Stretch marks are scar-like streaky areas that appear in overstretched skin. Underlying tissue expansion is the most common cause, so they develop most often during the growth spurt in adolescence and on the expanding abdomen in the third trimester of pregnancy.

They can also occur in body builders, as a consequence of rapid weight gain, and in some medical conditions where the skin is exposed to excess amounts of a hormone called cortisol. Early stretch marks are usually red or purple. Over time, stretch marks lose their colour and become white or silvery in appearance.

The visible layer of skin (epidermis) is made from several sheets of cells and functions as a barrier for the underlying tissue. Epidermal cells born in the bottom sheet push up through the layers to replace old, dead skin cells that are constantly being shed. The epidermis also contains melanin – the pigment responsible for skin colour.

Beneath the epidermis is the dermis. This deeper layer contains sweat glands, sebaceous glands, hair follicles, blood vessels and nerves. The dermis is made from two types of fibre, being collagen, which gives the skin its strength, and elastin, which provides skin with its elasticity.

A stretch mark is formed when:

• The skin is stretched as a consequence of underlying tissue expansion.
• There is an inflammatory reaction in the skin that is responsible for the characteristic red or purple colour.
• The inflammation eventually fades and is replaced by scar tissue. This produces a thinned epidermis, loss of dermal elastin, and a replacement of the dermis by abnormally dense collagen fibres.
• The scarring is characteristically white or silvery in appearance and permanent.

Stretch marks are red, pink, or brown streaks on the skin. Most often they appear on the thighs, buttocks, abdomen, and breasts. These scars are caused by the stretching of the skin, and usually appear in the second half of pregnancy.

Some women notice other skin changes during pregnancy. For many women, the nipples become darker and browner during pregnancy. Many pregnant women also develop a dark line (called the linea nigra) on the skin that runs from the belly button down to the pubic hairline. Patches of darker skin usually over the cheeks, forehead, nose, or upper lip also are common. Patches often match on both sides of the face. These spots are called melasma or chloasma and are more common in darker-skinned women.

What might help:

• Be patient — stretch marks and other changes usually fade after delivery.

Evidence suggests that the application of creams and lotions can't prevent stretch marks. However, not all preventative treatments have been evaluated, and some treatments have shown promise in individual studies.

Stretch marks naturally fade and usually become less conspicuous over time, so in many cases, treatment may not be necessary. Various treatments have been used in the management of red, purple or white stretch marks. While some creams may improve the appearance of early stretch marks, lasers and IPL therapy may also be beneficial.