Running/jogging when pregnant

[dusty]

My BF is 20 weeks and runs for pleasure about 50mins 1-2 times a week. She says her midwife isn't too concerned about it but I wondered how others have managed running while pregnant and when it started to be difficult or when it starts to be of concern (if at all) to a pregnancy.

She is 29, superfit, cycles everyday and doesn't have too large a belly yet. I can imagine she will want to be as physically active as possible for as long as she can. She has had no problems at all during her 20 weeks.

Would love to hear of your experiences/advice.