I was hoping there might be a lawyer who could give some insight because I can't seem to get a straight answer.

I am a psychologist and have received a subpoena to give evidence for a client in regards family court issue. I was meant to go to court next week however the current dates have been vacated and now look to be set for mid-November. This would be fine but my previous experience has been that the next date can often also be vacated and if this happens I will be on maternity leave. I know from others experiences that they have still had to give evidence (one was even on bed rest due to pre-pre-pre-eclampsia and was required to do so over the phone). I really don't want this to happen.
Does anyone know if I have any choice in the matter? Can another psychologist offer to go instead?
Any opinions/advice/direction would be much appreciated!