Threatened To Be Fired For Having A Miscarriage While On Leave For A High Risk Pregnancy

Posted elsewhere but they suggested to ask here.

I'm in South Carolina. I work for a popular pink and orange themed donut coffee shop. I've been on leave since 6 weeks pregnant for being high risk. I found out yesterday at 9 weeks 4 days that there's no heartbeat and now I'm going to have to go through the process of like forcing my body to miscarry fully. I honestly don't know any other way to explain it.

I informed my manager of the situation this morning because it means I'll be coming back to work but just not right away because I don't really know what's going to happening next. He informed me that I have until the end of the day to say when I'm coming back or else I'm fired.

For one I can't do that because South Carolina is basically shut down from the snow we got. So I can't even call my OB to ask anything till Friday at the earliest. Only reason I know that there's no heartbeat was because I went to the ER to calm my anxiety since I'm high risk.

Is this even legal? To be fired or threatened of firing because I'm unable to provide a date for when I'll be back. It doesn't feel at all right since he knows everything is closed and he even shut down our location because of the weather.