Babies are born with varying amounts of hair, from infants with a full, thick mane to those who appear completely bald. The simple visual answer is often no, but the biological answer is complex, rooted deep within fetal development. To understand the variability seen at birth, it is necessary to explore the prenatal timeline of hair growth, the distinct types of hair produced in the womb, and the inevitable shedding cycle that follows delivery. The presence or absence of hair at birth depends entirely on where a baby is in this continuous cycle of fetal hair production and replacement.
Hair Development Before Birth
The process of hair formation, known as folliculogenesis, begins early in pregnancy. Hair follicles start to develop around the ninth week of gestation, originating from the ectoderm layer of the embryonic skin. This development proceeds in a cephalocaudal direction, meaning it starts on the head and then moves downward toward the rest of the body. By the 14th to 15th week of gestation, tiny hair buds emerge through the skin, establishing the baby’s future hairline. The initial hair that grows from these newly formed follicles is a specialized type designed for the environment of the womb.
The Difference Between Lanugo and Vellus Hair
The first hair to grow on a fetus is called lanugo, a fine, soft, and typically unpigmented downy hair. Lanugo usually appears around the 16th to 21st week of pregnancy and covers nearly the entire body, often concentrated on the forehead, shoulders, and back. This fetal hair serves a functional purpose by anchoring the vernix caseosa, a thick, white, waxy substance that coats the fetal skin. Vernix protects the delicate skin from constant exposure to amniotic fluid, preventing chafing and water loss.
Lanugo is part of the first hair cycle and is normally shed into the amniotic fluid between 33 and 36 weeks of gestation, often contributing to the baby’s first stool, called meconium. As the lanugo sheds, it is replaced by vellus hair, which is also fine and light but is shorter and less noticeable. Vellus hair is the type of hair that covers much of the body in childhood and adulthood.
What Happens to Newborn Hair After Birth
The amount of hair a baby has at birth is highly variable, depending on the precise timing of the lanugo shedding cycle. If lanugo was shed in the womb, the baby may appear bald or have sparse vellus hair; if shedding had not yet occurred, they may be born covered in fine, downy lanugo. A significant change in hair density and texture is expected in the first few months of life.
This universal shedding is often due to telogen effluvium, triggered by the sudden drop in pregnancy hormones after birth. During pregnancy, high levels of these hormones influenced the baby’s hair follicles, causing a large number of them to enter the growth phase, or anagen. Once the hormonal influence is removed, these follicles simultaneously transition into the resting phase, called telogen, which leads to mass shedding. The hair loss usually peaks around two to three months of age and is a normal part of the hair cycle reset. The hair that falls out is eventually replaced by new hair, which can often be different in color and texture than the original newborn locks. The duration of this process varies, with some babies growing a full head of new hair by six months, while for others it may take up to a year or longer.