I think it all depends on your personality type [as a woman]. If I end up getting married in grad school, then shit, i'll be married. I want a very intimate ceremony anyways, so I don't think that planning would be a huge stressor. As a woman in science though, I feel like I will do my best work in my twenties. I don't want to be tied down with a kid while I'm supposed to be cranking out research. I am serious about my career, but I am also serious about my relationship. You don't have to choose one or the other; you just have to manage your time (and also make sacrifices occasionally). I want to have kids eventually, but that can wait until I am not working an entry level job or a post-doc.