13 to 19 years old, a group in which the incidence increased fivefold over the course of the study.

Diabetes also doubled among women aged 20 to 39 and increased by 40 per cent among those women 40 and older.

African-American, Hispanic and Asian/Pacific Islander women were more likely to develop the condition than white women, the study found.

"More young women are entering their reproductive years with diabetes, in part due to the fact that our society has become more overweight and obese," said lead author Jean Lawrence, a research scientist at Kaiser Permanente's department of research and evaluation, in a release.

"While we currently don't know how to prevent type 1 diabetes, the steps to reducing risk of type 2 diabetes must start before childbearing years: Healthy eating, active living and maintaining a healthy weight."

Gestational diabetes occurs in 8 per cent of pregnancies, though it usually disappears following the baby's birth. It can lead to larger babies, obesity in childhood and increased risk of the mother developing Type 2 diabetes.

Gestational diabetes rate remained stable

In the study, rates of gestational diabetes remained stable, at 7.5 cases per 100 in 1999 to 7.4 cases per 100 in 2005.

Women who have diabetes prior to getting pregnant have a greater likelihood of having miscarriages, stillbirths and babies with birth defects.

"The increase in the relative proportion of pregnant women whose diabetes antedated pregnancy is a source of great concern," reads the study.

"In addition to the potential increased risk of fetal, neonatal, and childhood consequences of exposure to the intrauterine environment of a woman with long-standing glucose intolerance, the earlier onset and therefore longer duration of maternal diabetes suggests that these women may develop complications of diabetes at a younger age."

The researchers attribute the surge in diabetes to the increasing prevalence of obesity in women of childbearing age.

Women with Type 2 diabetes who are overweight and thinking of getting pregnant are advised to work with their doctors to establish well-controlled blood sugar, as well as to shed some weight.