Stretch Marks During Pregnancy: When They Start

Striae gravidarum are the most common skin change of pregnancy, reported in somewhere between 43% and 90% of pregnancies depending on the population studied and how carefully anyone looked. The abdomen grows faster than the dermis can remodel, the fiber network fails along lines of tension, and the result is a scar. The timing is more predictable than most people expect.

When they start

The usual onset is the late second and early third trimester, when abdominal growth accelerates. But a review in the International Journal of Women’s Dermatology cites a study in which 43% of women developed them before 24 weeks — considerably earlier than the folklore suggests. A first-pregnancy skin check at around 20 weeks is therefore not premature, and someone who reaches the third trimester unmarked is not out of range yet either.

Who is most likely to get them

The same review reports the following contrasts between women who developed striae gravidarum and those who did not:

• Younger maternal age — 22.8 years on average against 26.6. Age is the strongest single signal in the literature; one study found severe striae in 20% of teenagers and in none of the women over 30.
• Family history — 82.8% of affected women had one, against 17.2% of unaffected women
• Higher pre-pregnancy BMI — 21.2 against 19.8 kg/m² in the same comparison
• Greater gestational weight gain, the one item on the list that is partly modifiable
• Higher birth weight — 3,078.8 g against 2,895.8 g on average
• First pregnancy, which accounts for up to 90% of cases

Read that list honestly: five of the six are things you were handed rather than things you chose.

Where they appear, and why the belly is not the only site

The abdomen dominates, following the direction of maximum tension, but breasts, hips, thighs and buttocks are common too, since those tissues also expand. Distribution differs by cause — the adolescent pattern is different again, described in stretch marks in teens, and the general mechanism in stretch marks causes.

What the trials say about creams and oils

This is where the honest answer disappoints. The Cochrane review of topical preparations for preventing stretch marks in pregnancy pooled six trials and 800 women — testing Alphastria, Trofolastin, Verum, olive oil and cocoa butter — and found no high-quality evidence that any of them prevented stretch marks, and no statistically significant difference against placebo or no treatment in either development or severity. The single product with any signal was a cream containing Centella asiatica, where one trial reported striae in 34% of the treatment group against 56% on placebo — one trial, small, not enough to build a promise on.

None of this means moisturizing is pointless. It means it is comfort for tight, itchy skin, not insurance. The full picture on prevention is in how to prevent stretch marks.

After delivery

The marks change color rather than vanish, shifting from red-purple to pale over months to years — the two phases are described in red vs white stretch marks. If treatment interests you, the window matters: the AAD notes treatment has little effect on mature stretch marks, while tretinoin at 0.05% or higher has produced up to 47% improvement and non-ablative fractional lasers 50% to 75% improvement in treated lesions. All of that belongs after the pregnancy, and after a conversation with a dermatologist.

What to raise at a prenatal visit

Mention striae if the itching is intense rather than mild, if the skin looks inflamed beyond the bands themselves, or if marks appear in places that are not stretching. Otherwise they are a cosmetic matter, and the most useful thing anyone can tell you is that gaining weight within the range your prenatal care recommends is the only lever with real evidence behind it.

This content is informational and does not replace medical consultation, diagnosis, or treatment.