Women who exercise during pregnancy reduce their risk of developing gestational diabetes, a new study has shown.

Gestational diabetes is a type of diabetes that develops during pregnancy - most often in the second or third trimester. It usually disappears after the baby is born, although women who develop it are at an increased risk of developing type 2 diabetes later on.

It also increases the risk of a number of potentially dangerous conditions during pregnancy, including pre-eclampsia and high blood pressure. Furthermore, the children of mothers who had gestational diabetes have an increased risk of developing diabetes themselves and are also more likely to become obese.

Spanish researchers set out to assess the impact of exercise during pregnancy on gestational diabetes. They looked at 13 trials involving over 2,800 women.

They found that women who usually did little or no exercise, but were then enrolled in an exercise programme during pregnancy, reduced their risk of developing gestational diabetes by over 30%.

Women who exercised throughout their pregnancy reduced their risk by 36%.

The results were strongest among those who combined aerobic exercise, toning , strength and flexibility.

The researchers also noted that exercise during pregnancy reduced excessive weight gain during this period. Those who exercised were an average of one kilogram (2.2lbs) lighter than those who did not, and these results stood even if the woman only began exercising during the second trimester of pregnancy.

"Exercise is not something to be feared during pregnancy - the moderate levels of exercise used in these studies had significantly positive effects on health and were found to be safe for both mother and baby," the researchers said.

Details of these findings are published in the journal, BJOG: an International Journal of Obstetrics and Gynaecology.

For more information on pregnancy, see our Pregnancy Clinic here