I was out on medical leave specifically maternity leave. I am relief. Terminated by employer. Can they do this? I was trying to return and told them.

I had my baby a month early. Kept management informed through everything even the birth and her NICU stay. Contacted me in june asking of my return. I said I was trying to secure respite care for her as she has a feeding tube. Manager told me they were contacting HR and then not even a month later I get a letter from my manager stating I had been terminated. I had worked for the company 12 years.