Linea nigra is a common symptom of pregnancy that begins to be evident at about the beginning of the second trimester. The term is derived from the Latin and translates as black line, but this translation isn’t that useful or descriptive for pregnant women. Instead the linea nigra can be described as a thin, dark line that usually begins just above the pubic hair in the center and runs up to the belly button or beyond it. Not all women get a linea nigra when they’re pregnant, but many of them do, and some may retain it after pregnancy, thought most other times the line eventually fades.
Some women have a precursor to the linea nigra called a linea alba. A light line, sometimes paler than the skin, can be seen where the dark line could eventually form. What happens next for many women is that the skin produces too much pigment called melanin and this results in a dark line forming. There are actually several theories on why women get this, but the one most adopted is that increase in hormonal production at this time sends melanin into hyperdrive. This is readily proven by other skin discolorations that can occur during pregnancy like the butterfly mask that may occur over the face, or the darkening of nipple, genitals and moles, which is common.
It’s also known that a linea nigra is much more likely to occur in women of darker skin coloration because they have extra melanin at the onset. Formation of the line is that much easier and hyperpigmentation can occur more readily. Yet, there are many light-skinned women who will also develop this pigment issue.
Most women are concerned that a linea nigra will never disappear after pregnancy is over, but the majority of women will see the skin lighten up again. This is not always immediate, is likely to take longer in darker-skinned women, and might not mean a total return to the skin color that existed before the line formed. Some people notice the line turns back into a linea alba. It should also be noted that sun protection is very much required to keep the line light; exposure to the sun or tanning may result in it becoming darker or more apparent.
There is a considerable amount of folk wisdom and old wives knowledge surrounding appearance of this line and gender. Though unreliable, darker lines are thought to indicate women are carrying boys. Alternately, lines that stop at the belly button were thought to mean that the developing baby is a girl. While useful in theory, there’s little proof that a linea nigra indicates gender through its appearance.