Experts have warned of a 'concerning' rise in the number of UK women suffering a dangerous pregnancy complication that can result in stillbirth.Cases of gestational diabetes have risen by 60 per cent in five years, new figures show. In 2018, one in 12 expectant mothers in England would develop the condition. By 2022, this figure had risen to one in eight.Gestational diabetes happens when blood sugars become very high in pregnancy but return to normal after the baby is born.This happens because the body struggles to keep up with the foetus' increased requirement for insulin – which converts the sugars in food into energy.The condition affects the functioning of the placenta, which delivers food and oxygen to the baby, increasing the risk of a host of problems including high birth weight, trouble breathing and, in rare cases, stillbirth.It can also drive blood pressure up to dangerously high levels in the mother, risking stroke and heart attacks.Experts have linked the surge in cases to the increasing age and waistlines of UK expectant mothers. Diagnoses of gestational diabetes have risen by 60 per cent in five years Obesity is the biggest risk factor for the condition, accounting for roughly half of all cases. This is due to the impact of extra weight on the body's production of insulin. Sensitivity to the hormone also naturally decreases with age. Data published by the Office for National Statistics shows that maternal age has risen steadily over recent decades as more women have children later in life. The findings come as a recent study highlighted a 70 per cent surge in type 2 diabetes among 20-something women in England over the last decade. The researchers, from Imperial College London, blamed expanding waistlines for the rise – with the body mass index (BMI) of young women increasing more than any other group since 2011.The average BMI of female diabetics under 30 grew from 37.7 to a morbidly obese score of 40.7.Roughly one in five pregnant women in the UK are now classified as obese, data shows.Around half of women diagnosed with gestational diabetes will develop type 2 within five years.The latest research, published in the journal BMJ Medicine, analysed NHS maternity data covering more than 2.3 million mothers and around 2.8million births across 184 hospitals in England between 2018 and 2022. The study authors, led by researchers from the University of Edinburgh, found a diagnosis of gestational diabetes was associated with an increase in the odds of a premature birth, when a baby is born alive before 37 weeks of pregnancy.