Natural Family Planning is a method for understanding the female reproductive cycle well enough to plan the optimum timing for trying to conceive or avoiding pregnancy. It is a system by which a woman can get to understand her own body's signs well enough to determine that her cycles are normal and healthy. Natural Family Planning is not the "rhythm method."
Natural Family Planning utilizes the methods of taking and charting the basal body temperature, and noting changes in cervical fluid during the month in order to accurately determine ovulation, and the best possible timing for achieving or avoiding pregnancy. It is also an accurate method for determining whether one is pregnant even before the over the counter tests show results.
Basal body temperature is the body's temperature upon waking in the morning. If taken consistently, at the same time each day, and before getting out of bed, patterns can be noted which indicate that ovulation has occurred. A digital basal thermometer is the most accurate for taking the basal temperature. From menstruation until ovulation, the basal body temperature will stay within a certain low range, usually between 97.3 F and 97.7 F.
It may vary for some women, but will usually stay within a small range. Once ovulation has occurred, there is a thermal shift to the upper range of 97.8-98.5 or so. This is called the luteal phase. The luteal phase lasts for 10-12 days in each cycle. A fertilized egg needs 6-8 days to travel down the fallopian tube and implant in the waiting uterus. If it is not fertilized, it disintegrates and is flushed out with the menstrual lining. If the luteal phase is too short, pregnancy cannot occur. Natural Family Planning can help cue a woman in to whether her cycle is normal and healthy.
The basal temperature will drop back down again when menstruation will occur. If temps stay in the upper range, the likelihood of pregnancy grows with each day past 10-12 days past ovulation. If there are 18 consecutive days with high temps, pregnancy is likely.
For couples trying to achieve pregnancy using natural family planning, the prime time for intercourse is the 24-48 hours before ovulation. Since basal temperatures indicate that ovulation has occurred, other signs must be noted to predict ovulation is eminent.
Cervical fluid changes throughout the cycle. It goes through a cycle of dry-creamy-lotion-like, and finally similar to egg-white as ovulation approaches. A woman who is tuned-in to these signals can plan her and her partner's timing to either avoid or plan the best chances for achieving pregnancy.
Books and websites for Natural Family Planning are widely available. An excellent resource is called "Take Charge of Your Fertility." Natural Family Planning is more than a method for avoiding or achieving pregnancy. It is a way for women to learn to understand their bodies in profound ways. It also gives a woman valuable information about her normal cycles, and when things are not normal. It could help a woman provide her obgyn with important information.