Some babies are born with a full head of hair, while others have little to no hair at all. So why do some babies start out with more hair than others? The answer likely involves genetics.
How it works
Babies are born with all the hair follicles they'll need in their lifetimes. On average, people come into this world with about five million hair follicles. Around week 10 of pregnancy, those follicles start growing tiny strands of hair called lanugo. By week 20, the scalp is covered with hair.But lanugo isn't the kissably soft stuff you see on a newborn's head. Lanugo is typically shed in the uterus around 24-28 weeks of pregnancy. This means that any hair a baby is born with likely started growing during the last trimester of pregnancy.
The genetic link
Genetics play a role in how much hair babies have at birth. 23andMe looks at 26 places in your DNA that influence how much hair you had at birth. There are other factors that may influence hair growth as well. Newborns with darker complexions often have more hair than babies with lighter skin, suggesting that genetics probably also plays a role.
Did you know?
Have you heard the saying about heartburn and baby hair? Throughout time, many people have believed that the amount of heartburn a woman has during pregnancy has something to say about the amount of hair her newborn may have. A lot of heartburn means a lot of hair, and vice versa. In 2006, some researchers decided to give this folktale a hard look, and they found out it might hold some truth after all. The mothers in the study who experienced moderate to severe heartburn were more likely to have babies with thick hair at birth.
Did you start out with lots of baby-soft hair or a couple of sweet little strands? 23andMe's Health + Ancestry Service can give you a closer look at the genetic variants that affect newborn hair. Pick up one of our kits to learn whether you're likely to have a lot of hair at birth based on your genetics.