It is common for hair to appear darker during pregnancy, a change that often surprises new mothers. This shift in color is a temporary, harmless side effect of the profound hormonal changes occurring throughout the body during gestation. The darkening effect is part of a broader increase in pigmentation that affects many women and will naturally reverse after the baby is born.
The Hormonal Mechanism Behind Hair Darkening
The primary driver of hair darkening is a surge in hormones, specifically estrogen and Melanocyte-Stimulating Hormone (MSH). Melanocytes are the cells responsible for producing melanin, the pigment that gives color to your hair, skin, and eyes. The placenta and pituitary gland increase MSH production during pregnancy, directly stimulating these melanocytes.
This hormonal stimulation causes melanocytes to increase their output of melanin pigment, which is then deposited into the hair shaft. Existing hair may appear darker, and new hair growth is often produced with a more concentrated color. This change is typically more pronounced in individuals who naturally have lighter hair or those with a genetic predisposition to pigmentation changes.
Related Skin Pigmentation Changes
The same hormonal mechanism responsible for darkening hair also causes noticeable pigmentation changes in the skin. Increased levels of MSH, estrogen, and progesterone stimulate melanocyte activity across the body, leading to hyperpigmentation.
One common manifestation is melasma, often referred to as the “mask of pregnancy,” which presents as dark, blotchy patches on the face. Another frequent change is the development of the linea nigra, a dark vertical line that runs down the center of the abdomen. These darkened areas, including the areolas and genitals, usually begin to fade after delivery as hormone levels return to their pre-pregnancy baseline.
Changes in Hair Texture and Growth Cycle
Beyond color changes, the high levels of estrogen experienced during pregnancy significantly affect the hair growth cycle. The elevated estrogen prolongs the anagen (growth) phase, keeping more hair strands in active growth for a longer period.
This extended growth phase results in less daily shedding, leading to the appearance of thicker, fuller hair, often described as the “pregnancy glow.” Some women also report a change in the physical texture of their hair, such as straight hair developing a wave or curly hair becoming straighter. These changes stem from the powerful influence of hormones on the hair follicle structure and cycle.
What Happens After Delivery
Once the baby is delivered, the body’s hormone levels, including estrogen and progesterone, drop rapidly. This swift decline signals the hair follicles to abruptly shift out of the prolonged growth phase. Consequently, a larger-than-normal percentage of hair strands simultaneously enter the resting and shedding phases.
This excessive shedding is known as postpartum telogen effluvium and typically begins about two to four months after childbirth. Fortunately, this hair loss is temporary, and the hair growth cycle usually normalizes within six to twelve months after delivery. The darkening of the hair and skin will also gradually reverse as the body resets in response to the normalized hormone environment.