Personally I wouldn't tell them yet - even thought it is against the law to discriminate on the basis of pregnancy, they can and may well use another reason for not hiring you, but really it is just the pregnancy that is the issue. I'm still yet to tell my managers that I'm pregnant as I'm still on probation and they could easily turn around and tell me I'm not needed anymore, with the pregnancy being the underlying issue (of course they won't say that!) HTH and good luck xox