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Scientists Describe Internal Clocks That Don't Follow Day and Night Cycles
sciencehabit writes "Almost all organisms, from bacteria to mammals, have a circadian clock—a mechanism in their cells which keeps them in sync with Earth's day-and-night cycle. But many organisms follow other rhythms as well. Now, new research provides the first evidence that animals have molecular cycles independent of the circadian rhythm. They include a sea louse whose swimming patterns sync up with the tides, and a marine worm that matures and spawns in concert with the phases of the moon. The discoveries suggest that noncircadian clocks might be common and could explain a variety of biological rhythms."
I think that the female cycle is close to the lunar cycle, but not exactly synchronized with it. It would be similar to people having a 22 hour day cycle instead of 24.
The menstrual cycle can be anywhere from 25-35 days, with an average of 28 days.
The lunar cycle is 29.5 days.
On a sidenote, imagine the horror if all women of the world would have their period exactly synchronized!
http://en.wikipedia.org/wiki/Menstrual_cycle
http://en.wikipedia.org/wiki/Lunar_phase#Overview