This morning on Today, Kim revealed that she's due to give birth in July, which is actually when the Duchess of Cambridge is reportedly due, so that pretty much squares away all the tabloid covers for Summer 2013. What was really surprising tough, was that Kim explained that the real surprise about this pregnancy is that she got pregnant at all. Apparently, like her sister Khloe, Kim had fertility issues, which, up until she had to promote the new season of Kourtney and Kim Take Miami, she'd been "quiet" about. She didn't go into the details of her difficulties trying to conceive—or how she even knew she had them; wasn't she on the pill when she was with Kris Humphries? That was a plot point on Kourtney and Kim Take New York—and instead used it as a hook to get us to watch her stupid show, which supposedly will feature her troubles as a major storyline.
Kim was married for a few years when she was much younger and not famous, so perhaps she found out that way.
Also, one of her sisters has fertility problems. There may be some underlying condition that runs in the family...or Kim might just have assumed she would have fertility issues because one of her relatives did. I certainly know a couple of people who have made the same silly assumption. Most of them are parents now.