Pregnant women should dim the lights before bedtime to reduce their risk of developing gestational diabetes, experts say.

US researchers found pregnant women who are exposed to lots of artificial light in the three hours before sleep are more likely to develop the condition.

Exposure to light at night suppresses levels of a hormone called melatonin

Lead author of the study, Dr Minjee Kim, a neurologist at Northwestern University, said: "Light exposure before bedtime may be an under-recognised yet easily modifiable risk factor of gestational diabetes."

The experts believe that exposure to light at night suppresses levels of a hormone called melatonin, disrupts the body’s internal clock, and impacts regulation of blood sugar levels.

Gestational diabetes is high blood sugar that develops during pregnancy and usually disappears after giving birth.

According to the Royal College of Obstetricians and Gynaecologists, the condition affects at least four to five in 100 women during pregnancy.

They tracked data more than 700 women to see how light exposure before bed impacted their health.

While only a small number of women developed gestational diabetes, the results revealed a trend.

Women who were exposed to bright light from their homes, TVs, computers and smartphones were five times more likely to develop the condition.