runners + heart rate

dukestar5

Hi Ladies!

Does anyone know what heart rate we should aim to stay under while running or exercising during pregnancy?  I've heard 120, 140, etc.  I love running and probably log 25-30 miles a week, sometimes more if I am training for a big race.  I'm only nine weeks along, but I've kept up my usual running routine and I am participating in a half marathon next weekend.  I just want to make sure that my heart rate does not get too high.

Does anyone know the range I should stay in for exercising?  Does anyone have recommendations for heart rate monitors or how to figure out if you're in the right range?  Any other advice from running mamas? Thanks!