The rhythm method is one of the first fertility awareness methods to be widely practiced. It is one of the oldest methods of natural birth control and by far one of the best-known forms of fertility awareness. Unfortunately, it is not necessarily the most reliable method of preventing a pregnancy.
Theory and Practice
The rhythm method is based on three ideas. Firstly, that women ovulate 14 days before menstruation begins, give or take two days. Secondly, that sperm can survive inside a woman for three days. And lastly, that an egg can only be fertilized within 24 hours of being released from the ovaries.
Based on these assumptions, the rhythm method requires a woman to count back 14 days from the first day of her period. This will presumably be the day on which she ovulated and will ovulate the following month. In order to avoid pregnancy, she will need to abstain from sex or use another form of birth control, like condoms, around this time.
While this method is fairly simple to follow, it is not necessarily applicable to all women. The first problem lies in the assumption that ovulation will always occur at the same time every month. While it would make life a lot easier for women if this were true, the reality is that the majority of women ovulate at a different time every month. Although they may follow a similar pattern, no woman has a menstrual cycle that is identical every month.
Another issue with the rhythm method is the belief that sperm are only viable inside a woman for up to three days. It has been found that sperm may be able to survive for as much as seven days inside a woman. Therefore, it would be necessary to avoid having sex for at least a week prior to when a woman believes ovulation will occur.
Moreover, this type of contraception offers absolutely no protection against sexually transmitted diseases. Therefore, it will still be necessary to use a condom if you think you may be at risk of an STD.
The rhythm method has an average failure rate of 13 to 20%. It is not recommended for women who have irregular cycles or who do not have menstrual cycles that are exactly the same number of days every month.