Stretch marks develop when the collagen in the skin is stretched beyond its elastic limit," Dr Justine Hextall, consultant dermatologist, at The Harley Medical Group told HuffPost UK Parents.
"This causes fissuring which appears as stretch marks in our skin."
During the latter stages of pregnancy specifically when the baby is rapidly growing, a woman's skin cells rupture due to being pulled apart so much.
When the cells rupture they will also leave scarring - the stretch mark.
"Some women have a genetic disposition to stretch marks, so if your mum had them you might be more likely to have them."
Dr Hextall agreed, adding: "There are some women who may just have more elastic skin and can sail through growth spurts and pregnancies with perfect skin, others are not so lucky.
"It is that old-age, look at your mother!"
How can I prevent getting stretch marks?
Before noticing stretch marks have developed, there are a number of things women can do to prevent them.
No single thing will always work, so understanding how you can look after your skin as early as possible will be an advantage.
Dr. Erich Schulte, founder of QMS Medicosmetics said an effective method to prevent stretch marks is a combination of regular exercise and healthy nutrition.
Maintaining a healthy weight will minimise any rapid weight gain that could contribute towards excessive stretching of the skin.
He told HuffPost UK Parents: "Boost your routine with supplements ideally containing Vitamins E and C (like Intravital Plus) and make sure you choose skincare products that will strengthen the collagen and elastin fibres in your skin tissue before you're further along in your pregnancy."
Dr. Kishan Raichuram, skin health expert at IGDP, said another way to prevent stretch marks is through keeping your skin as healthy and hydrated as possible.
"While it's impossible to entirely prevent them, pregnant women can improve skin condition to hopefully reduce the chances by keep the area well moisturised and nourished," he said.
Dr. Schulte agreed, adding that preparing your skin as soon as you know you are pregnant will help strengthen it.
He explained: "This will make your less prone to damage and injury to the tissue. It will also help restore the skin post-pregnancy.