As a RC theologian, I am aware that the Catholic Church tends to be so promotional of NFP as to neglect to inform users that, like anything else, there is also a down side. This practice is unfortunate. It destroys confidence and subverts “honesty in advertising.”
Consider, for example, the medical advice given to patients by The American College of Obstetricians and Gynecologists:
How effective is it in preventing pregnancy?
Natural family planning is not as effective as most other methods of birth control. One in four women who use this method become pregnant. The method is not suited for the following women:
• Women who should not get pregnant because of medical reasons
• Women with irregular menstrual periods who may not be able to tell when they are fertile
• Women with abnormal bleeding, vaginitis, or cervicitis (these make the cervical mucus method unreliable)
• Women who use certain medications (for instance, antibiotics, thyroid medications, and antihistamines) that may change the nature of vaginal secretions, making mucus signs impossible to read
• Women with certain problems unrelated to fertility (for instance, fever) that can cause changes in basal body temperature
If the bishops would include these warning with their NFP promotional pitches, then Catholic women who suffered through unwanted pregnancies would feel relieved that it was not their fault that they got pregnant when using NFP. Meanwhile, those considering using NFP for the first time would be encouraged to know that the bishops are straight shooters that are not blinded by ideological and theological factors.
Prof. Aaron Milavec