​Have you ever wondered why some people are born with birthmarks and others aren't? What happens when babies are in utero could have an effect on their skin. And while many birthmarks are harmless, others might be a hint of an underlying problem. There are two categories of birthmarks, vascular and pigmented.Pigmented birthmarks are usually caused by an increase in melanin in the area where they appear, according to doctors. These are known as moles, cafe au lait spots and Mongolian spots (the latter tend to vanish by adolescence). And that's almost all experts know about them! None necessarily indicate health issues, but you should always see a doctor if they grow or change colour.

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The medical world has more info on vascular birthmarks and their cause. The most common of this type are 'stork bites'. Similar to spider veins, these marks are caused by stretching capillaries, and almost half of infants are born with them. They usually fade away within 18 months of birth.Another mark commonly found on babies is infantile hemangioma. Resembling strawberries, these are benign tumours in the cells that line blood vessels. Though they usually only stick around for up to two years, about 10% grow larger over time, and can cause vision, hearing and even cognitive problems. One study from the Pediatric Dermatology Journal found that oxygen depletion in the placenta could prompt them to develop, while research from the Medical College of Wisconsin found that low birth weight is the single largest cause.

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The last major mark is known as the port wine birthmark. These appear as raised red spots on the skin, and like the others occur when capillaries do not grow correctly. While they may mean nothing, they can also signal Sturge-Weber syndrome, in which a sufferer has abnormal blood vessels throughout the skin, brain and eyes.If you have raised red spots and are experiencing other symptoms like muscle weakness or glaucoma, your birthmark could be a reason to see a doctor. And check all of your moles and spots frequently to make sure they're not changing over time: if they are, see your GP.


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