@apphelp222 here is an important question that I don't think anyone has asked--are you planning on having one baby, or multiple? One baby is somewhat easier to plan. If your ideal family includes 2, 3, or even more kids... I really don't see how you can delay.
As others have said, whether and how to have kids is an extremely personal decision, and you can never get things down to an exact science. You or your partner could have fertility issues. You could have a miscarriage. Your family could suddenly have a crisis that means you have to put baby planning on hold. And while there are better and worse times in training to plan to have kids, you can't always plan those other variables. As my wife and I were also in our 30s when we were ready to have kids, we ultimately just decided to make the babies and figure it out later.
I will also say this--as difficult as preclinical studying may be, it does not get any easier. Clinical rotations are harder than preclinical, residency is harder than med school, and fellowship/junior attendinghood is harder than residency. And the baby doesn't become "easy" after 6-12 months either. For all of these reasons, whenever I give advice on these kinds of questions, I almost always advise people that if they and their partner are ready to just go for it. But ultimately it's a question that only you and your partner can make.
As to your specific questions regarding rotations, that is going to be school-dependent on the kinds of accommodations that are possible. There may or may not be something in your school handbook which addresses this, and what is in the handbook may or may not reflect what actually happens IRL. I suspect you don't really want to talk about family planning with your dean, but if there are upper level students who had kids during school they might be a good person to talk to in order to get a sense of how your school handles cases where students have a kid during school.
Good luck.
