By Heather Cresswell, NP
Birthmarks are any marks on the skin that are present at birth or develop shortly after birth. Birthmarks can take many forms, shapes, and sizes and can be unexpected but are usually harmless.
The cause of birthmarks is not well understood. However, one thing is certain: they are unrelated to anything a mother did or didn't do during pregnancy.
Vascular birthmarks
Some of the most common birthmarks are vascular (a medical word for anything involving blood vessels). When blood vessels grow too fast or too big, they can be more visible than usual.
Types of vascular birthmarks include:
Nevus simplex (also called stork bites or salmon patches)
Port wine stains
Hemangiomas (discussed in more detail below)
Nevus simplex (stork bites) are usually dark pink or salmon-coloured and often occur on the forehead and eyelids. They typically fade by age 3.
Port wine stains start pink and usually turn deep purple or red. They do not fade and are not dangerous.
Hemangiomas
Hemangiomas, sometimes called strawberry birthmarks, occur when clusters of tiny blood vessels grow too quickly near the skin, forming a red and bumpy area.
Hemangiomas are more common in premature babies and babies born in multiples (such as twins). So, it's not uncommon to hear them mentioned around the NICU. They are not usually present at birth but show up within a few days or weeks. Once they appear, they grow rapidly for many months, then fade.
Most hemangiomas fade within a few years. However, if the hemangioma is close to the eyes, nose, or mouth or interferes with daily activities, a healthcare provider may recommend a medicine to speed up the shrinking process.
Pigmented birthmarks
Birthmarks not caused by blood vessels fall into the pigmented birthmark category. Pigment (colour) in our skin arises from cells called melanocytes. These cells can also cause birthmarks.
Types of pigmented birthmarks are:
Dermal melanocytosis—often called Mongolian spots—discussed in more detail below
Congenital nevi (moles or dark spots that can be raised or flat and are usually permanent)
Café  au lait spots (darkened skin with well-defined borders that do not fade)
Dermal Melanocytosis (Mongolian Spots)
Dermal melanocytosis refers to large areas that appear bluish or grey. They most often occur on the lower back or buttocks. They occur primarily in darker skin tones and people of Asian descent.
Parents may often mistake dermal melanocytosis for bruises as they deepen in colour in the days and weeks after birth. They do not cause any harm and almost always fade and disappear entirely by 3-4 years old.
Do I need to worry about my baby's birthmark?
Most birthmarks are harmless. Sometimes, your baby's healthcare provider may monitor birthmarks or recommend a referral to a dermatologist.
Some examples of birthmarks that may need to be monitored are:
Multiple hemangiomas, or ones close to the mouth, eyes, nose or joints.
More than six cafe au lait spots.
Parents and healthcare providers should monitor moles for any changes.
Adjusting to birthmarks
Birthmarks are unexpected. It is perfectly normal to feel surprised, shocked or concerned at first if your baby has a birthmark. No feelings are wrong. Talk to your baby's team about any concerns, and write down any questions you may have.
Talking openly with your child about their birthmark will help them accept it as a normal part of their body, just like their hair or eye colour.
Resources
If you are interested in seeing pictures of the different types of birthmarks, check out these websites:
Cleveland Clinic. Birthmarks
American Academy of Pediatrics. Baby Birthmarks and Rashes.
 Additional reading:
My Health Alberta. Birthmarks
HealthLink BC. Birthmarks
Heather Cresswell is a Neonatal Nurse Practitioner and health writer. As a nursing student in 1995, Heather discovered the NICU during a clinical placement and never looked back. She has spent her entire nursing career (more than 25 years and counting) caring for NICU patients (premature babies are her favourite!). When not caring for her tiny patients, Heather is also a health writer and is happy to contribute to the Canadian Premature Babies Foundation.
Heather lives with her family in Burlington, Ontario, and is a proud mom to one son.