Monday, September 10, 2007

Fact or Fiction: Full moon baby boom

Compulsive gamblers will tell you that to win a baby pool, always pick the date of the full moon closest to the actual due date. It's common knowledge that more babies are born on the full moon, right? Even nurses and doctors in labour and delivery will tell you that. So is there any truth to this ancient belief, or is it just a medical myth? A quick pubmed search reveals the answer: there is no correlation between lunar phase and birthrate. This evidence was been reported in 1979 in the New England Journal of Medicine, prior to that (1975) in the Canadian Medical Association Journal [pdf], and time and time and time again since.

There are two questions that immediately arise. The first is why is this belief still held, including by many well educated people, in the face of a large body of evidence to the contrary? (and supplementary to that, why are studies to that end still being done?) Obviously cultural reinforcement plays a large role - the myth continues to be repeated as fact. The second is where did the belief come from in the first place? Is it some leftover animal instinct where it was easier to deliver and/or protect newborns by the light of the full moon? Is it some cultural remnant from days when we worshipped celestial events like full moons and solar eclipses; some long, lost supersition? Is it simple recall or confirmation bias among mothers and hospital staff?

As for other common lunar beliefs, such as increased psychiatric disturbance or more full moon emergency room visits, again the literature doesn't support those beliefs (with the exception of a single study that showed clustering of seizures around the full moon). The Skeptic's Dictionary has a summary of full moon myths and some debunking. The bottom line is that the full moon has little effect on birth rates, hospital emergencies, stock market prices and (despite the root of the word) lunacy. Unless, of course, you're a werewolf.


11 comments:

Bayman said...

I do my best work during the full moon. Really. I swear.

Anonymous said...

I agree Bayman only does good work like once a month. :)

rob said...

But what about the major and minor fish feeding times previously mentioned on the bayblab.

Bayman said...

oooooooooooooooooooohhhh

ouch

dis from the anonymous coward

sadly i can't really argue.
once a month is very generous.
thank you.

Anonymous Coward said...

Hey that's not me, I'm not in a position to criticize your work, I'm on a two months vacation! Maybe it's one of the baybs?

Bayman said...

yes i know...i meant lower case ac not "the AC"...coward as an adjective rather than noun if you get my drift.

Colin, Canadian Nurse said...

As a health care professional, I agree with this theroy. Heres why. The human body conisit of 80% water. Durning the full moon, the tides in the ocean and lakes etc are affected in a large way. The moon pulls the tides further out and comes in at a higher level. Since the human body is 80% water, the body is also effected. For seniors with any form of dementia, they have an altered state of mind more so the usual. This will start usuall y 3 days before a full moon, will peak durning the night of the full moon, and will start to go back to their normal confusion level 3 days after the full moon. As for the theory of increase ER visits this is true, for the same reasons. Some illness are greatly influence by the moon and symptons can increase as well. Physc patients as can become more, depressed, pyschotic, and form alter behavior durning this time. While CMJA, NEJM may state that there is no correaltion between full moon and medical issues, take the word from a nurse who actually see's the effects of it. We dread a full moon at the hospital everytime it comes around!!!

kamel said...

Colin, you should check out the last link of the post (Skeptic's Dictionary). Around the middle of that page ('misconceptions') it discusses exactly the same things you're talking about.

But just to clarify a misconception about tides: a higher tide (spring tide) is higher because the sun, moon and earth are all in a line so the pull of the sun is added to the pull of the moon. The tides are just as high during a new moon (again, because the earth and moon are all in a line). According to your theory, ER visits, dementia and other altered behaviour should also peak around the new moon. Is that the case?

Anonymous said...

I like to see anything on this topic! I was a full moon baby and both of my daughters born came on full moons with my water breaking to get things rolling. I am due in September and we will see what happens with this one!

www.orense-3d.com said...

Really useful information, thanks so much for the article.

Anonymous said...

Wow, not to put more stock in this, but funnily enough all 3 of my kids and myself were born between 1 and 3 days of a full moon. Only my wife was a little further at 5 days (still pretty close, but that's a 10-day (+/- 5 days) range which is less impressive).

Pretty amazing that out of 5 of us no-one was born anywhere close to +/- 15 days of a full moon.

However, not one of us was born precisely on the full moon, so any baby pool would have been lost ;)