What determines heaviness of menstrual flow?

My menstrual flow is always pretty heavy, but every once in a while, I’ll have a horrendous period, with cramps the usual 600 mg of ibuprofen barely touches and drenching flow with huge clots.

What is the physiology/endocrinolgoy beind these abnormaly heavy periods?

I just wanted to see if someone will answer this, so I am giving this a friendly nudge towards the top. My wife actually bought this up last week. Her period usually comes like clockwork, with steady flow the first two days and minor ‘spotting’ the last two days. Her most recent period was actually very heavy, to quote freckafree, a drenching flow with huge clots.

Hopefully someone with some sort of knowledge will help me understand my wife’s body a little better.

Women’s bodies vary a lot. Average menstrual volume for all women is anywhere from 1/4 cup to 1 cup per cycle, although most women don’t vary from period to period a whole lot. Cites in this post.

If a period is late and then very heavy, with lots of clots, then there’s a good chance there was a very early miscarriage before the woman even knew she was pregnant. It’s estimated that 50% of fertilized eggs are lost before a pregnancy is detected. (cite in this post) and most of those are lost in “heavy periods”.

Other than that, I don’t know of a Western Medicine explanation for the anomalous heavy period in a normally regular woman*. I know of several explanations within the paradigm of Traditional Chinese Medicine, but they’re not easily explainable to the layperson, and will just get shredded as pseudoscience on this board anyway, so I’m not going to waste my time going there. You’ll just have to take my word for it that millions of people around the world know exactly why it happens and what to do about it, but Dopers won’t accept it as a valid medical system because it contains words like “constrained qi” and “accumulation of damp”.

*That’s not to say there isn’t one.