Many schools offer an FNP program as opposed to other programs like acute care and psych. You will do several different clinical rotations in this program including pediatrics, women's health, and primary...I'm missing one but can't think of what right now. FNP does give you a broad scope of practice. Once you have that degree, you may be able to find other certifications that help you specialize in your general area of interest.
For example, I am a psych NP and have worked in substance abuse and enjoy it. There is a CARN-AP certification specifically for this field. If I were you would, I would to see what is available in the way of other certifications that you could add to the FNP degree. There are a few programs available that specialize in womens health nurse practitioner. This would pigeon hole you though.