Pregnancy - Pre-existing condition?

My gf works for a very small employer which does not offer insurance. She just had an unplanned child (mine). I have been insured for over 2 years with no gaps in enrollment. If I marry her and switch to a family plan, will this pregnancy be covered? Are there loopholes for bcbs to now cover this? If so, what are the loopholes specifically? She has just applied to medicaid. So I think it might be better to not marry her until after the child is born. Will medicaid not cover her if they find out who the father is, and he has insurance? I am very frightened here. Please help.