Is Clarithromycin 500mg During Pregnancy Affect The Fetus?

hi. i have an acute Rhino-sinusitis for abt 2 weeks. Not better despite emthymcin taken for about 9 days. I am currently 31 weeks pregnant. Currently, my doctor prescribed Clarithromycin 500mg for 7 days (1 tab to be taken once a day). As I read on the internet that Clarithromycin is a Categoty C drug, I am now very worried if it will affect the baby? I have taken it for 4 days already.Please help!