What causes stretch marks?
Stretch marks are very common and do not just affect pregnant women.
They can happen whenever the skin is stretched, for example when we're growing during puberty or when putting on weight. Hormonal changes in pregnancy can affect your skin and make you more likely to get stretch marks.
They happen when the middle layer of skin (dermis) becomes stretched and broken in places.
Whether or not you get stretch marks depends on your skin type, as some people's skin is more elastic.
Pregnancy weight gain
You are more likely to get stretch marks if your weight gain is more than average in pregnancy. Most women gain about 10 to 12.5kg (22 to 28lb) in pregnancy, although weight gain varies a great deal from woman to woman.
How much weight you gain may depend on your weight before you were pregnant.
It's important that you do not diet to lose weight when you're pregnant, but you should eat a healthy, balanced diet.
If you are worried about your weight, talk to your midwife or GP. They may give you advice if you weigh more than 100kg (about 15.5st) or less than 50kg (about 8st).
Preventing stretch marks
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.
Find out more about stretch marks, including possible treatments for them.
Find out more about other common health problems in pregnancy.