Beta blockers

Hi! Any other moms on beta blockers? My cardiologist scared me a little with his verbiage about it can restrict fetal growth. Apparently I have POTS and pregnancy has made me very symptomatic to where I can’t stand or walk for more than 5 minutes without passing out 😭 it’s awful and my heart rate is just all over the place so I HAVE to take the meds to try and control it. I’m 14 weeks 5 days and we have had more than our fair share of miscarriages so taking this med has me on edge. So I guess I’m asking for your experience with beta blockers and pregnancy and what if anything is your OB doing differently for monitoring the baby? Thanks in advance :)