How Does Baby Hair Texture Work?

To understand your baby’s changing hair, let’s start with some key hair terms:

• Hair Shaft – You’re probably already familiar with the hair shaft—right now, you might have thousands of them tied up in a ponytail or clipped to the side with a bobby pin. The hair shaft is the part of your hair that isn’t anchored below the surface layers of skin in the hair follicle.
• Hair Follicle – A hair follicle is a bit like a tunnel in the epidermis—the surface layers of the skin—and goes all the way down into the dermis—the thicker layer of the skin that resides below the epidermis. This is where hair is “grown.”
• Hair Root – The hair root, or the bulbous base of the hair shaft, anchors your hair to the follicle.

For every individual hair strand, the hair growth cycle occurs in three stages:

• Anagen Phase – In the anagen phase, cells quickly divide at the hair’s root at the base of the follicle. This cell growth pushes the hair out of the follicle and out over your baby’s scalp. This phase lasts between two and seven years.
• Catagen Phase – The catagen phase marks the end of the hair’s active growth. For two or three weeks, the hair is cut off from the protein-supplying capillaries in the base of the follicle, preventing the strand from growing.
• Telogen Phase – During the final stage of the hair growth cycle, the hair follicle rests. For two to four months, no new hair growth occurs, and instead, you may shed some of your hair. In fact, about 25 to 100 telogen hairs are shed normally each day. At the end of the telogen phase, the cycle begins right back at the anagen phase. Thankfully, these phases apply to individual hair strands, and not every follicle is on the same schedule. Otherwise, every two to seven years we’d all be bald!

Pregnancy Fun Fact: During pregnancy, the increase in hormones tends to prevent this final telogen phase, resulting in thicker hair. When the hormone levels return to normal (typically around 3-4 months post-delivery), this can result in excessive hair loss. This phenomenon is called telogen effluvium.

This three-part cycle doesn’t begin at birth. In fact, this cycle of hair growth only applies to terminal hair, which is the hair we have as adults. Terminal hair typically grows in by the age of two, and two stages of hair development occur before the terminal stage.

When Does Baby Hair Texture Change: The Phases of Baby Hair

During his first 24 months, your baby’s hair texture will dramatically change as it goes through three phases:

Baby Hair Phase 1: Lanugo

While in utero, your baby’s hair follicles produce a soft, thick hair called lanugo. This unpigmented hair begins to appear at five months of gestation and grows all over your child’s body as well as her head. Scientists are still developing theories as to the biological function behind lanugo, but a 2009 study suggests that this hair might play a role in fetal hormone development.

Usually lanugo hair is lost during the later stages of gestation and absorbed into the amniotic fluid. However, sometimes your child will be born with her lanugo—this is perfectly natural. Typically, at birth, your child’s lanugo hair is in the telogen phase, meaning it’s primed for shedding within the next few weeks.

Baby Hair Phase 2: Vellus Hair

Lanugo hair is replaced with the finer, nearly transparent body hair known as vellus hair. If you want an immediate visual for these hairs, just take a look at the fine hairs on your arm, the back of your hands, and even your torso. These vellus hairs can be found all over your baby’s body, even on the top of your baby’s head. According to Advanced Neonatal Care, vellus hairs can make up between 6-25% of your baby’s scalp hair. The rest will either be lanugo or terminal hair, depending on the stage of your baby’s hair growth.

Baby Hair Phase 3: Terminal Hair

Throughout these phases, your baby’s hair follicles are growing and developing into his unique shape and form. By about two years of age, your child’s vellus scalp hair will be replaced with thicker, longer, and darker hair. These hairs are your child’s terminal hairs—adult hair. These hairs will then cycle through the anagen-catagen-telogen phases mentioned above.

Puberty Fun Fact: As your child progresses through puberty, vellus hair will develop on the face, armpits, chest, abdomen, legs, arms, pubic area, and feet. This is colloquially called “peach fuzz.” For boys (much more so than for girls), this vellus hair will transition to terminal hair.

How Does Baby Hair Texture Change?

The texture of your child’s lanugo hair may be drastically different than his terminal hair. That’s because, over time, the diameter of your child’s follicles enlarge as your child grows. And as the diameter changes, the shape of the follicle develops into its adult form.

The best way to picture this? Break out some pasta dough.

A pasta maker presses dough through holes to create different noodle shapes. For example, the hole shapes of a rotini maker will result in tight curling pasta, while a spaghetti maker will create thin, straight pasta. The shape of the pasta boils down to the shape of the hole the dough passes through.

Before your stomach starts to growl from this metaphor, turn your mind back to your child’s hair. Think of her follicles like a pasta-shaper. As the hair shaft (or “dough”) grows, the follicle shapes it into its unique texture, resulting in curls, waves, or straight strands.

Stanford University’s genetic department gives a general overview to follicle shape and the resulting hair strand:

• Round Follicles – If your baby’s follicles are perfectly round, she’ll have straight hair.
• Oval Follicles – The ovular shape of a follicle will cause the hair strand to grow in a “spiral” effect, resulting in curly hair.
• Somewhere in the Middle – A not-quite-oval and not-quite-circle follicle will result in a hair strand that grows halfway between curly and straight, creating wavy hair or kinky hair.

But what determines the shape of your child’s follicle? Or the thickness of each strand of hair?

Hair type is determined by genetics.

The Genetics of Hair Texture

Just like the color of your child’s eyes or the dimples in his cheeks, the texture of your baby’s hair depends on genetics. Follicle shape can be determined by a variety of different genes based on your child’s ancestry. Here are just a few genes that come into play, according to the US National Library of Medicine’s genetics center:

• EDAR – The EDAR gene is one of many genes that’s linked to thick, straight hair, especially within East Asian populations.
• FGFR2 – Along with the EDAR gene, the FGR2 gene is associated with hair texture and thickness.
• TCHH – Some scientists have theorized that the TCHH gene is related to differences in hair textures, particularly in people with northern European ancestry. This gene is also responsible for giving the body instruction on making trichohyalin, a protein found in hair follicles that links keratin molecules together to help make the hair shaft.

Dominant vs Recessive: An Oversimplification on Genes

When you think of genetics, you might think of Punnett Squares, a model of determining gene possibilities through dominant and recessive alleles. However, human genetics don’t quite fit into that tidy dominant-recessive box. In fact, Punnett Squares have proven to be an oversimplification of how many genes work.

Much like hair color, hair texture is polygenic—that means the texture of your baby’s hair is determined by the way multiple genes interact, not just one gene.

In conclusion, a baby’s hair texture undergoes several transitions, starting with the fine lanugo hair in utero to vellus hair and ultimately to terminal hair by around two years of age, influenced by genetics and the changing shape of hair follicles. It is a fascinating journey of growth and transformation, reflecting the complex interplay of biology and genetics, giving your child a unique hair texture that contributes to their individuality.

You might not know your baby’s hair texture yet, but you may find more answers than you ever thought possible with SneakPeek Test. Try our At-Home Early Gender Blood Test—the only at-home fetal sex test that can tell you whether you’re having a little boy or a little girl as early as 6 weeks into pregnancy.