NZ riding 'tsunami of diabetes'

The "tsunami" of diabetes is being reinforced by a sharp rise in the number of women who have the disease when pregnant, increasing their babies' risk of developing it.

At National Women's Hospital in Auckland, the number in the diabetes-in-pregnancy clinic more than doubled, to 460, in three years when the total number of births remained static.

Waikato Clinical School specialist Professor David Simmons presented the figures to the Medical Sciences Congress in Queenstown yesterday. He said they illustrated the "tsunami of diabetes in this country".

"This epidemic is moving extremely fast. What's scary now is what's happening to those babies."

It is estimated that 120,000 people have been diagnosed with type 2 diabetes, and as many again are undiagnosed. The number diagnosed is expected to exceed 165,000 by 2021.

A survey in the 1990s found that 3.1 per cent of Pakeha and 8.3 per cent of Maori had been diagnosed with the disease.

Treating diabetes and its complications costs $340 million annually, estimated to rise to $1 billion in 2021.

The increase in diabetes in pregnancy is linked to the rise in the wider population, leading to more women of child-bearing age developing the disease. It is also linked to delayed child-bearing, because the diabetes rate rises with age.

Babies born to mothers with diabetes are at risk of a range of health problems, from stillbirth or getting stuck during birth because they are too big, to cognitive impairment, kidney damage, obesity and diabetes.

In one overseas study, children of mothers who had diabetes in pregnancy had about a three times higher risk of developing the disease than older siblings born before their mothers developed the disease.

This shows diabetes in pregnancy is a stronger force in passing on a predisposition to the disease than simply inheriting genes for it from either parent. Dr Janet Rowan, a diabetes specialist at National Women's, calls this the "inter-generational amplification of diabetes".

The number of women at the diabetes-in-pregnancy clinic with type 1, an auto-immune disease that usually starts in childhood or adolescence, is stable at 25 to 30 a year.

The number with diagnosed type 2 diabetes, which is associated with obesity, diet and lack of exercise, has risen to about 60, from 30 a year.

The rest have gestational diabetes - a high level of glucose in the blood first noticed during pregnancy. It occurs because the body cannot produce enough insulin in response to changes that occur in all women while pregnant.

Of the 70 per cent of the clinic's gestational diabetes patients who return for blood-glucose tests six weeks after birth, 10 per cent have type 2, 15-20 per cent have impaired glucose tolerance (a pre-diabetic condition) and in the rest, glucose levels return to normal.

Diabetes in pregnancy is treated with insulin injections, but traditionally not with the oral diabetes medicine metformin because, unlike insulin, it crosses the placenta.

But Dr Rowan said National Women's was involved in a trial of giving pregnant women metformin because its use overseas indicated it was safe.