Women who keep exercising during pregnancy give birth to babies with more advanced brains, a new study shows.
Scientists tested the brainwave activity of babies born to two groups of women, 12 days after they were born.
''Our results show that the babies born from the mothers who were physically active during their pregnancy have a more mature reaction, suggesting that their brains developed more rapidly,'' University of Montreal researcher Elise Labonte-LeMoyne said.
In the first randomised controlled trial of its type, healthy-weight women aged between 20 and 35 joined the study in the first trimester of their pregnancy and were split into two groups. One group of women exercised for a minimum of 20 minutes three times a week throughout their pregnancy. The other group did not exercise before their babies were born.
When the babies were eight to 12 days old, researchers used EEG (a brainwave test) to measure the newborns' ability to discriminate between sounds. Babies born to the women who had exercised scored higher.
Ms Labonte-LeMoyne stressed a lack of exercise did not result in babies with neurological disorders.
''We're simply saying exercise is good, don't be afraid of it, it'll make you feel better and may give a slight advantage to your child's development,'' she said.
''And if they need another little push, I tell them to consider exercising as training for the birth - it's probably going to be the most exhausting event in your life.''
Personal trainer Jen Dugard, who specialises in working with women who are pregnant, said women are increasingly concerned about staying fit during pregnancy.
She advises her clients to focus on looking after themselves rather than achieving new personal bests while exercising.
''Most mums go into motherhood in their most deconditioned state, yet they're going into the most physical job you can do.''
Tanya Kaye, 30, is due to give birth in three weeks and is still swimming, attending a Pilates class and taking part in specialised workouts.
''I just want to know I've done everything in my power to help this baby grow and develop,'' she said.