Metformin can be used to treat gestational diabetes, claim researchers in New Zealand.

Findings from a study of 751 women showed that metformin was not associated with increased perinatal complications compared with insulin.

The women were randomly assigned to insulin or metformin (with or without insulin) at 20-30 weeks gestation.

Follow-up showed that the risk of complications, including neonatal hypoglycaemia and premature birth, was similar in both groups at around 32 per cent.

Additionally, 76.6 per cent of women in the metformin group said they would choose the treatment again, compared with just 27.2 per cent given insulin.

It could signal a shift in treatment options for these women. Because metformin is not licensed for use during pregnancy in the UK, insulin or lifestyle measures are the typical modes of treatment.

NICE guidelines skirt the topic, recommending metformin use prior to conception to achieve optimal glycaemic control, but calling for documented informed consent in pregnancy.

Dr Roger Gadsby, a member of the Primary Care Diabetes Society and Warwickshire GP, said: 'The trial suggests metformin has a place. You don't have an injection or have the risk of hypos.'

Findings come as diabetes experts from across the world plan to meet to discuss if there is a need to overhaul current glycaemic diagnostic levels for gestational diabetes.

They are expected to meet this summer to discuss outcomes of the international Hyperglycaemia and Adverse Outcomes trial.

This showed that any level of hyperglycaemia is associated with pregnancy risks, even if below levels used to diagnose gestational diabetes.

The study of 23,316 pregnant women showed that for every 6.9mg/dl increase in fasting blood glucose, the odds of having a baby weighing more than the 90th percentile was 38 per cent higher.

Similarly, the odds of cord-blood serum C-peptide levels being above the 90th percentile were raised by 55 per cent.

The risk of needing a caesarean was 11 per cent higher, and of neonatal hypoglycaemia was 8 per cent. Dr Gadsby said: 'We need to take gestational diabetes seriously.'

rachel.liddle@haymarket.com

N Engl J Med 2008; 358: 1,991-2,002; 2,003-15

Blood Glucose Levels

• For every 6.9mg/dl rise in pregnancy.
• 38 per cent higher risk of large baby.
• 55 per cent raised risk of high cord-blood serum C-peptide levels.
• 11 per cent greater risk of caesarean.
• 8 per cent increased risk of neonatal hypoglycaemia.