Don’t stress yourself sis. Your baby’s health will have impact. They just want to avoid paying salary for maternity period that’s why asking for resignation.
Company will be in big legal trouble if they terminate you during pregnancy period without any genuine reason.
Drop an email to HR asking details relating to maternity this way you’ll have some official documents if required at later stage On a safer side, take the print of the mail copy if in case they delete the mail from your email id without informing you.
Stay strong. Don’t resign