Does anyone know about maternity leave?

Hi guys. Is maternity leave only for full time employees? I just thkught it was weird at work today. When I got there my head supervisor asked me my due date because corporate wanted to know. Then 30 mins before my shift is over, they came and told me my hours got cut by 30 mins. Where I'm from 30 hours a week is full time and that is what I had, now I'm not considered full time anymore because of my 30 min a day loss. Can you help me understand how maternity leave works