I don't necessarily have an answer to your question, but here's what happened for us: Our insurance changed 2 weeks after the girls were born. I added them to the first policy, and then everything rolled over to the new policy (different ins companies, too). The first company ended up paying everything for the birth and the NICU. The second insurance company paid nothing.
They said something about the first 30 days as well, but my girls were in the NICU for 83 days, way past the 30 day umbrella.
So, who knows, but I would expect that your insurance will cover everything for your DD, even if she's not on the policy.