Insurance and maternity confusing

I just found out my dad forgot to take me off his insurance when I got married then submitted his approval in october again not thinking about it so he has to keep me on it at least til next October but said he probably will til I'm 26. So my DR office has his as primary and my husband's as secondary. My husband asked his today and they said they cover everything except tests for deformities and anything abnormal. I'm not sure what they mean. This means most stuff should be covered then correct? I know because of obamacare ours both my insurance changes in January to a very shitty outcome for us so I'm not sure if much will be covered by what they are saying. But has anyone had 2 insurances and know a tad bit about how it works? I'm always confused when it comes to what insurance pays and deductibles and all that.