Arkansas couple Todd and Julia Grovenburg found out that they were having a baby and then discovered they were having two bundles of joy but the babies aren't twins. An ultrasound revealed that a male fetus was conceived a full two-and-a-half weeks after the woman became pregnant with a baby girl, according to reports from local media. The Grovenburgs' obstetrician confirmed the case to Arkansas television station KFSM-TV. The pregnancy is believed to be a case of a rare condition known as superfetation, or conceiving while pregnant. The pregnancy may sound weird, but it is possible, according to NBC's Dr. 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," Snyderman said during MSNBC's Dr. Nancy Thursday. "You just have to hope it happens within that early window." Due dates for the babies are the end of 2009 and early 2010, reports say.