The first months of a baby’s life are marked by big changes. But new parents might not expect to find clumps of hair on the crib mattress. After a few weeks, a baby with hair can become almost bald. Rest assured, this hair loss is rarely a problem.

Indeed, in most cases, hair loss in an infant is quite normal. It is linked to the changes experienced during childbirth, and to hormones like cortisol, which allow the baby to cope with the transition between the womb and the outside world.

The fetus begins to develop hair during the first trimester of pregnancy. Hair loss is simply a sign that the infant is adjusting to life outside the womb. In fact, on the head of an adult person, each hair goes through a phase of growth and a resting phase. When hair is not growing, it can easily fall out. This is a regular and well distributed cycle.

In the case of a newborn baby, the hormonal changes they go through during and after birth can cause all of the non-growing hairs to fall out at the same time. And for good reason, mother and baby undergo enormous changes during childbirth. As labor begins, the baby’s body begins to make hormones that help him or her grow and keep blood flowing after he or she separates from the umbilical cord.

Among these hormones is cortisol. Its role: to help the baby’s lungs mature and to promote the production of energy and heat in the infant. In adults, this stress hormone causes a fight-or-flight response, and also helps direct the body’s energy to vital functions. During childbirth, stress therefore triggers the production of cortisol in the baby, which in this way channels its energy to the elements essential for survival, leaving aside the superfluous… such as hair.

After birth, all of the baby’s hair remains in the resting phase until more resources are available. They tend to fall out when the baby is 8 to 12 weeks old, then grow back around 3 to 7 months old. But it will take until the child is 2 years old to see thicker hair appear.

The number and location of individual hair follicles is genetically determined. There is no point in shaving the baby’s head to stimulate hair regrowth. The color and thickness can also change several times in the first few months or years. All that’s left for parents to do is enjoy each different hair style, without getting too attached to them.

Elena Mars

Elena writes part-time for the Scientific Origin, focusing mostly on health-related issues.