學生時代,課本教的是5~6天.
百科全書寫:
http://en.wikipedia.org/wiki/Menstrual_cycle
『通常3~5天,但是2~7天也是被認為是正常的.』
原文如下:
Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal).[4] The average blood loss during menstruation is 35 millilitres with 10-80 mL considered normal;[5] many women also notice shedding of the endometrium lining that appears as tissue mixed with the blood. An enzyme called plasmin — contained in the endometrium — tends to inhibit the blood from clotting. Because of this blood loss, women have higher dietary requirements for iron than do males to prevent iron deficiency. Many women experience uterine cramps during this time. (Severe cramps or other symptoms are called dysmenorrhea.) A vast industry has grown to provide sanitary products to help women to manage their menses.