In college, you can major in any field and still attend medical school to become an OB/GYN. After medical school, you then complete a residency in OB/GYN to train and practice medicine.
Pick the major that is most interesting to you. You do not need to be a science major. Philosophy majors have the highest medical school acceptance rate in the country: https://www.usnews.com/education/blogs/medical-school-admissions-doctor/2015/08/12/shine-on-medical-school-applications-without-a-premed-major
You just need to take the medical school prerequisites (https://www.kaptest.com/study/mcat/the-prerequisites-of-medical-school/) and be involved in your community, in clinic, and in volunteering.
Learn about the medical path by reading books about pre-med preparation for medical school: https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=pre-med