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Natural family planning (NFP) is a form of contraception that involves recognizing the natural rhythms in a woman's fertility. Depending on their goals,
couples may choose to time sexual intercourse so that it falls
during the infertile phase (to avoid pregnancy) or the fertile phase (to achieve it). NFP is the sole method of contraception
permitted by the Catholic Church and has been given the derogatory
nickname "Vatican Roulette," a
reference to Russian roulette.
The calendar method, also known as the "rhythm method", relies solely on counting days in order to estimate the onset of a
woman's fertile period. There are also additional, more reliable forms of NFP, such as the basal body temperature method, the
cervical mucus method, and the symptothermal method. In addition, mothers of newborns can delay the return of their menstrual cycle (and thus, their fertility) by using the lactational
amenorrhea method (LAM).
As well as the religious imperative of many couples using the method, supporters typically advocate NFP because it is free
(apart from the purchase of a thermometer and charts), natural (introducing no chemicals into the body nor artificial devices to
modify the sex act), and the only family planning method that involves both the man and the woman equally (since the two must
communicate with each other in order to be aware of the woman's cycle and weigh their feelings about having children). For
detractors, however, the latter "benefit" is in fact regarded as a disadvantage.
NFP methods do require regular, consistent effort to determine when a couple's chance of fertility is low. For many women, the
times of high fertility coincide with the time of highest libido. The "scheduling" of sex required can be inconvenient for
partners who do not live together and are unwilling to abstain or use non-procreative forms of sex when they are able to spend
time together. For these reasons, other methods are more popular than NFP among large sections of society.
While the calendar method (by itself) is not the most reliable form of NFP, over a term of one year, some studies (by Planned Parenthood and, the US Food and Drug Administration) estimate that less
than 25% of women in sexual relationships who use the calendar method precisely will get pregnant, while others by NFP proponents
estimate the pregnancy rate at only about 9%. Even the pessimistic estimate is much lower than chance (85% of women not using any
contraceptive methods will become pregnant in one year), while even the optimistic one is considerably higher (that is, less
effective in preventing pregnancy) than optimally-used hormonal contraceptives (i.e. the pill). Numerous studies of couples in
North America and Europe using the sympto-thermal method of NFP have demonstrated 99% effectiveness at avoiding pregnancy.
In most women the menstrual cycle lasts between 24 and 32 days. It
starts with a menstrual bleeding. Ovulation takes place at some time between day 12 and day 18. Ova die if not fertilized within 24 hours of ovulation. Spermatozoa are able
to fertilize an ovum for a period of about three days after they have been ejaculated, although exceptional cases of
fertilization almost one week after intercourse have also been reported.
The period from the start of menstruation to ovulation lasts between 12 and 18 days, depending on the length of the cycle (24
to 32 days). Eliminating the seven days during which sperm can survive in a woman's body,
this leaves a first infertile period of five to eleven days from the beginning of menstruation. (Of course, during the first four
or five days of this period, the woman will be menstruating.) The second infertile period occurs after ovulation. The time of
ovulation can vary, especially if the cycle is not completely regular. Thus, if the couple wished to avoid conception, they must
abstain from intercourse for the first four days after the expected time of ovulation as well. Thus, the second infertile period
starts on day 16 after the beginning of menstruation in a woman with a 24-day cycle, and on day 22 in a woman with a 32-day
cycle. The woman can then be considered infertile until the next menstruation starts.
Observational Methods
NFP methods which not only keep track of the woman's menstrual cycle, but also make observations about the statue of a woman's
body, offer additional information for couples to use when considering having intercourse.
The basal body temperature method is based on the fact that two or three days after ovulation, hormonal
changes cause a rise in body temperature between 0.3 and 0.9C (0.5 and 1.6°F) that lasts at least until the next
menstruation.
The cervical mucus method (or Billings method, or Billings ovulation
method) involves checking the texture of the mucus secreted by the cervix. When a woman is not fertile, the mucus is
light or sticky. During the day before and the day of ovulation, (the most fertile time period), the increase in estrogen levels
causes more copious mucus that is clear and slippery.
The symptothermal method combines the techniques discussed above. Some women may also check the position and
feel of their cervix, and note breast tenderness or ovulatory pain (mittelschmerz), the lower abdominal pain or cramping
some women feel around the time of ovulation.
The saliva method involves examining saliva under a microscope for fern-like structures that indicate
ovulation.
The lactational amenorrhea method (LAM) of contraception makes use of the natural infertility which occurs
through breastfeeding. It is 99% effective during the first six months
postpartum in about 90% of women who:
- Breastfeed their infants exclusively
- Pacify their infants at the breast, not with pacifiers or bottles
- Breastfeed often
- Sleep with their infants
- Are not separated from their infants for more than three hours a day
- Take daily naps with their infants
Obviously, this method is only practical for women whose lifestyles allow for it.
See also: Pearl Index, Christian view of marriage
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