NFP is not a single method. Rather, it is a group of different “methods for planning and preventing pregnancies by observation of the naturally occurring signs and symptoms of the fertile and infertile phases of the menstrual cycle, with the avoidance of intercourse during the fertile phase if pregnancy is to be avoided.” (World Health Organization, 1982)
When barrier methods (condoms, diaphragms, etc.) are used at the fertile time instead of abstinence from genital contact, then these methods are called â€œfertility awareness combined methodsâ€? (FACM).
Effective for avoiding pregnancy
Can be used to conceive
No side effects
High user satisfaction and continuation rates (70-90%)
Increased couple communication and intimacy
Insight into normal and abnormal functioning of the womanâ€™s reproductive system
Abstinence is required for 9 or more consecutive days mid-cycle (depending on the method and the womenâ€™s cycles). Studies suggest that couples using NFP have intercourse about as often as most couples using other methods (5-6 times per month), but more concentrated into the infertile days.
FAC methods do not require abstinence, just use of barriers on fertile days, but have somewhat higher pregnancy rates than pure NFP methods.
NFP provides no protection against sexually transmitted infection.
NFP is based on the fact that there are about 6 days of a womenâ€™s menstrual cycle (perhaps more properly called the reproductive cycle) when insemination can result in pregnancy (the 5 days before ovulation and the day of ovulation itself). There is some imprecision in identifying these 6 days, which is why 9 (or sometimes more) days of fertility are usually identified by an NFP method. The most effective symptom for identifying the approach of ovulation is the change in a womenâ€™s vaginal discharge that results from a change in the fluid produced by the cervix, or opening of the womb. The cervical fluid (cervical mucus) changes in its chemical and physical properties in order to allow for sperm survival for up to 5 days until ovulation occurs. The woman observes a discharge that is progressively more stretchy, slippery, and clear. Then it abruptly reduces after ovulation. Basal body temperature also rises after ovulation. Calendar calculations have also been used to define the fertile days of the menstrual cycle and are still sometimes used, but they are less accurate. Reproductive hormones can also be measured in urine, but this is generally no more accurate than the careful observation of vaginal discharge. Some women say that they find it helpful to identify their fertile days by feeling their own cervix with their fingers, but this is not generally necessary and the systematic medical evidence for feeling the cervix is weak. Saliva monitors have shown to be NOT reliable. Ovulation pain (mittelschmerz) does occur in many women, but it can occur before, during, or after ovulation.
Pregnancy rates are reported as percentages during one year of perfect use or typical use. Perfect use means use exactly as directed. Typical use means what couples actually do, including errors and changes of intention. I will talk here just about effectiveness to avoid pregnancy. Effectiveness to conceive is another topic. Most pregnancies that occur during NFP use result from sexual intercourse at a time that a couple knows to be fertile, according to the NFP method. There are few true surprise pregnancies with NFP. Typical use pregnancy rates vary very widely between studies, because the characteristics and motivations of the population vary widely. Quality and amount of instruction in NFP also impacts pregnancy rates for NFP users. To maximize effectiveness usually requires personal instruction from an experienced teacher.