The characters of World War Z put a lot of thought and energy into fighting the zombie swarm and rebuilding society, but they put almost no thought into how they're going repopulate the planet. Sex plays a tiny role in Max Brooks's zombie-war drama, save for the occasional reference reading more like a footnote than an actual consideration of human sexuality.
Here are two examples of what we're talking about:
Another woman—I won't say what country she belonged to—tried her best to dispel the notion that sexual intercourse with a virgin could "cleanse" the "curse." I don't know how many women, or little girls, were raped as a result of this "cleansing" (7.2.16)
We were rock stars. I got more… well… if there's a bunch of little dudes between here a and Hero City that happen to look like me…[Laughs] (8.7.33)
In the first case, the sexual content, while awful, is treated in a very statistical manner and is no more sexually charged than a blurb you'd happen upon reading the nightly news. In the second case, we have a dirty joke, but—let's face it—a super tame one. And that's basically World War Z's stance on sex: tame jokes or statistical matters-of-fact. So, we're giving this one a PG rating.