Massive hours cut since I announced pregnancy

[StillPukin]

I'd love some advice; I'm guessing my hands are tied but hoping somebody would know better..

I work in a respite unit with adults with learning/physical disabilities. I am employed on a casual basis so the number of shifts vary but I usually work between 4 - 7 shifts per week. Since I announced I was pregnant my hours have been cut to a maximum of 1 shift per week and I've just had 3 weeks with no work at all.
The only 'problem' I have is that company policy will not allow me to push a wheelchair. I am fit and healthy otherwise. We have a maximum of 4 service-users in at a time with a maximum of 2 wheelchair users (it is unusual to have 2 wheelchair users at one time as space is a bit limited).
I just cant afford to lose so much work but I'm thinking with me being employed on a casual basis there is nothing I can do.

Does a casual basis mean you are bank work or relief? Have you signed a contract of any kind?

Yes its like bank staff.

Yes I have signed a contract but nothing about the hours.

How long have you been working 4-7 shifts per week?

Are you on a zero hours contract then? Regardless of status all employers have a duty to carry out a risk assessment on pregnant ladies, only then can they determine (with you) what tasks are suitable etc. this should then be carried out on a regular basis until you go on maternity leave.

I have been working these shifts since March - so about 4 months.

Yes its a zero hours contract. And, yes they did carry out a risk assessment and decided I was ok for everything apart from pushing wheelchairs.

(Thanks for your replies)