Fertility awareness

To use natural family planning, (NFP) a couple voluntarily either avoids sexual intercourse during the fertile phase of the woman's cycle (time when the woman can become pregnant) or has intercourse during the fertile phase to achieve pregnancy. There are four types of NFP: the calendar ("rhythm") method, the basal body temperature method, the cervical mucus method, and the symptothermal method. Mothers of newborns can also use the natural lactational amenorrhea method (LAM) of contraception.

The calendar method (or "rhythm method") of family planning is a means of controlling conception by timing procreative sex to coincide with or avoid the times during which the woman expected to be fertile. It can be used to increase the likelihood of pregnancy or to avoid it.

If the calendar method is being used for contraception, sexual intercourse is timed to avoid the fertile period. However, this leaves only a short "safe" period of infertility, and this method is completely unreliable for women who do not have a regular cycle, who are not willing (or able) to calculate their fertile periods, or who cannot abstain from sex when they choose. The method itself is 91% effective when used perfectly. Perfect use, however, is a challenge, making the riddle "What is the technical term for a woman using the rhythm method? -- A mother!" a tiresome cliché.

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.

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) 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 all of the techniques discussed. Some women 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 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 the majority 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 practical for only a limited number of women.

NFP is the sole method of contraception permitted by the Catholic Church, thus some have dubbed it "Vatican Roulette." The term is ironic in that NFP as described is very effective, but women who do not (or cannot) use it rigorously experience a high "failure" rate.