For sci-fi stories, I just assumed that we had figured out a way to stop the biological clocks. So maybe you get one period when you start, and then no more until you are ready to have kids. Like in "Even the Queen" by Connie Willis (excellent story that deals with this).

For fantasy, if they live in a world with rubber, they could use a keeper (http://www.thekeeperinc.com/). It is great all the time, but especially when camping and whatnot.