審定稿：https://en.wikipedia.org/wiki/Wikipedia:WikiProject_Medicine/Translation_task_force/RTT/Simple_menstruation
中文：https://zh.wikipedia.org/wiki/%E6%9C%88%E7%B6%93
Figure showing the progression of the menstrual cycle and the different hormones contributing to it.
Menstruation, also known as a period or monthly,[1] is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina.[2] Up to 80% women report having some symptoms prior to menstruation.[3] Common symptoms include acne, tender breasts, bloating, feeling tired, irritability, and mood changes.[4] These symptoms interfere with normal life and therefore qualify as premenstrual syndrome in 20 to 30% of women. In 3 to 8%, they are severe.[3]
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’’’月經’’’（{{lang-en|menstruation, period, monthly}}[1]），係指血液或[[黏膜]]定期從{{link-en|子宮內膜|Endometrium}}經[[陰道]]排出體外的現象[2]。高達80%女性曾表示在月經開始前出現部分症狀[3]。常見症狀包含長出[[粉刺]]、乳房變得柔軟、感到疲憊、容易發怒與情緒改變[4]。由於這些症狀會干擾正常生活，因此被稱為[[經前綜合症]]；20-30%女性會得到此症，其中的3-8%則較為嚴重[3]。
The first period usually begins between twelve and fifteen years of age, a point in time known as menarche.[1] They; however, may normally start as early as eight.[2] The average age of the first period is generally latter in the developing world and earlier in developed world. The typical lenght of of time between the first day of one period and the first day of the next is 21 to 45 days in young women and 21 to 31 days in adults (an average of 28 days).[5][2] Menstruation stops occuring after menopause which usually occurs between 45 and 55 years of age.[6] Bleeding usually lasts around 2 to 7 days.[2]
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月經通常在12-15歲之間首次出現，該次月經被稱做[[初潮]][1]；然而，初潮可能會提早於8歲出現[2]。[[已開發國家]]的初潮平均年齡比[[開發中國家]]還早。從一段經期開始到下一段經期開始的間隔（月經週期），在青少年女性時期為21-45天，在成年女性則為21-31天，平均約為28天[2,5]。月經在[[更年期]]後結束，通常發生於45-55歲時[6]。月經來臨時，經血會持續流出約2-7天[2]。
The menstrual cycle occurs due to the rise and fall of hormones. This cycle results in the thickening of the lining of the uterus and production of an egg which is required for pregnancy. The egg is realeased around day fourteen in the cycle and the thickened lining of the uterus is to provide nutrients for a potential developing baby. If pregnancy does not occur, the lining is released in what is known as menstruation.[2]
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[[月經週期]]的發生與體內[[激素]]濃度的高低有關。月經週期間，為了做好懷孕的準備，子宮內膜會增厚，同時會排出[[卵子]]。卵子大約是在月經週期的第14天被釋出，同時間，用來提供[[營養素|養分]]的子宮內膜也已經變厚，準備讓胚胎著床[[妊娠|發育]]。如果懷孕並未發生的話，子空內膜將會崩解，形成月經[2]。
A number of problems with menstruation may occur. A lack of periods, known as amenorrhea, is when periods do not occur by age 15 or have not occured in 90 days. Perioids also stops during pregnancy and typically do not resume during the initial months of breastfeeding. Other problems include painful periods and abnormal bleeding such as bleeding between periods or heavy bleeding.[2] Menstruation also occur in some other animals including shrews, bats, and other primates such as apes and monkeys.[7]
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部分身體上可能會出現的問題，起因在於月經。[[閉經|無月經症候]]的定義，是指當女性滿15歲還沒有初經，或是連續90天都沒有出現月經。經期在[[懷孕]]期間會暫時停止，甚至[[母乳餵養|哺乳]]初期的幾個月也都還不會出現。其他月經相關的病症：像是[[經痛]]、[[功能失調性子宮出血|非經期的不正常出血]]或是異常的大量出血[2]。除了人以外，部分的生物像是：[[鼩鼱科|鼩鼱]]、[[蝙蝠]]和[[靈長類]]的[[猿]]與[[猴]]也都有{{link-en|月經 (哺乳類)|月經}}週期[7]。
原始中文內容 (待整合)
月經是指子宮內膜脫落，脫落的內膜組織和血液由陰道排出的現象[1]，流出的血液稱為經血。月經在民間有多種俗稱，如：好朋友、大姨媽[2]，等等。女性及部分雌性哺乳動物在生育期內會固定出現月經，此循環週期稱為月經週期。一般情況下，女性一次月經的出血量在30毫升至80毫升之間。
女性第一次月經來潮稱為初經（月經初潮），代表青春期的開始，女性在懷孕期間並不會有月經。哺乳期間依哺乳情形，可能會有一段閉經的期間（泌乳停經法）[3]，更年期之後月經就會停止。