“Lunaception” is a term coined by author Louise Lacey in her 1974 book of the same name. Lacey (who freely admits she has NO scientific evidence to support the idea and that it is entirely based on “native wisdom” and anecdote) believes that the moon is capable of altering fertile patterns.
The theory is based on anthropological studies of various cultures that believed that menstruation was somehow tied to the moon. In fact, in many languages, the words for moon and menstruation are even based on common root words – in English, the word menstruation comes from the Latin word “mensis” meaning month, and the word “moon” also seems to stem from that same word (although the Latin word for moon is “luna” so the connection is hardly as straightforward as Lacey would have us think.)
The premise underlying Lunaception is actually quite intriguing. Prior to the invention of electricity, or even the discovery of fire (our ancestors lived for hundreds of millions of years sleeping outdoors without fire), our fertility evolved cyclically, governed by the natural rhythms of the earth, and some of these evolutionary anomalies are still alive and well within us. Much like a tailbone probably once supported tails we no longer grow, our bodies may have latent vestigial biorhythms that we aren’t even aware of.
Lacey purports that most women experiences their menstrual cycles with the phases of the moon and at more or less the same time as other women. The idea of menstrual synchrony has been around since the early 70’s – a couple of fairly decent studies seem to support the idea that women who live in close quarters with each other, start to ovulate and menstruate on or near to the same schedule. So whether or not the moon has anything to do with it, our tribal ancestors may very well have been all on the rag at the same time.
The conclusion is, that since we evolved sleeping under moon for hundreds of millions of years in close quarters with our fellow female primates, SOMETHING, whether it is gravity, light, or the elusive ion, affects our bodies in such a way that it can enhance or limit our fertility.
Clearly, the gravity of the moon does affect the oceans, so the idea that the moon may have some sort of similar affect on the fluids of the human body makes sense on a gut level. However, the moon’s gravitation is not the same around the world (there are no tides at the equator and that’s probably where most of our evolutionary past was spent) and high tides occur BOTH when the moon is full and when the moon is new. This is because the highest tides occur when the moon and sun are in alignment and have nothing actually to do with the phases of the moon…when we see a crescent moon for example, the rest of the moon is STILL THERE, we just can’t see it. (for a good explanation, see http://home.hiwaay.net/~krcool/Astro/moon/moontides/) So whatever force may underlie lunaception, gravity has nothing to do with it.
Much more likely is that light emanating from the moon somehow affects our body chemistry in such a way as to enhance fertility. Solid science exists to show that day length and artificial light can affect health and fertility. The pineal gland, a little part of the brain referred to as “the third eye”, produces melatonin and seems to be affected by light. Interestingly, the ovaries of rats who had their pineal glands removed, grew larger in size, and the ovaries of rats raised in constant bright light were unusually small. Children who have tumors of the pineal gland go into puberty very early. The pineal gland and light apparently DO affect fertility. Why might such a thing have evolved? I don’t know what the “official” explanation might be, but to me it seems like ovulating in the full moon makes a heck of a lot of sense, if only so you could see what you’re doing!
And what about the idea that this is some leftover instinct caused by menstrual synchrony? Well, it turns out that menstrual synchrony may not even be real. http://www.straightdope.com/columns/read/2429/does-menstrual-synchrony-really-existNow, I worked in a dog kennel for 2 years and I did notice that female dogs (yes I know that’s not the right terminology but this is a family website LOL) kept in the same pen did seem to cycle together, but it was very far from 100% of the time. So I have to put this into the plausible category as well, but not proven.