Pregnancy changes skin pigment in a way almost nobody is warned about, and the two most visible results — a dark line down the bump, and patches on the face — share one cause and one useful response.
The short answer: pregnancy hormones stimulate the cells that produce pigment. That produces linea nigra down the abdomen, melasma on the face, and darkening of the areolas, moles and freckles. Melasma is driven by sun exposure on top of the hormonal change, so daily broad-spectrum sunscreen is the intervention that actually works — and it prevents far better than anything treats. Most of it fades after birth. A mole that is changing needs looking at regardless of the pregnancy.
Why it happens
Melanocytes — the cells that make pigment — become more active in pregnancy. Oestrogen and progesterone both stimulate them, and the effect is not uniform across the body: it concentrates where pigment is already relatively higher, or where there is friction or sun exposure. That is why the areolas darken, why existing moles get darker rather than new ones appearing, and why the linea alba becomes the linea nigra without anything new being created.
Melasma adds a second driver. Ultraviolet light stimulates the same cells directly, so the areas of the face most exposed to it — cheeks, forehead, upper lip — develop patches. The hormonal change makes those cells more reactive; the sunlight is what sets them off. That is why two people with identical hormone levels can have entirely different amounts of it, and why sunscreen is not a token gesture here.
What is normal
| Normal pregnancy change | Get it looked at | |
|---|---|---|
| Moles | Existing ones darken, evenly | One changes shape, outline or colour, or itches, bleeds or crusts |
| Patches | Symmetrical, on both cheeks or across the forehead | One-sided, raised, growing, or ulcerated |
| Line | Vertical dark line on the abdomen | — |
| Lumps | Small soft skin tags in friction areas | A firm lump that keeps growing, or a sore that will not heal |
| Itch | Mild, over a stretching bump | Intense itching, especially palms and soles, with no rash — same-day call |
Call the same day if you have intense itching, particularly on the palms of your hands and soles of your feet, especially worse at night and with no rash to see. That is how intrahepatic cholestasis of pregnancy presents, it is diagnosed with a blood test, and it is not a skin condition at all. The stretch marks page covers the distinction.
What actually helps
☀️ In order of effect
- Broad-spectrum sunscreen every day, including in winter and on cloudy days, reapplied. Mineral filters — zinc oxide, titanium dioxide — are the usual recommendation in pregnancy and also block visible light, which contributes to melasma.
- A wide-brimmed hat and shade. Sunscreen is not a substitute for not being in it.
- Azelaic acid or niacinamide if you want to treat pigmentation during pregnancy — both are generally considered suitable. See the acne page for the wider safe list.
- Hydroquinone, retinoids and strong chemical peels — the mainstays of melasma treatment outside pregnancy — are avoided during it, and hydroquinone is also generally avoided while breastfeeding.
- Wait before treating. Much of it fades in the months after birth, and treating too early means treating something that was leaving anyway.
Skin changes in pregnancy — at a glance
Oestrogen and progesterone stimulate melanocytes, so pigment increases where it is already relatively high or where there is friction or sun: the areolas and genital skin darken, existing moles and freckles deepen, skin tags appear in friction areas, and the linea alba becomes the visible linea nigra, usually from the second trimester. Melasma — symmetrical brown patches on the cheeks, forehead, upper lip or jaw — has a second driver in ultraviolet and visible light, which is why daily broad-spectrum sunscreen with a mineral filter, reapplied, plus a hat and shade, is the only intervention that reliably changes the outcome, and why prevention massively outperforms treatment. Azelaic acid and niacinamide are suitable during pregnancy; hydroquinone, retinoids and strong peels are not, and belong to a conversation after birth. Most changes fade substantially over the months following delivery. A single mole changing in size, shape, outline or colour, or itching, bleeding or crusting, needs assessing whatever the pregnancy is doing — and intense itching of palms and soles with no rash is cholestasis, not a skin change, and needs a same-day call.
Inside Baby Novum: bump photos and diary entries are stored with their date and gestational week, so "has this changed since week 20?" becomes a question with an answer rather than a guess. Photos and entries are encrypted on the device with a hardware-backed key, with no account and no server holding a copy.
Frequently Asked Questions
What is the dark line on my stomach?
Linea nigra — a vertical line of darker skin running from the pubic bone towards the navel and sometimes above it. The line was always there as the linea alba, a band of connective tissue where the abdominal muscles meet; pregnancy hormones simply increase pigment production along it so it becomes visible. It typically appears in the second trimester and fades over the months after birth, though it may not disappear completely.
What is melasma and can I prevent it?
Melasma — sometimes called chloasma or the "mask of pregnancy" — is symmetrical brown or grey-brown patches, usually on the cheeks, forehead, upper lip or jawline. It is driven by pigment-producing cells responding to hormones, and sun exposure is the main aggravating factor. Daily broad-spectrum sunscreen, reapplied, plus a hat, is the one intervention that reliably reduces how much develops. It is much easier to prevent than to treat.
Do skin changes in pregnancy go away?
Most fade substantially in the months after birth as hormone levels return to normal. Linea nigra usually lightens considerably. Melasma often improves but can persist, particularly with continued sun exposure or while breastfeeding. Treatments exist for persistent melasma, but several of them — including hydroquinone and retinoids — are not used during pregnancy or breastfeeding, so they belong to the conversation afterwards.
What other skin changes are normal in pregnancy?
Darkening of the areolas, the genital skin and existing moles and freckles. Skin tags, particularly in areas of friction such as the neck, under the breasts and in the armpits. More visible veins. A darker line or patches as above. And stretch marks, which are a separate mechanism — collagen and elastin under tension rather than pigment.
When should I get a skin change checked?
A mole that changes — in size, shape, colour, outline, or that starts itching, bleeding or crusting. Pregnancy darkens moles generally, and that is not a reason to ignore a single one that is behaving differently from the others. Also worth showing someone: any new lump that is growing, an ulcer that will not heal, and any widespread itchy rash, or intense itching with no rash at all, which is a different and more urgent question.