What type of degree do you need to become a maternity nurse?

There are no particular courses or majors that you need to have in order to become a neonatologist, other than the basic ones required to start medical school.

I would advise taking science and math classes, since they will help you to think analytically. And I would suggest you taking classes you like since it is your GPA and MCAT score more than anything else that will get you into medical school.