YOU HEAR: Having sex three days before ovulation boosts your chances of conceiving a girl.
AND THE TRUTH IS: A handful of small studies suggest a link between timed intercourse and gender, but the jury is still out, says Eric Surrey, M.D., medical director of the Colorado Center for Reproductive Medicine. The theory is that X-chromosome (a.k.a. girl) sperm are larger and more robust, so they can survive longer and wait for the egg to drop. "There is some logic to it, but the evidence is soft," Surrey says. Feel free to give it a shot — but don't paint the nursery pink just yet.
YOU HEAR: Eating a diet high in calcium and magnesium can increase your odds of having a girl.
AND THE TRUTH IS: In a new study by researchers at Gender Consult in the Netherlands, women who ate a diet that was low in potassium and sodium and high in calcium and magnesium and had sex three to four days before ovulation were 81 percent more likely to conceive a girl. Talk to your doctor before overhauling your diet, though: A well-balanced meal plan is crucial to the healthy development of a fetus.
YOU HEAR: Doing it "doggie-style" (sorry, there's no other way to say it) makes you more likely to conceive a boy.
AND THE TRUTH IS: It's a myth. The idea is that this deep-penetration position places sperm closer to the egg, so Y's can outswim X's, while shallow penetration positions like missionary deposit sperm farther from the egg, so slow-and-steady X sperm will outlive speedy Y sperm and get to it. But there's no evidence to support any of it. In fact, during an in vitro fertilization study, doctors put 40,000 sperm right next to the egg, and the gender odds were 50:50.