If for that time you haven't done a decision about a specialty and the idea of a master's is still on you, a good recommendation from my perspective is the Family Nurse Practitioner program, since it covers all the specialties named above, you can work with adult patients as well as pediatrics and women.
If on the contrary you are decided for a specific area there is plenty of options you can search into such as Anesthesiology, Midwife, Critical care, mental, informatics, forensics, etc.
The most important is how comfortable you feel with the option chosen, which requires the prospective extensive research to find the program that matches their specific needs.
I hope that this helps you in finding the right path through your masters.
Jose Sanchez Sosa FNP-C