What Is A Normal Cycle?
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Most women have one menstrual cycle every 22 to 35 days. Day 1 is the first day you bleed. Day 1 should be the day when the heaviest bleeding occurs. Bleeding should last only 4 to 6 days.
A few women have a regular cycle of 18 to 40 days, and if that is consistent, fairly painless, and not excessively heavy or light, then it is considered a normal variation.
Eighty percent of bleeds last three to six days, which indicates an ovulatory cycle, during which an egg was released for fertilization. Bleeds lasting longer than eight days indicate dysfunctional ovaries. The problem could be anovulation, meaning no egg was released by the ovary for fertilization, or inadequate hormones in the second half of the cycle (luteal phase). Progesterone is supposed to be dominant in the second half.
Quantity
Normal blood loss is 10 to 35 ml, or 2 to 7 soaked sanitary pads per cycle. The absolute maximum blood loss during a heavy cycle should be 45 to 60 ml. If it exceeds this amount, the woman is at risk of developing iron deficiency anemia and will have a difficult pregnancy.
The mean blood volume lost during menstruation is 43.4 milliliters (1.46 ounce). However, the range in 80% of women is 10 mL (1/3 ounce) to 84 mL (2.84 ounce). The type of birth control used influences blood loss. Women on The Pill lose less blood. Women using IUDs lose more blood. The upper limit of normal menstrual blood loss is 80 mL per cycle (2.7 ounces or 1/3 cup).
Appearance
Normal menstrual blood is dark or brownish, not bright red.
Normal menstrual blood does not clot easily because it:
- Is high in calcium
- Lacks the clotting factor called prothrombin
- Has very low levels of the clotter fibrinogen