getting a new job at 6 months

Ok so I finally got the job I've applied to like a year ago and I'm scheduled to start at 6 months pregnant. I haven't told them yet and I'm so lost as to what to do. Would I be able to take time off for the baby? Should I tell them before starting? I'm afraid if I do that that it may affect my hiring. 
Does anyone know what rights mothers have and do you have to have served a certain time before qulifiying for like maternity leave and other related benefits?
I'd greatly appreciate your input