Linea nigra: why a dark line appears on your bump

A brown line has appeared down the middle of your belly, and an auntie has already told you it means a boy.

It does not. The line has a name and a cause, and it fades on its own.

What it is

Linea nigra is Latin for "black line", which oversells it. The line is usually brown.

• Darker than the skin around it
• Running from your pubic bone up to your belly button, sometimes higher
• About half a centimetre to a centimetre wide
• Usually noticeable from the second trimester, around 20 weeks

It was there before you were pregnant, as the linea alba, or white line, too pale to see. Pregnancy hormones have simply coloured it in.

Why it appears

Rising oestrogen and progesterone make the pigment cells in your skin produce more colour.

The same process darkens other areas at the same time: your nipples and areolas, underarms, inner thighs, and existing scars and birthmarks. One cause, several changes.

It is very common. Cleveland Clinic puts it at up to about 80% of pregnant women, and it tends to be more visible on darker skin. Why it forms this particular line is still not fully understood.

It is harmless

The line is no problem for your pregnancy and none for your baby. It needs no medical attention.

For some women it is a source of self-consciousness, which is a fair reason to wish it gone. It is not a reason to worry about your health.

The myth

The idea that the line predicts your baby's sex, depending on whether it runs above your belly button, has no research behind it at all. It belongs with the ring-on-a-string test and reading the shape of your bump. Enjoy the guessing, and wait for the scan.

When it fades

Gradually, over the weeks and months after the birth, as your hormones settle. Many women find it has gone or nearly gone within a year.

It often comes back in a later pregnancy, sometimes earlier and darker. On deeper skin tones it can take longer to fade, because the contrast was stronger to begin with. That is normal, so there is no need to count the months against someone else's timeline.

The other darker patches

Once you know the cause, the rest of what your skin is doing makes more sense.

Darker nipples and areolas. Very common, and often the one change that does not fully reverse.

Darker underarms, groin and inner thighs. Same cause, and they fade the same way.

Moles and scars looking darker. Also normal. A mole that changes shape or outline, bleeds or itches is a different matter and worth showing a doctor.

Dark patches on your face. This is the same process on the part of you that gets the most sun, which is why your face needs daily sun protection when the line on your belly does not.

What to skip

Skin-lightening creams of unknown origin. They will not shift the line, the skin there is thin, and NPRA has repeatedly found creams sold in Malaysia containing mercury, hydroquinone and tretinoin. NPRA warns that mercury may interfere with the development of an unborn baby's brain.

Scrubbing. The colour is in the skin, not on it. Scrubbing only irritates, and irritated skin darkens more.

Lemon or lime juice. Citrus juice reacts with sunlight and can leave the area darker than before.

What you can do

Keep your belly out of strong sun. Sun is the one thing that reliably makes the line darker. Loose clothing over your bump at the pool or the beach is enough.

Keep the skin moisturised. Your bump is stretching anyway, and moisturised skin looks smoother and more even. If you already use our Stretch Mark Cream morning and night, the line is covered by the same routine. The Stretch Mark Serum, with niacinamide, helps skin tone look more even and helps reduce the look of dark spots, so it suits darker patches on the belly as well as stretch marks.

Protect your face every morning. Daily Protection Face Moisturizer SPF 20 PA++ moisturises and helps protect your skin against UVA and UVB in one step, with mineral UV filters. Reapply when you are outdoors.

All of these are formulated for pregnancy and breastfeeding. The line itself will fade after the birth whatever you put on it, so think of this as keeping your skin comfortable while you wait.