We spoke to Dr. Sophia Reid, a board-certified dermatologist, to better understand stretch marks and what to do about them.

How common are stretch marks?

Very. Studies estimate that up to 90 percent of pregnant women get stretch marks during pregnancy. The marks typically appear in the late second and early third trimester and may be accompanied by itching or mild stinging. “While there does not seem to be a difference in risk of stretch marks between ethnicities, the appearance can be different for different skin tones,” says Reid. In darker skin tones, stretch marks can appear dark brown or purple, whereas in lighter skin tones, they will appear pink or red. In almost every case, they become paler over time. They are equally common across ethnicities. 

What causes stretch marks?

Stretch marks form in the dermis, the middle layer of your skin, when the connective tissue is stretched beyond the limits of its elasticity, resulting in a tear. Once the elastin is torn, the deeper layers of skin begin to show through, and these are the lines you see on the surface of your skin. Stretch marks are in effect a scar.

Stretch marks are caused by a combination of genetic, hormonal, and mechanical factors. Genetics determine the ability of your elastin to stretch to accommodate the changes that are happening in the skin. “Generally, there is a hereditary predisposition to stretch marks,” says Reid. If your mother got them, you likely will, too. Studies have also shown that during pregnancy increased hormone levels makes skin more susceptible to scarring when stretched. And then there are the basic mechanics: Rapidly expanding skin (like that on a pregnant woman’s belly, as well as her thighs and butt) is more likely to tear. 

Can I prevent them?

There is no proven preventive treatment for stretch marks. That said, there are treatments that may affect how severe stretch marks appear. Topical treatments that increase the production of collagen and elastin fibers can help prepare the skin to stretch, and any moisturizer will help alleviate the itchiness that often accompanies the stretching. But because the disruption is happening in the middle layer of skin and not the outer layer (the epidermis), even the most diligent hydration cannot prevent stretch marks during pregnancy.

What can I do about them?

“Once you have stretch marks, there isn’t much you can do to make them completely disappear,” says Reid. However, there are treatments that will minimize their appearance. The key is to begin treating stretch marks as early as possible. Research has shown that early stretch marks (when they are still purple or red) respond better to treatments than older stretch marks (when they are already white). Now here’s the Catch-22: The most effective treatments are not cleared for pregnant or postpartum women, so be sure to check with your ob-gyn and a board-certified dermatologist before considering any new skin protocol. In the meantime, consistent moisturizing will keep the skin pliable, and Reid notes that some studies show that hyaluronic acid–based skin care can help. 

According to Reid, the most effective treatment includes

Prescription retinoid creams. These potent vitamin A derivatives are more powerful than over-the-counter retinol products and have been shown to minimize the appearance of stretch marks less than a few months old. Retinoids work by stimulating the production of collagen, making the stretch marks look more like your normal skin. 

Fractional lasers. Available only in a dermatologist’s office, these treatments use microscopic lasers to make the skin go into reparative mode to rebuild the collagen. Over multiple sessions, this can make the stretch marks look smoother and smaller in appearance. Multiple treatments—typically four to eight—are required to see visible results. Lasers can trigger hyperpigmentation in darker skin tones. 

Microneedling. This treatment involves tiny, very fine needles being passed over the skin to create micro injuries. As the skin begin to heal itself, collagen production is stimulated. Microneedling is safer than lasers for darker skin tones, but the risk of hyperpigmentation is still present. Four to eight sessions are required to see results.

How long will stretch marks last? 

Once the skin stops expanding, a stretch mark begins to heal. That process can take a couple of months or up to a year. Over time, the scar will fade and flatten out, but it will never go away completely.