How Stretch Marks Form: Why They Happen and Where

Complete Healthcare Team

Stretch marks aren’t a sign that you did anything wrong, and they aren’t really on the surface of your skin at all. They form deeper down, in the middle layer of the skin, when it stretches faster than it can keep up with. That’s why they show up during the most normal and healthy of circumstances, like pregnancy, growth spurts, and building muscle, and why creams applied to the surface can only do so much. Understanding what’s actually happening in your skin makes them far less mysterious.

Stretch marks are extremely common, they’re harmless, and they happen to most people at some point. The gynecology team at Complete Healthcare talks with patients about them often, especially during and after pregnancy, and this guide explains how they form, why they show up where they do, and what actually helps.

What Are Stretch Marks?

Stretch marks, known medically as striae, are a form of scarring in the dermis, the middle layer of your skin. When skin is stretched quickly, the collagen and elastin fibers that give it strength and flexibility get damaged and can tear. As the area heals, it forms the narrow, streaky lines we recognize as stretch marks.

The key thing to understand is that they aren’t a surface problem. They originate below the outer layer of skin, which is exactly why surface treatments have limits, and why they behave like scars rather than like dryness or discoloration you can simply wash or buff away.

How Stretch Marks Actually Form

The mechanism is essentially rapid stretch outpacing your skin’s ability to adapt. When your body changes shape faster than the skin can grow with it, the supportive fibers in the dermis break, and the healing of those tiny tears creates a stretch mark. This is why stretch marks tend to run perpendicular to the direction the skin is being stretched.

A few factors influence who gets them and how much:

• Speed of change. Rapid weight gain, growth, or muscle building is more likely to cause stretch marks than gradual change, because slow stretching gives skin time to adapt.
• Hormones. Cortisol, a stress hormone, can weaken the skin’s collagen and elastin, which is part of why stretch marks appear during hormonally active periods.
• Genetics. If your parents had stretch marks, you’re more likely to as well, since your genes influence how much collagen and elastin your skin has and how it responds to stretching.
• Age and skin qualities. Skin’s elasticity changes over time, which affects how it handles stretch.

None of these are things you did wrong. They’re mostly biology, which is worth remembering if stretch marks bother you.

The Two Stages: Red Marks to Silver Lines

Stretch marks change over time, and knowing the stages helps set expectations. Fresh stretch marks, called striae rubrae, appear as raised red, pink, or purplish lines. The color comes from blood vessels visible through the small tears in the dermis, and these newer marks may feel slightly itchy.

Over months to years, they mature into striae albae, which are flatter, silvery-white or skin-toned lines. This matters for treatment, because newer red marks tend to respond better to treatment than older white ones, which is why acting sooner, if you want to address them, generally works better.

Why Stretch Marks Show Up Where They Do

Stretch marks appear wherever skin stretches rapidly, which is why certain areas are especially common.

Pregnancy stretch marks. Known as striae gravidarum, these are among the most common, affecting a large majority of pregnant women, with estimates often cited between 50 and 90 percent. They usually appear in the second and third trimesters as the abdomen expands, and they’re driven by both the mechanical stretch of a growing belly and pregnancy hormones like cortisol and relaxin that affect the skin’s collagen. Beyond the belly, they frequently show up on the breasts and thighs during pregnancy.

Stretch marks on the breasts. The breasts commonly develop stretch marks during pregnancy, puberty, and periods of rapid size change, since the skin there stretches as breast tissue grows. This is completely normal and happens to many people.

Stretch marks on the thighs. The thighs are another very common location, and they can appear from weight gain, muscle building, growth spurts during puberty, and pregnancy. On the thighs, stretch marks often start as pink or purple streaks before fading to lighter lines.

Other common areas include the hips, buttocks, abdomen outside of pregnancy, and, in people building muscle quickly, the shoulders and upper arms.

Common Questions About Stretch Marks

Can stretch marks be prevented?

Honestly, not reliably. Because genetics and hormones play such a large role, no cream or oil is proven to prevent stretch marks entirely, despite many products marketed that way. Keeping skin moisturized and gaining weight gradually where possible may help somewhat, and staying hydrated and well-nourished supports skin health, but if you’re prone to stretch marks, you may get them regardless of what you do. That isn’t a personal failing, it’s biology, and it’s worth approaching yourself with some grace.

Do stretch marks go away on their own?

They usually fade but rarely disappear completely. Over time, red or purple stretch marks typically mature into paler, less noticeable silvery lines, and for many people they become much less visible. They generally don’t vanish entirely, though, since they’re a form of scarring. The good news is that they’re harmless and tend to become far less noticeable than they were at first.

What treatments actually work for stretch marks?

Results are modest and vary, so honesty matters here. Prescription retinoid creams like tretinoin have some evidence for improving the appearance of early, red stretch marks, though they’re not safe to use during pregnancy or breastfeeding. In-office procedures like laser therapy and microneedling can help reduce their appearance for some people, working better on newer marks. No treatment reliably erases stretch marks completely. If reducing their appearance matters to you, a provider can talk through which options fit your situation and skin.

When Stretch Marks Are Worth Mentioning to a Provider

Stretch marks are almost always harmless and don’t require medical attention. That said, a couple of situations are worth a conversation:

• Stretch marks that appear suddenly and widely without an obvious cause like pregnancy, growth, or weight change, which is uncommon but occasionally worth evaluating
• Stretch marks alongside other symptoms such as unusual weight changes, since in rare cases widespread striae can relate to hormonal conditions
• When they bother you and you’d like to understand your options for reducing their appearance

In our practice, we’re always glad to talk through stretch marks, whether the goal is reassurance or exploring treatment.

A Note on How You See Them

It’s worth saying plainly: stretch marks are a normal part of having a body that changes, and the large majority of people have them somewhere. They carry no health risk at all. Whether you want to treat them or simply understand them, both are completely valid, and neither requires you to feel any particular way about marks that nearly everyone shares.

Talk Through Your Options With Us

If you have questions about stretch marks, whether during pregnancy or any other time, or you’d like to understand what can help reduce their appearance, we’re happy to help. Complete Healthcare offers gynecology care with same-day appointments available across our 11 locations in Central Ohio, including Columbus, Pickerington, Newark, Lancaster, Marion, Marysville, and Delaware. Call us at 614-882-4343 or schedule online to get started.