Linea nigra (pregnancy line)

What is the linea nigra?

Linea nigra is a condition in which pregnant women experience a darkening (hyperpigmentation) in the midline of the abdomen. It is typically a thin line of darker coloured skin that extends from the belly button (umbilicus) downwards towards the pubic hair but may also extend upwards to just below the ribs (xiphoid process). The line always runs vertically in the midline of the abdomen.

The darkening is due to increased pigmentation of a ligament, the linea alba (white line) that exists in this area. When it becomes darkened, it is then referred to as the linea nigra (dark line).

Am I likely to have a linea nigra?

Approximately 90% of pregnant women will experience some form of skin darkening (hyperpigmentation) during their pregnancy.

Women who are dark haired and have dark complexions are more likely to develop linea nigra, and it is also more likely to be more pronounced in these women also.

Why does it occur?

The exact cause is not known but it is thought to occur due to increased levels of hormones in pregnancy. These include:

• Melanocyte stimulating hormone – a hormone that stimulates melanocytes – the cells in the body that produce pigment and give rise to darker skin, freckles, birthmarks (naevi) etc.;
• Oestrogen; and
• Progesterone.

When does it occur?

Linea nigra tends to first occur in the first trimester of pregnancy and it is considered as one of the earliest signs of pregnancy.

However, in first pregnancies its appearance may be delayed until several months into the pregnancy.

How long does the linea nigra last?

The increased pigmentation of the linea alba to form the linea nigra usually progresses during the pregnancy until delivery.

The linea nigra almost always lightens following delivery of the baby, however, in some women it will not completely fade.

In subsequent pregnancies it may appear earlier and darker than previously.

What can I do about the linea nigra?

The linea nigra will generally fade following the delivery of your baby. Preventative measures and treatment options are limited.

It is recommended that pregnant women wishing to minimise skin darkening use sunscreen on sun exposed areas, wear appropriate protective clothing, avoid sunbathing and excessive sun exposure. Current Australian skin cancer prevention campaigns recommend that individuals use sun protection such as hats, clothing, sunscreen, sunglasses and/or shade during periods when UV index is high, typically between 10am and 3pm. Given that the sun is a major source of Vitamin D, essential for bone health, there needs to be a balance between exposure and protection. The amount of sun exposure you need to prevent Vitamin D deficiency varies depending on your skin type, location, season and time of day. Generally 30 mins of sun exposure to the neck, hands and arms when the UV index is low gives sufficient exposure to maintain Vitamin D levels for Australians. This is something that you can discuss with your General Practitioner as it will also vary depending on your individual risk factors for skin cancer and vitamin D deficiency.

Kindly written and reviewed by Dr Allison Johns  BSc (Hons) MBBS, Doctor at King Edward Memorial Hospital and Editorial Advisory Board Member of Parenthub and Virtual Medical Centre.

References

1. Adekunie OG, Olaylwala BS, Eokezie E, Mitchell W, Olufemi K. The Incidence of lower mid-trunk hyperpigmentation (linea nigra) is affected by sex hormone levels. Journal of the National Medical Association 2005; 97: 685-688. (Full text)
2. Beischer NA, Wein P. Linea Alba Pigmentation and Umbilical Deviation in Nulliparous Pregnancy: The ligamentum Teres Sign. Obstetrics and Gynecology 1996; 87:254-256. (Abstract)
3. Black, M (ed). Obstetric and Gynaecologic Dermatology. 3^rd Edition. 2008. Elsevier, China.
4. Ingber, A. Obstetric Dermatology: A practical guide. 2009. Springer-Verlag, Berlin Heidelberg. (Book)
5. Stalgis-Bilinski KL, Boyages J, Salisbury EL, Dunstan CR, Henderson SI, Talbot PL. Burning daylight: balancing vitamin D requirements with sensible sun exposure 2011; 194:345-348.  (Full text)