A method of "family planning" developed by Doctors John and Evelyn Billings. Essentially, a women or couple learns to identify the various physical signs (mainly mucus production at the cervix) of fertility so she (they) can avoid having intercourse (or at least unprotected intercourse) if she doesn't (they don't) want to have a child, or can have more intercourse then if she does (they do). Mucus production can either be observed directly through an examination, or recognized through the sensation it causes at the vulva.
As birth control, it’s usually considered a "natural" alternative to "artificial" contraceptives, and is thus favored by people who wish to avoid "artificial" contraceptives (either because they don’t like them, they prefer natural methods, or because they’re afraid God will send them to hell if they use 'em). The ovulation method is more reliable then most other non-artificial contraceptive forms of birth control (such as the rhythm method). Other benefits are that it’s essentially free and unlikely to cause unwanted side effects (except for pregnancy if it doesn’t work). It will allow a woman to have intercourse without risk of fertilization about two thirds of the time.
The main disadvantage of the ovulation method as a form of birth control is it’s somewhat finicky (there are charts you have to fill in and interpret), requires careful observation skills (which some people lack these skills), and might offend the squeamish (some people are uncomfortable paying that careful of attention to their bodily secretions). Its main disadvantage as a method of achieving pregnancy is that it’s not as much fun (unless you like charts a lot) as simply having sex on a daily basis.
Personally, I have a few problems with The Billings Ovulation Method: First, they claim that "Scientific studies indicate that with proper instruction and motivation, this method in actual practice is 99% effective". I cannot help but wonder how many failures they had to classify as having improper instruction or motivation in order to reach this figure.
Second, even 99% effective is not that great. If everyone used only this method there would still be too many unwanted pregnancies. If you really want to have sex and don’t want to have children you need to combine methods of contraception, which does not seem to be encouraged under the Billings Method.
Third, they assert several times throughout their literature that the fertility of a couple depends on an "harmonious relationship between husband and wife". This is very likely true (though I wouldn't mind some evidence to back it up), but is troublesome in a document about birth control, "Don’t worry, honey, we’ve been fighting so there’s no chance we’ll conceive." In their defense, they wish to help couples who want pregnancy as much as those who don't, but I still don't like it.
This info was mainly taken from their website. People seeking more information should try there, at:
http://www.billings-centre.ab.ca
This has been a nodeshell rescue.