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When babies are born, many new parents may notice fine, soft body hair covering their little ones. This hair, known as lanugo, is a completely normal and temporary feature of infant development. In fact, most babies are born with it—though the amount can vary greatly from one infant to another.
Lanugo, which derives from the Latin word lana meaning “wool,” is a fine, downy body hair that covers the fetus around the third month of pregnancy. This hair is most prominent in premature babies, who may not have had enough time to shed it in the womb before birth. While lanugo might appear quite thick in some infants, it typically disappears within a few weeks after birth.
The Development of Lanugo
In the early stages of pregnancy, lanugo begins to develop on the fetus’s body. By the seventh month of pregnancy, this fine hair covers most of the baby’s skin, except in areas where hair follicles don’t form. Interestingly, although not every baby is born with lanugo, all babies had it at some point in utero. Typically, it begins to shed around 33 to 36 weeks of pregnancy, mixing with amniotic fluid and being ingested by the baby. This mix of lanugo and amniotic fluid is then passed through the baby’s system and forms part of the first bowel movement, known as meconium.
However, for babies born prematurely, the lanugo may not have had a chance to fully shed, leaving them with more noticeable body hair at birth. Once the vernix—a white, waxy substance that covers a newborn’s skin—begins to fade, small amounts of lanugo may remain for several weeks, gradually disappearing on its own.
Is Lanugo Linked to Heartburn During Pregnancy?
A long-standing belief among some expectant mothers is that experiencing heartburn during pregnancy could lead to babies being born with more hair. A 2006 study in the United States found that women who reported moderate or severe heartburn were more likely to give birth to babies with above-average amounts of hair. While the exact cause of this correlation is still debated, researchers suggest that pregnancy hormones may play a role, both in relaxing the lower esophageal sphincter (causing heartburn) and in stimulating fetal hair growth.
Further research in Thailand in 2012 also suggested a link between maternal heartburn and a higher incidence of babies born with more hair, though more studies are needed to confirm this connection definitively.
Genetic and Ethnic Factors in Lanugo
Just as every baby’s hair growth pattern is unique, so too is the presence of lanugo. Factors like genetics and the baby’s ethnicity can influence how much lanugo is visible at birth. For instance, babies with darker complexions tend to have darker lanugo, which may be more noticeable. In contrast, babies with lighter skin often have lighter or colorless lanugo. While there is no need to worry about the presence of lanugo, its appearance can vary greatly among babies.
What Is the Purpose of Lanugo?
While lanugo is temporary, it serves an important role in the development of the fetus. It helps regulate the baby’s body temperature and binds with the vernix to protect the baby’s sensitive skin. Vernix plays a crucial role in keeping the skin from losing water, helps protect against infections, and aids in the overall development of the baby’s skin barrier.
When Does Lanugo Go Away?
For the vast majority of babies, lanugo will begin to fade away within a few weeks after birth. It is completely normal for some babies to retain a small amount of lanugo for a short time. After the first few months, the lanugo on the baby’s head will be replaced by the permanent hair, which starts to grow and lengthen.
In some rare cases, infants may develop excessive lanugo due to a genetic condition called hypertrichosis lanuginosa, which results in an abnormal amount of body hair. This condition may either be present at birth or develop later, triggered by a health condition, certain medications, or eating disorders.
Conclusion
Lanugo is a perfectly natural and temporary part of newborn development. While some babies may appear especially “hairy” at birth, parents need not worry—this fine body hair will typically disappear within the first few weeks of life. Whether a baby has a little or a lot of lanugo, it is simply one of the many features that mark the baby’s growth and development. And while the connection between heartburn and hair growth remains somewhat uncertain, one thing is clear: lanugo is nothing to be concerned about. It’s just one of nature’s ways of preparing babies for life outside the womb.
