Methods of family planning that are based on 'fertility awareness' try to identify the fertile days of a woman's menstrual cycle. Names used to describe this approach to birth control include 'rhythm,' 'natural family planning' and 'periodic abstinence.' The goal is to avoid sex on the days when the women might get pregnant. Couples could also use these methods with a condom or they could use withdrawal.
In February 2012, we did computer searches for randomized trials that examined family planning methods based on fertility awareness. For the original review, we also looked at studies mentioned in these trials as well as in review articles. We included trials that compared a fertility awareness-based method with a placebo ('dummy') or with another method including a different fertility awareness method. The test method could also be compared to a fertility awareness-based method used with another type of birth control.
Three studies were found; one was from Colombia and two were from Los Angeles, California. Due to weak methods, we could not analyze any data. Pregnancy rates could not be determined. The Colombia trial found similar numbers of women became pregnant in the ovulation and symptothermal groups. The Los Angeles trial observed more pregnancies in the group with the ovulation method. The USA trials found it hard to recruit couples, while the Colombia report did not mentioned that issue. Drop-out rates were high. In the two larger trials, most participants stopped their method early.
We still do not know how well these methods work for family planning. Even with a lot of training and support, most people in these trials stopped early. Birth control methods should be tested carefully before they are widely shared and used. Randomized trials are the best test of whether something works or not.