Creighton Model FertilityCare System

The Creighton Model FertilityCare System (Creighton Model, FertilityCare, CrMS) is a form of natural family planning which involves identifying the fertile period during a woman's menstrual cycle. The Creighton Model was developed by Thomas Hilgers, the founder and director of the Pope Paul VI Institute. This model, like the Billings ovulation method, is based on observations of cervical mucus to track fertility. Creighton can be used for both avoiding pregnancy and achieving pregnancy.

Conceptual basis
Hilgers describes the Creighton Model as being based on "a standardized modification of the Billings ovulation method (BOM)", which was developed by John and Evelyn Billings in the 1960s. The Billingses issued a paper refuting the claim that the CrMS represents a standardization of the BOM. According to the Billingses said that those concepts are two different methods and should not be seen as interchangeable.

Effectiveness
For avoiding pregnancy, the perfect-use failure rate of Creighton was 0.5%, which means that for each year that 1,000 couples using this method perfectly, that there are 5 unintended pregnancies. The typical-use failure rate, representing the fraction of couples using this method that actually had an unintended pregnancy, is reported as 3.2%.

For achieving pregnancy, no large clinical trials have been performed comparing ART and NaProTechnology. Only observational one-arm studies have been published so far. In the larger of these three studies, 75% of couples trying to conceive received additional hormonal stimulation such as clomiphene.