Natural family planning is based on calculating when ovulation (release of an egg from one of the woman's ovaries each month) occurs. The couple then abstains from intercourse during the fertile period.
A man's sperm can live in a woman's body for about two days. The egg can live for about 24 hours after ovulation. A few days are added to this fertile period for safety's sake, because it is so difficult to determine just when ovulation occurs. All told, a couple needs to abstain from intercourse seven to ten days a month in order to have the greatest chance of preventing pregnancy.
There are three methods a woman can use to determine when she ovulates. The temperature method is one of the most reliable. Each morning on awakening and before getting out of bed, she takes her temperature with a special basal temperature thermometer (which measures temperatures only between 96°F and 100°F) and records it on graph paper.
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 the temperature levels for several months before relying on this method of birth control.
The mucus method may also help determine the time of ovulation. Each morning the mucus from the vagina and cervix is examined. Cervical mucus undergoes changes as hormone levels vary during the course of the cycle. To detect these changes, the vaginal area is blotted each morning with a facial tissue, and then the mucus is tested between the thumb and forefinger. After the menstrual period, there will be several days with no mucous discharge. This is followed by several days of a thick, sticky yellow or white discharge. There will then be one or two days when the mucus becomes transparent and very slippery, with the consistency of raw egg whites. The mucus will form a string between the thumb and forefinger. This is when ovulation occurs. After ovulation, the mucus again becomes thick and sticky, or there may be no mucus at all.
The fertile period begins with the thick, sticky yellow or white discharge and continues until about three days after the phase when the mucus has the consistency of egg whites. Intercourse should be avoided during this time. In other words, the safe period is from three days after the slippery mucus stage to about three days after the end of the menstrual period. The use of certain medications (such as antihistamines), which alter mucus production throughout the body, will make determination of ovulation by the mucus method difficult, however.
The calendar method is also an option for women. A record of menstrual cycles is kept for one year or more. The doctor will then use the record to figure out the most likely day of ovulation, based on the fact that the average woman menstruates 14 days after she ovulates. However, any individual woman may vary from that average, so the calendar method is not a precise system.
Natural family planning does not require the use of mechanical aids or drugs. The effectiveness rate for this kind of birth control is currently up to about 80 percent, depending on the care with which the techniques are followed. However, even in women with regular cycles, fluctuating factors such as illness, fatigue, stress, and use of certain drugs can delay ovulation or cause the techniques used to determine ovulation to be inaccurate, thereby throwing off the most careful calculations.
We have now covered the many common methods of brith control. You should consult your doctor for more specifics relating to your own case.
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