When to give up work in pregnancy? Self Employed Cleaner. UK?

I know this question is asked a lot on here. But I'm genuinely stuck as to when I should give up work? I'm currently 22 weeks pregnant with my first. I have my own cleaning business but am closing it down as it's not financially suitable for me to continue with it once baby arrives. I need to know in advance when I should consider giving up work as I have to give my customers notice as well as sorting out my maternity allowance. It's just as I work an active job 5 days a week I'm really unsure. Thanks :)