Hmmm ~ and what about YOUR financial needs for your family?
Why are you being 'expected' to forgo income while they are maternity leave ~ increasing their family was not YOUR choice?
To be honest clients do not get to CHOOSE to drop down from a full time space to a part time space automatically here ... if they notify me of their 'desire' to do that than I tell them if it is an option or not based on availability of the space in my program ~ and my own financial needs for my business! They must give me at least two weeks notice of 'desire to terminate' the contract in order to apply their security deposit otherwise they forgo it in lieu of the notice.
My business plan currently only allots for ONE part time space so if it is currently full the clients option would be to pay for their current full time contract to ensure that the space is there for them or withdrawal from their space and go onto the witting list to return when their mat leave is over or seek alternate arrangements ~ which ever risk is better for them.