Birthmarks are one of those little mysteries that many babies are born with. Some are tiny and faint, while others are more noticeable and change over time. In this episode, we explore why birthmarks happen, the different types you might see, and what they can tell you about how your baby’s skin develops. From pigmented spots to vascular marks like hemangiomas and port-wine stains, you’ll learn what causes them, why some fade and others don’t, and when it’s worth mentioning them to your pediatrician.

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Hi Vanessa,

Thank you for everything you do with the Pregnancy Podcast. I listened to your episodes throughout my entire pregnancy, and they were such a huge help. I felt so much more informed and confident going into birth because of the information you shared. My doctor was even impressed by how much I knew.

My son was born a few weeks ago, and we’re both doing great. He has a few small birthmarks, and it got me curious about what causes these. I’ve read a little online, but the explanations seem all over the place. I’d love to understand more about why birthmarks happen, and if they will go away with time. If this is something you might cover in a future episode, I think a lot of parents would appreciate it.

Thank you again for all the information you share and for helping me feel so supported during my pregnancy.

Warmly,

Hannah

Hannah, thank you for your kind words about the podcast, and I am so glad it was helpful for you during your pregnancy. Congrats on your baby boy. It is great to hear you are both doing well, and I hope you are enjoying the first weeks of motherhood.

What is a birthmark?

A birthmark is an area of skin that looks different from the surrounding skin and appears at birth or shortly afterward. These marks are very common and, although they can be concerning for new parents, they are almost always harmless.

Birthmarks form because of slight differences in how skin cells develop or function. Some are visible at birth, while others appear in the first few weeks or months of life. This happens as a baby’s skin matures and produces more pigment, revealing variations in color or texture. Melanocytes play a key role in this process. These are the cells that produce melanin, which is the pigment responsible for the color of your skin, hair, and eyes. As pigment production increases, the differences between normal and abnormal skin pigmentation become more noticeable, making some birthmarks easier to see over time.

What Causes Birthmarks?

Birthmarks occur when certain cells grow or behave differently from the surrounding skin cells during development. These differences can involve melanocytes, the pigment-producing cells that create melanin, leading to areas of darker or uneven color. They can also involve blood vessels that grow more densely in one spot, forming vascular birthmarks. In some cases, birthmarks affect other parts of the skin’s structure, such as connective tissue or lymphatic vessels, causing slight changes in texture or small, fluid-filled areas under the skin.

It is important for parents to know that they cannot cause or prevent birthmarks by doing or not doing anything during pregnancy. These differences occur naturally as a baby’s skin and blood vessels develop and are completely beyond your control. It is normal for parents to worry about how a birthmark looks or whether it will change. Let’s examine the different types of birthmarks so you have a better understanding of them.

Types of Birthmarks

There are two main categories of birthmarks: pigmented and vascular.

Pigmented Birthmarks

Pigmented birthmarks occur when pigment-producing cells (melanocytes) grow or cluster together in one area. They can range in color from tan to brown, gray, black, or even blue. The three main types of pigmented birthmarks are café-au-lait spots, moles, and Mongolian spots.

Café-au-lait Spots

“Café-au-lait” means “coffee with milk” in French, describing their light brown color. These flat patches form when there is an increased amount of melanin in the skin. They are harmless and very common in children of all skin tones.

Moles

Moles form from clusters of melanocytes that develop before birth. When present at birth, they are called congenital nevi. It is normal for moles to darken or grow as your child grows.

Mongolian Spots

The last type of pigmented birthmarks are Mongolian spots. The term “Mongolian spot” was coined in the late 1800s by a physician who observed them in babies of Mongolian descent. These types of birthmarks occur in babies of many ethnic backgrounds, and many doctors today prefer the term dermal melanocytosis. These are caused by melanocytes that get trapped or remain deeper in the skin rather than moving to the surface during development. Because the pigment is deeper, the spot appears blue, gray, or even greenish rather than brown.

Vascular Birthmarks

Vascular birthmarks occur when blood vessels form differently or cluster together in one area. These are quite common. One study estimated that they affect about 1 in 10 babies. Another found a prevalence of 20–30%. There are three main types of vascular birthmarks: salmon patches, hemangiomas, and port-wine stains.

Salmon Patches

Also called nevus simplex, salmon patches are flat, pink or red marks caused by dilated capillaries near the skin’s surface. Salmon patches on the forehead, eyelids, nose, or upper lip, are affectionately referred to as angel kisses. When they appear on the back of the neck, they are known as stork bites. These marks result from small clusters of blood vessels that developed differently during early growth in the womb. The process is random, and there is no predictable pattern or reason a birth mark appears in one area over another.

Hemangiomas

Hemangiomas are benign overgrowths of blood vessels that form in one area. Some people call these strawberry marks bec