Babies born to women suffering from diabetes are seven times more likely to be stillborn than those of women without the condition, research claims.
A study in Leicester of 130 pregnancies in women with type 1 diabetes between 1999 and 2006 found 3.9% resulted in stillbirth, compared with 0.55% across all births.
The results also show that 58% of births among women with diabetes resulting in the baby needing to be delivered by caesarean section, while 5.4% of babies were born with congenital malformations - both more than double the norm.
Douglas Smallwood, chief executive of Diabetes UK, said: "Diabetes UK is alarmed by these findings.
"Many of the risks these women and their babies face are avoidable if they receive the appropriate preconception care and are supported to achieve good blood glucose control during their pregnancy.
"Sadly it appears we are making little progress in tackling the problem. It is unacceptable that women and their babies are exposed to these dangers unnecessarily."
Dianne Todd, a specialist midwife at the University Hospitals of Leicester NHS Trust, added: "We have known about the health issues of pregnant women with diabetes for some time and have, over the years, made significant improvement in our provision of care and pregnancy outcomes."