AncestryDNA Traits
Almost all babies develop a healthy amount of fine, fuzzy hair on their faces, shoulders, and other body parts before birth. However, not all babies are born with that hair.
Whether your newborn baby's pictures boast a full head of hair or a bald scalp depends on genetics, environmental factors, and a protein named after a blue hedgehog in a popular video game. With an AncestryDNA + Traits test, you can discover whether you may have genes associated with hairiness in babies.
What's the Difference between a Newborn's Hair and Adult Hair?
The amount of hair you're born with actually has little bearing on how much hair you'll have as an adult. In fact, adult hair may even be a completely different shade or texture than the one you were born with. The hair that grows on an infant's head is called terminal hair. Terminal hairs are usually thicker and pigmented, though babies are often born with very fine strands, sometimes referred to as baby hair.
But before a baby develops terminal hair, babies grow a type of soft hair all over their bodies while in utero. This fine, soft hair, called lanugo, grows primarily on the face, back, shoulders, and ears. Growing lanugo is a normal part of fetal development, usually starting around three months into a pregnancy. Most babies shed it at around 37 weeks of gestation, but some newborns still have it.
Genetics and Baby Hair
While the vast majority of babies develop at least some hair in the womb, whether it sticks around at birth is often influenced by genetics inherited from the parents. Like most genetic traits, hair growth patterns in newborns are quite complex. Research analysis performed by the AncestryDNA team confirms this.
Curious to pinpoint how DNA impacts newborn hair, the team asked over 770,000 people, "How much hair did you have when you were born?" Respondents' answers, compared with their genetic profiles, revealed a substantial number of related DNA markers —over 3,800. The researchers developed a statistical tool, a polygenic risk score, to further contextualize these results. This particular tool allows scientists to predict whether someone has a specific trait based on their DNA. In this case, the amount of hair someone is born with appears to be at least 17% genetic.
What Else Can Affect a Baby's Hair?
Maternal hormone levels also affect a baby's hair growth. While in the womb, a fetus receives hormones from their mother that contribute to hair growth. In the weeks following birth, those maternal hormone levels plummet in the newborn, which causes the infant's hair growth to slow and the old hair to fall out.
Interestingly, the old wives' tale about heartburn during pregnancy and how much hair a baby will be born with likely has some degree of truth. Maternal hormone levels—higher estrogen and progesterone levels—influence pregnancy symptoms such as acid reflux and can cause heartburn. These hormones may also be associated with increased hair growth for the baby as they prolong the hair growth phase.
Additionally, since hair growth changes as a fetus develops, the timing of a baby's birth can impact how much hair they have. Prematurity can affect how hairy your newborn appears. Infants born before 37 weeks tend to have more lanugo since they haven't had a chance to shed it yet.
Interesting Facts About Baby Hair
The amount of lanugo during fetal development is affected by the "Sonic Hedgehog" (SHH) pathway. Named after the famous blue hedgehog, best known for going fast and collecting golden rings in video games, this pathway produces an integral protein for fetal development. The SHH pathway helps develop the brain, spinal cord, eyes, limbs, and lanugo.
Timing matters when determining how much hair a baby has at birth. Only around 30% of babies born through a normal pregnancy still have lanugo, so a premature birth can affect how hairy your newborn appears.
Hair loss in newborns can occur for several reasons. In fact, babies often lose a significant amount of hair from their heads during the first six months of life. While some lose it at a rate similar to growing it, others wind up completely bald.
Other babies may lose the hair on their heads to friction. Because babies sleep upwards of 19 hours per day in the earliest weeks, they may spend a lot of time with their heads in one spot. If they frequently turn their head left and right while sleeping, they may rub the hair right off their head and develop a bald spot on the back of the scalp known as friction alopecia. It's not permanent, and babies usually develop a full head of hair once they start sitting up and crawling more, typically after six months of age.
It's usually pretty easy to see where you got visible traits like earlobe type or hair color by looking at family photos. Temporary traits, like how much baby hair you were born with, however, are harder to see at a glance. If you're ready to see how much your newborn's hairdo may have been affected by genetics, take an AncestryDNA + Traits test today. If you've already taken an Ancestry origins test and you have an Ancestry membership, you can review your results today with your Ancestry subscription.
