Natural Family Planning methods (NFP) are variations of the rhythm method. This covers techniques used to determine a woman’s fertile and infertile periods within her menstrual cycles.
This is done by knowing when ovulation (the release of an egg from one of the woman’s ovaries each month) takes place and abstaining from intercourse during a woman’s fertile days. Fertility is known by checking the calendar and observing certain bodily signs like fluctuations in body temperature or changes in the vaginal mucus.
“Each of the approaches in natural family planning involves a conscientious awareness of when you can become pregnant, which is but a brief span approximately in the middle of each menstrual cycle – from about 72 hours before ovulation to about 24 hours after ovulation. The key is to determine when these days are and then to avoid having intercourse during that time,” said Dr. David E. Larson, editor-in-chief of the “Mayo Clinic Family Health Book.”
“All told, a couple needs to abstain from intercourse seven to 10 days a month in order to have the greatest chance of preventing pregnancy,” added the editors of Consumer Guide’s “Family Health & Medical Guide.”
NFP is the only birth control method approved by the Catholic Church but millions of people throughout the world rely on it either because of religious convictions, poverty (which prevents them from buying other effective contraceptives) or ignorance of other contraceptive methods.
There are four types of NFP methods: the temperature method, the calendar method, the mucus inspection method and the muco-thermal method. Each of these techniques has a different way of determining the time of ovulation.
How good are these methods? NFP has a success rate of 80 to 99 percent depending on the kind of technique you use. In general, the more restrictive the method, the greater the chances of avoiding pregnancy.
“This may surprise you: if followed faithfully, some types of ‘natural’ birth control can prevent pregnancy better than the diaphragm or condom. But there’s a big hitch: the most effective versions of this method are so restrictive that it’s all too easy to slip up,” according to Deborah Franklin in Health magazine.
In the temperature method, ovulation is determined by taking the woman’s temperature daily first thing in the morning after waking. This should be done preferably at the same time each day using a sensitive “basal” thermometer. It’s also advisable to take the temperature at the same spot – either in the mouth or armpits. A slight rise in body temperature usually indicates ovulation. Sex should be avoided for at least two days after the temperature increase.
“Near the middle of the menstrual cycle, the temperature may drop slightly (indicating that ovulation is about to occur) and then rise rapidly and continue to climb for the next three days. The temperature will not return to preovulation levels until the beginning of the menstrual period. The ‘safe’ days to have sexual intercourse are from four days after the sudden rise in temperature until three or four days after the end of the period. It is important to become familiar with the menstrual cycle by recording temperature levels for several months before relying on this method of birth control,” said the editors of Consumer Guide’s “Family Health & Medical Guide.”
The calendar method works by determining the probable day of ovulation with the help of a doctor. To do this, a woman must keep a record of her menstrual cycle for a year or more. From this record, the doctor can pinpoint “safe” and “unsafe” days.
“Subtract 18 days from the number of days in the shortest cycle (14 days from ovulation to your period and four days for the average life of sperm) and 10 days from the longest cycle (14 days from ovulation to your period, minus one day for the lifespan of an egg and minus three days for a margin of error) . The numbers you calculate are the first and last days of your cycle during which you can become pregnant,” Larson explained. (Next: The Billings birth control method.)