What Causes Frequent PVC's And Being Asymptomatic During 22nd Week Of Pregnancy?

I am 22 wks gestation, first baby. I have been experiencing frequent PVC's for two days even while at rest however am asymptomatic at this point. At what point should I be concerned/notifiy my OB? I'd like to avoid the whold gammet of seeing a cardiologist and going through several tests just to see it's normal. I'm a Neurovascular/Surgical ICU nurse, so my red flags are different than the lay person. Thanks!
K