Now, doctors at Houston's Baylor College of Medicine are conducting a "sex selection" study that will allow couples to make that wish come true --- letting them actually pick their baby's gender.

"We want to know whether using this technology for elective non-medical reasons is a good idea," said Dr. Sandra Carson, director of Baylor's Assisted Reproductive Technology program.

Doctors often analyze embryos for genetic defects, some of which are more common in boys or girls. But in the Baylor study, up to 200 couples going through in vitro fertilization will be allowed to pick either male or female embryos, so researchers can better understand their motivation.

"Before we make the procedure available in a routine, clinical way, I think it's a good idea to get actual facts from couples who are actually doing it," said Carson.

Couples must answer detailed questions about why they want a boy or a girl and how their expectations may differ between having a son or daughter.