According to NBC's Nancy Snyderman:
Here's how it happens--egg and sperm implant. Of course, that's your first pregnancy. But if you ovulate more than one time a month--and women do--and a sperm happens to meet that egg, and they, too, implant, guess what? You get a second fetus.
This is precisely what doctors think happened to Arkansas couple Todd and Julia Grovenburg. An ultrasound revealed that a male fetus appears … Read more