How common they are

The NHS gives the figure directly: stretch marks "are common in pregnancy, affecting around 8 out of 10 pregnant women". ACOG puts the timing alongside it: "By the third trimester, many pregnant women have stretch marks on the abdomen, buttocks, breasts, or thighs."

So the honest framing is that they are the norm rather than the exception, and that not getting them is largely a matter of skin type rather than of what you did.

What they are and where they appear

The NHS describes them as "narrow, streak-like lines that can develop on the surface of the skin" that "can be pink, red, purple or brown, depending on your skin colour". They usually appear on the tummy, and sometimes the upper thighs and breasts, as the bump grows.

The mechanism is mechanical: "They happen when the middle layer of skin (dermis) becomes stretched and broken in places." The NHS makes the point that this is not a pregnancy-only phenomenon — they can happen whenever skin is stretched, including in puberty and with weight gain — though hormonal changes in pregnancy affect the skin and make them more likely.

It also names the first sign, which catches people out: "The first sign you notice might be itchiness around an area where the skin is becoming thinner."

Why some people get them and others do not

The NHS answer is short and slightly unsatisfying: "Whether or not you get stretch marks depends on your skin type, as some people's skin is more elastic." ACOG's family-history point about varicose veins applies here in spirit too — a good deal of this is inherited.

The NHS adds one modifiable factor: "You are more likely to get stretch marks if your weight gain is more than average in pregnancy."

The creams question, answered honestly

This is the reason most people arrive at this page, so here is the guidance without softening.

The NHS: "Some creams claim to remove stretch marks once they've appeared, but there is no reliable evidence that they work. There is also limited evidence about whether oils or creams help prevent stretch marks from appearing in the first place."

ACOG: "There are many products on the market that claim to prevent stretch marks. There is no proof that any of these treatments work. Using a heavy moisturiser may help keep your skin soft, but it will not help get rid of stretch marks."

Two national bodies, the same conclusion. Note what neither says: neither tells you not to use them. Moisturising helps the itch, and the itch is genuinely uncomfortable. Buying an expensive oil because it will prevent marks is buying something the evidence does not support; using a cheap moisturiser because your skin is tight and itchy is entirely reasonable.

What happens to them afterwards

The NHS: "After your baby is born, the marks may gradually fade into paler scars and become less noticeable. They probably will not go away completely."

ACOG: "Most stretch marks fade after the baby is born, but they may never disappear completely."

The colour change is the reliable part. Red, pink or purple marks lose their colour over months and settle to a paler, silvery tone that matches skin more closely. The texture change is less reliable and can persist.

Weight gain, in context

Because the NHS names above-average weight gain as a risk factor, it is worth quoting what it actually says about weight, since this is an area where advice is easily misread.

The NHS: "Most pregnant women gain between 10kg and 12.5kg (22lb to 28lb), putting on most of the weight after week 20." And, on the stretch marks page: "It's important not to try to lose weight when you're pregnant by eating less. You need to have a healthy diet during pregnancy."

It also notes that midwives or GPs may have specific advice if your BMI is over 30 or below 18.5, and that gaining too little weight carries its own risks, including premature birth and a baby with a low birth weight, which it defines as less than 2.5kg at birth.

So the sequence is: eat well, stay active, and let weight gain be what it is. Restricting food to avoid stretch marks would trade a cosmetic outcome for a clinical one.

What genuinely helps

Moisturise for the itch, not for prevention. This is the honest use case and it works for what it works for.
Keep active and eat well across the pregnancy, which is what the guidance recommends anyway.
Manage expectations about timing. Marks that appear at 32 weeks look their worst at around the time of birth and improve steadily afterwards. Judging them in the first weeks postpartum is judging them at their peak.
Wait before considering treatment. Anything aimed at the appearance of established marks is a conversation for months after birth, not during pregnancy, and the evidence for it remains thin.

Why the timing varies so much

The NHS notes that "when stretch marks appear will be different from woman to woman". Some people see the first ones at 20 weeks, some at 38, and some in the days immediately after birth as the abdomen changes shape again. There is no threshold of bump size at which they arrive, which is why comparing yourself with someone at the same gestation tells you nothing.

The itch that is not stretch marks

This is the one thing on this page that is not cosmetic. Itching in pregnancy can be caused by the skin stretching — and the NHS says so explicitly — but it can also be a sign of a liver condition called intrahepatic cholestasis of pregnancy, which needs treatment.

The pattern to act on is itching without a rash, often worst on the palms of the hands and soles of the feet, and often worse at night. That is not stretching skin, and it warrants a call to your midwife or maternity unit rather than another layer of cream.

Stretch Marks in Pregnancy