I don't think either has any bearing, no matter what your age. It just depends on a lot of factors at the time of attempted conception (egg and sperm quality, hormonal balance, clear tubes etc.) You often hear of people having difficulty conceiving--whether in their 20s or 40s--but then once they have one child they get pg again practically just by looking at their man. You often hear of the opposite too, hence the term "secondary infertility" (there wouldn't be a name for it if it didn't affect a lot of people). Sorry, I'm probably not helping much, but from what I've read and heard over the years I really don't think whether you've been pregnant or not can increase or decrease the likelihood of conceiving in the future.