The sight of a newborn covered in a fine layer of hair can be startling for new parents, but this observation is common and indicates a normal stage of development. This fine hair, which is a temporary part of the fetal experience, is not a cause for alarm and will almost certainly resolve on its own in the coming weeks. Learning about the origins and function of this hair helps to understand why it is present at birth.
Understanding Lanugo
The specific hair observed on a newborn is called lanugo, a term derived from the Latin word for wool. Lanugo is characterized by its soft, fine, and downy texture, appearing like a delicate coating on the baby’s skin. This hair can be unpigmented or range from light to dark, sometimes making it more noticeable on infants with darker complexions.
While lanugo can grow anywhere with a hair follicle, it is most often visible across the shoulders, the upper back, and the ears. It may also appear on the forehead and down the tailbone. All babies develop this hair in the womb, but only about 30% of full-term infants retain remnants of it at birth.
The amount of lanugo correlates with gestational age. Infants born prematurely are more likely to have a noticeable amount of this hair covering their bodies. Its presence at birth signifies the baby arrived before the natural shedding process was fully completed.
Why Lanugo Develops
Lanugo develops around the fourth or fifth month of pregnancy and serves several functions for the growing fetus. One of its main roles is to aid in thermoregulation, providing a layer of insulation for the baby. This is important because the fetus has not yet developed enough body fat to effectively regulate its own temperature.
The hair also provides an anchor for the vernix caseosa, a thick, white, waxy substance that coats the baby’s skin in the womb. Lanugo helps this protective layer adhere to the skin, preventing water loss and shielding the delicate skin from the amniotic fluid that surrounds the baby. Without the vernix, the baby’s skin could become chapped or damaged by prolonged exposure to the fluid.
Beyond insulation and protection, the interaction between the lanugo and the vernix may also play a part in promoting fetal growth. The movement of the hairs in the amniotic fluid is thought to activate sensory receptors on the skin. This activation may help stimulate the release of hormones that support healthy development.
The Shedding Timeline
Most fetuses shed the majority of their lanugo hair while still in the womb, typically between 33 and 36 weeks of gestation. The shed hairs mix with the amniotic fluid and are often swallowed by the baby, becoming a component of the baby’s first stool, known as meconium.
For babies born with lanugo still present, the hair begins to fall out shortly after birth. This process usually occurs within the first few weeks of life, though it can take up to a few months to fully disappear. The soft hair is gradually replaced by vellus hair, the finer and lighter “peach fuzz” that covers the skin of children and adults.
Parents should avoid scrubbing or attempting to remove the lanugo. Harsh rubbing can irritate the baby’s sensitive skin and will not hasten the natural timeline.
When to Consult a Pediatrician
In the vast majority of cases, lanugo disappears completely within the first few months. However, persistent or changing hair growth should be discussed with a healthcare provider. If the fine hair remains on the baby for many months, or if the hair begins to grow thicker and coarser, it warrants a consultation. A doctor can evaluate the hair’s quality and distribution to rule out rare underlying conditions, such as certain endocrine or metabolic issues.