I would also check whether your initial 22 weeks of annual leave count towards your maternity leave absence.
In my workplace we get 14 weeks mat leave which can be taken at half pay. This must be taken as the first block of leave making up the up to 52 week absence for maternity leave. We can then take annual leave or long service or unpaid leave to make up the balance of the 52 weeks, but that is the maximum absence.
And yes it does mean some women return to work for a week or two and then go back on leave (crazy).