A baby’s hair development often fascinates new parents, leading to questions about its appearance and changes. Understanding the typical stages of hair growth, from before birth through infancy, clarifies what to expect. Infant hair development follows a predictable, yet varied, pattern influenced by several factors.
Hair Growth Before Birth
Hair development begins early, while the baby is still in the womb. Hair follicles start forming on the scalp and body around 14 weeks of gestation, with hair beginning to grow shortly after. By approximately 16 weeks, a fine, soft, unpigmented hair known as lanugo appears across the fetus’s body.
Lanugo serves a purpose in fetal development, helping to anchor the vernix caseosa, a protective, waxy substance, to the skin. This helps protect the delicate fetal skin from amniotic fluid and aids in temperature regulation. Most lanugo is shed between 33 and 36 weeks of gestation, often consumed by the fetus as it drinks amniotic fluid, contributing to the first bowel movement after birth. After lanugo sheds, it is replaced by vellus hair, which is thinner and less visible.
Hair at Birth
At birth, a baby’s hair can vary significantly in amount, color, and texture. Some newborns arrive with a full head of hair, while others may have very little or appear nearly bald. This wide range is normal, and the initial hair does not necessarily indicate what the child’s hair will look like later in life.
While most lanugo is shed before birth, some babies, particularly those born prematurely, may still have visible lanugo on their bodies. This fine, downy hair will fall out within the first few weeks after birth. The presence or absence of hair at birth, and its characteristics, are largely influenced by genetics, hormones, and ethnicity.
Common Hair Changes After Birth
Many babies experience infant hair loss, also known as neonatal alopecia, within their first few months. This shedding usually peaks around two to three months of age and is a normal process. This type of hair loss, called telogen effluvium, occurs because hormonal shifts after birth cause a larger number of hair follicles to enter the resting phase simultaneously.
The hair that grows back after this initial shedding may differ significantly in color and texture from the hair a baby had at birth. For example, a baby born with dark hair might develop lighter hair, or straight hair could become curly. This new hair is referred to as terminal hair, which is thicker and stronger than the initial vellus hair. Additionally, a bald spot on the back of the head is common due to friction from lying down, and this typically fills in as the baby becomes more mobile.
Another common condition affecting a baby’s scalp is cradle cap, medically known as seborrheic dermatitis. It appears as scaly, greasy, or crusty yellow or white patches on the scalp, and sometimes on other areas like the face or behind the ears. While it can look concerning, cradle cap is generally harmless, not itchy, and usually resolves on its own within the first year of life. It is believed to be related to an overproduction of skin oil and a type of yeast, possibly influenced by maternal hormones.
Influences on Baby Hair
A baby’s hair characteristics are determined by a combination of factors, with genetics playing a significant role. The hair’s color, texture, and density are largely inherited traits passed down from both parents. Genes influence the hair growth cycle and the production of proteins like keratin, which determine hair strength and structure.
Hormones also influence hair development, particularly the hormonal environment during pregnancy and the fluctuations after birth. These hormonal shifts contribute to the initial hair loss many infants experience. While less direct, a mother’s nutrition during pregnancy and the baby’s nutrition post-birth can also play a part in overall hair health and development.