Each NFP method is focused on one or more signs of female fertility. They can be grouped into three categories
Cervical Mucus Methods (CMM)
The methods that observe cervical mucus are commonly called the "Ovulation Method" or "OM." In NFP education, a woman learns how to identify the normal, healthy, cervical mucus which indicates the days that sexual intercourse is most likely to result in pregnancy. A number of NFP providers teach a variety of approaches to the observation and charting of cervical mucus (e.g., Billings Ovulation Method Association—USA, Creighton Model FertilityCare™ Centers, Family of the Americas, etc.).
Sympto-Thermal Methods (STM) The methods that observe several signs of fertility and cross-check two or more of the signs to pinpoint ovulation are commonly called the "Sympto-Thermal Method" or "STM." STM typically combines charting of the Basal Body Temperature (BBT) and cervical mucus with other optional indicators, such as changes in the cervix and secondary fertility signs. A number of NFP providers teach a variety of approaches to the observation and charting of these signs (e.g., Couple to Couple League, Northwest Family Services, various diocesan programs, etc.).
Sympto-Hormonal Method (SHM)
The method that observes several signs of fertility and adds the use of an ovulation predictor kit (OPK) or fertility monitor is called the "Sympto-Hormonal Method" or "SHM." Similar to the STM, this approach adds the self-detection of reproductive hormones in the urine with the assistance of an OPK or fertility monitor. Various diocesan NFP programs make use of the SHM as well as Marquette University's Institute for NFP (Marquette Model).