Having kids before or After Medical school!

So I just don't know what to do. I've always wanted to have kids before I was 30. And now with medical school I don't want to wait the extra 4 years and then on top of that 4 years of residency. Being an OBGYN is my dream job but being a mother is so important to me and I want to be young when I have them. Personally i wanted to stop having kids when I was 28. I was in A early college high school program so I have my bachelors degree at 19 turning 20. Do you think I will be able to have children young. My fiancé is also in the medical field as well and is also hesitant about waiting. Do you think it's possible to accomplish medical school and residency while being a mom and a wife.