The effectiveness of the CrMS has been extensively studied. The method effectiveness (perfect use of the system) is 99.8%. The use-effectiveness (the actual use of the couple), because some couples do not use the system exactly as designed, is 96.8%. Compared to contraceptive use with the typical use-effectiveness ranging from 70-95%.
For couples trying to achieve pregnancy, by selecting the days of fertility for intercourse,
the pregnancy rate for the first cycle trying to conceive in couples of normal fertility is 76%, 90% by the second cycle, and 98% by the third cycle. In couples with infertility and subfertility, the pregnancy rate using just the CrMS without the use of NaProTechnology is 20-40%. Using the system along with NaProTechnology the pregnancy rate is up to 80%. 1-3 times more successful than IVF.