Linea nigra (Latin for "black line"), often referred to as a pregnancy line, is a linear hyperpigmentation that commonly appears on the abdomen. The brownish streak is usually about a centimeter (0.4 in) in width. The line runs vertically along the midline of the abdomen from the pubis to the umbilicus, but can also run from the pubis to the top of the abdomen.
For pregnant women, linea nigra is attributed to increased melanocyte-stimulating hormone made by the placenta, which also causes melasma and darkened nipples. Fair-skinned women show this phenomenon less often than women with darker pigmentation. Linea nigra typically disappears within a few months after delivery.
Although linea nigra is rarely discussed outside pregnancy, males and females of all ages may have it. Except in pregnancy, both sexes have highest and equal prevalence of linea nigra from age 11 to 15. This increase in prevalence could be the result of hormonal changes during puberty. After age 15, the prevalence of linea nigra in males declines. In females it is often just a sign of unusually high benign estrogens. The prevalence for both sexes drops to below 10% after age 30. Additionally, it can appear after a short-interval weight gain. It may also be a sign of hormonal imbalance, genetic disease, cancer, inflammation and even fungal infection.
- Okeke, Linus Ikechukwu; George, Adekunle Olufemi; Ogunbiyi, Adebola Olufunmilayo; Wachtel, Mitchelle (November 2012). "Prevalence of linea nigra in patients with benign prostatic hyperplasia and prostate carcinoma". International Journal of Dermatology. 51: 41–43. doi:10.1111/j.1365-4632.2012.05564.x. ISSN 0011-9059. PMID 23210957. S2CID 21882972.
- She Knows Network: "What's that line? All about linea nigra" Archived 2008-02-20 at the Wayback Machine
- Heffner, Linda (2010). The Reproductive System at a Glance. Wiley-Blackwell. pp. 51. ISBN 978-1-4051-9452-5.
- Pregmed, Editor (2014-11-15). "Linea nigra and pregnancy". Pregmed. Archived from the original on 22 February 2015. Retrieved 22 February 2015.
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- Olufemi, George, Adekunle Olufemi Shittu, Olayiwola Babatunde Enwerem, Eokezie Wachtel, Mitchell Kuti. The incidence of lower mid-trunk hyperpigmentation (linea nigra) is affected by sex hormone levels. National Medical Association. OCLC 678245464.
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