New York, March 11 : Pregnant women should dim the lights in their home and turn off or at least dim their screens of computer monitors and smartphones a few hours before bedtime to reduce the risk of gestational diabetes mellitus, claims a new study. Gestational diabetes is a common pregnancy complication and is known to increase obstetric complications, and the mother's risk of diabetes, heart disease and dementia. The baby also is more likely to have obesity and hypertension as they grow up. The study, published in the American Journal of Obstetrics and Gynecology Maternal Fetal Medicine, examined 741 women in their second trimester. The results showed that women who developed gestational diabetes mellitus had greater light exposure in the three hours before sleep onset. They did not differ in their light exposure during daytime or sleep or in their activity levels compared to those who did not develop it. Pre-sleep light exposure may affect glucose metabolism through sympathetic overactivity, meaning the heart rate goes up before bed when it should go down, the researchers explained. "It seems there is inappropriate activation of the fight or flight response when it is time to rest," said lead study author Dr. Minjee Kim, Assistant Professor of neurology at Northwestern University Feinberg School of Medicine. While scientists don't know which source of bright light causes the problem, it might all add up, Kim said. "Try to reduce whatever light is in your environment in those three hours before you go to bed," Kim said. "It's best not to use your computer or phone during this period. But if you have to use them, keep the screens as dim as possible," Kim said, suggesting people use the night light option and turn off the blue light. "Our study suggests that light exposure before bedtime may be an under-recognised yet easily modifiable risk factor of gestational diabetes," Kim said. /IANS