Applying for Maternity following Short/Long term disability

Has anyone here ever experienced applying for maternity leave pay (through service Canada) following a short term and long term disability (a benefit through work). Asking because I wanted to know how they would calculate the 600hrs (52wks) if I was on a medical leave for majority of the last year. Prior to that, have never claimed maternity benefits at all and have always worked as full and part time and paid the usual dues / deduction. Do they allow to go back further than 52weeks if in this scenario, I would have not been working most of last year due to the medical leave?