The dark line that appears down the middle of a pregnant belly is called the linea nigra, a harmless streak of skin darkening caused by pregnancy hormones. It typically becomes visible around 20 weeks (the second trimester) and runs vertically from the pubic bone to the belly button, sometimes extending further up toward the ribs. The line is about a quarter to half an inch wide and varies in color from light brown to nearly black depending on your natural skin tone.
Why the Line Appears
Everyone actually has this line already. Before pregnancy, it’s called the linea alba, Latin for “white line.” It’s a thin band of connective tissue running down the center of your abdomen where your left and right abdominal muscles meet. You can’t see it because it blends in with the surrounding skin.
During pregnancy, rising levels of estrogen and progesterone change how your skin produces pigment. Estrogen activates receptors inside skin cells called melanocytes, which are responsible for producing melanin, the compound that gives skin its color. When estrogen levels surge during pregnancy, these cells ramp up melanin production, darkening the skin along that midline strip. Scientists previously believed a hormone from the pituitary gland (melanocyte-stimulating hormone) was responsible, but that theory has since been overturned. The primary driver is estrogen, with progesterone amplifying the effect.
Who Gets It and When
Most pregnant people develop a visible linea nigra. It tends to show up around the 20-week mark, though some notice it earlier and others later. People with darker skin tones generally see a more prominent line because their melanocytes are already producing more melanin at baseline, so the hormonal boost creates a more noticeable contrast. If you have lighter skin, the line may appear faint or barely visible.
There’s no way to predict exactly how dark yours will become. Some people see a subtle tan streak, while others develop a line dark enough to be visible through thin clothing. The line often deepens as pregnancy progresses and hormone levels continue to climb.
Other Skin Changes From the Same Cause
The linea nigra isn’t the only place your skin darkens during pregnancy. The same hormonal mechanism can darken your nipples and areolas, the skin around your underarms, and the inner thighs. Some people also develop melasma, sometimes called the “mask of pregnancy,” which creates brown or gray-brown patches on the cheeks, forehead, nose, and upper lip. Sun exposure and heat can intensify all of these changes because ultraviolet radiation triggers melanocytes to produce even more pigment on top of the hormonal increase already in play.
Wearing sunscreen on exposed skin, particularly the face, can help limit additional darkening from sun exposure. This won’t prevent the linea nigra itself (it’s covered by clothing most of the time), but it’s useful for managing melasma and other pigmentation changes on areas that get direct sunlight.
Does the Line Predict the Baby’s Sex?
One persistent folk belief claims the line’s length reveals whether you’re having a boy or a girl. The myth goes like this: if the line extends only from the pubic bone to the belly button, it’s a girl; if it reaches all the way up past the belly button toward the ribs, it’s a boy. There is no scientific basis for this. The length and darkness of the line are determined entirely by your hormonal levels and individual skin pigmentation, not by the baby’s sex. It’s one of many gender prediction tales passed down through oral tradition, fun to talk about but not reliable in any measurable way.
Does It Go Away After Pregnancy?
The linea nigra fades on its own after delivery as hormone levels return to their pre-pregnancy baseline. For most people, it gradually lightens over several months postpartum. The timeline varies. Some see it nearly disappear within a few months, while others notice a faint trace for a year or longer. If you breastfeed, the line may take a bit longer to fade because breastfeeding keeps certain hormone levels elevated.
In some cases, the line never fully returns to its original invisible state, leaving behind a very faint mark. This is more common in people with darker skin. There’s no medical treatment needed for it, and bleaching creams are not recommended during pregnancy or breastfeeding. If the line persists well after you’ve stopped breastfeeding and it bothers you, a dermatologist can discuss options at that point.
What to Know About Prevention
You can’t prevent the linea nigra from forming. It’s a normal physiological response to the hormones your body needs to sustain a pregnancy. Some sources suggest that adequate folic acid intake may help moderate skin darkening, since folate deficiency has been loosely associated with increased pigmentation, but there’s no strong clinical evidence that supplementation will keep the line from appearing. That said, folic acid is already a standard part of prenatal care for other critical reasons, so you’re likely taking it regardless.
Trying to scrub, exfoliate, or lighten the line during pregnancy is unnecessary and unlikely to work. The darkening comes from deep within the skin cells, not from the surface layer. The most practical approach is simply knowing what it is, understanding that it’s temporary, and letting it fade naturally after your baby arrives.