Striae distensae. It's an ominous-sounding term for a deeply unwelcome skin condition: stretch marks. Technically tears in the dermis caused by a breakdown in collagen and elastin (the skin's structural proteins), stretch marks can accompany any major weight fluctuation, particularly if the change is rapid. While they can afflict everyone from bodybuilders and yo-yo dieters to teenagers on growth spurts, they most notoriously take up residence on the blossoming bellies of moms-to-be.

Though no hard stats exist, New York City–based dermatologist Amy Wechsler estimates that up to 70 percent of pregnant women get stretch marks to some degree. Beyond that, the crystal ball clouds over; according to Wechsler, not only do genetics play no definitive role in determining which pregnant women succumb, but it's perfectly normal to have no stretch marks with one gestation and loads with another. "They seem to run in families," she says, "but they're tied more to the amount and speed of weight gain. You can't predict who'll get stretch marks."

While most stretch marks fade with time, generally leaving a faint pattern of stringy scar lines, it would of course be preferable to make them disappear entirely—or to skip them in the first place. Yet "women are bizarrely apathetic about stretch marks," says Tanya Kazeminy Mackay, marketing director for Mama Mio, a luxe London-based maternity skin-care line. "You can see they put a lot of money and effort into having perfect skin. But when I ask them what they did to prevent stretch marks, they say, 'Nothing. You either get them or you don't.'"

Suffice it to say that Mackay, whose company produces a stretch-mark remedy, doesn't see it that way. "It's really about putting up a fight," she says. "And you don't have to do anything major—just rub your belly with a nourishing, lovely-smelling oil."

These lotions and potions may help prevent or reduce the appearance of stretch marks, either by using ingredients like botanical extracts and vitamin C to boost the synthesis of collagen or by infusing the skin with moisture. Enhanced collagen production can help thicken skin that has been or is about to be stretched to the point of tearing. And hydrating products keep skin looking plump and taut, which diminishes the appearance of flaws, according to New York City dermatologist Dennis Gross.

Wechsler doesn't see any harm in the umpteen belly butters currently crowding store shelves, but she does have one caveat. "Some women are allergic to certain fragrances or ingredients," she says. "So it's best to do a spot test for a couple of days first."

Once you're in the clear on that front, it's time to roll up your sleeves. These creams only work if you use them consistently—usually twice a day for at least three weeks before you'll see a difference. Of course, given that the process involves a mini massage, being assiduous shouldn't be a problem.