Just to chime in here, I personally know two 34+ year old moms who had children in the past 2 years with Down Syndrome, after having numerous miscarriages. It seems a lot of young geeky guys commenting here forget that it's not just men who have a child so if you want to have a kid in your 30s and 40s after building a career, it's going to be difficult to find a partner at that same age who has the same goals.