Pregnant women with diabetes are almost four times more likely to have a baby with a birth defect, a new study has found.

Researchers at Newcastle University and the Regional Maternity Survey Office found that women with Type 1 or Type 2 diabetes had a significantly higher risk of their baby being born with a congenital anomaly than those without the condition.

The study, published in the journal Diabetologia suggests that as many as one in 13 deliveries to women with Type 1 or Type 2 diabetes involves a major birth defect.

The researchers found that blood glucose levels around the time of conception were the most important factor predicting risk.

Diabetes UK, which funded the study, urges women with diabetes who are considering becoming pregnant to make sure they understand the importance of careful planning.

The charity states on its website that it has also called for the NHS to provide better care for women with diabetes who may be planning to have a baby and that women who are thinking of becoming pregnant should attend a preconception clinic or ask their doctor to put them in touch with a diabetes specialist.

The birth defects included problems with the nervous system (such as spina bifida),

Dr Ruth Bell, the study’s lead researcher, said, "The good news is that, with expert help before and during pregnancy, most women with diabetes will have a healthy baby. The risk of problems can be reduced by taking extra care to have the best possible glucose control before becoming pregnant. Any reduction in high glucose levels is likely to improve the chances of a healthy baby.

"All young women with diabetes need to know about preparing for pregnancy, and should contact their doctor or diabetes team as soon as possible if they are thinking about pregnancy or become pregnant."

Dr Iain Frame, Director of Research for Diabetes UK, said, "The real message from this study is that the blood glucose level of the mother is important to the risk.

"This study offers clear evidence that although women with diabetes might still have a higher risk of a birth defect, they can still do something positive to reduce that risk by carefully monitoring their blood glucose level and trying to reduce it if it is high.

"We need to get the message out to women with diabetes that if they are considering becoming pregnant, then they should tell their diabetes healthcare team, who will make sure they are aware of planning and what next steps they should be taking. Blood glucose control continues to be important throughout pregnancy and should be closely monitored to ensure the best result for the baby: this is why women should be as prepared as possible beforehand."

He adds: “It also highlights the importance of using contraception if you are a woman with diabetes who is sexually active but not planning to become pregnant. This is because as well as high blood glucose levels increasing the risk of birth defects, some medications taken by people with Type 2 diabetes can cause problems in the developing foetus, and higher doses of folic acid are needed for women with diabetes to reduce the risk of complications such as spina bifida."

However, both the researchers and Diabetes UK emphasise that while the statistics are concerning, the majority of pregnancies among women with diabetes do not involve a birth defect.