Not trying to get into a discussion of logic, by definition use of a diaphragm or just spermicide violates the intent of natural family planning. Use the diaphragm, you are no longer using NFP. That is not to be critical, simply to help you clarify your intent.
You know from other posts over the years that I am not an advocate of natural planning for young women in dating relationships. For someone more mature and in a stable relationship, the mucous examination can be helpful. Simply using the calendar is very restrictive and if the woman is among those who ovulate twice or more in many months, it simply does not work.
For a woman who wishes to use NFP "most" of the time, she would use her basal temperature and mucous indicator to determine when the diaphragm is to be used. This includes the effort to measure plot your menstrual cycle AND the effort to use the diaphragm. If your cycle gets confused by illness or diet or whatever, pregnancy is still possible.
Recognizing that you are avoiding hormones, compare the effectiveness of spermicides (jelly, film, foam, suppository) with the effectiveness of the diaphragm (which must be used with jelly). Of 100 sexually active women properly using the diaphragm for a year, it is likely that twelve to fifteen will become pregnant; vaginal spermicides alone, 15-17 become pregnant.
Certainly you can combine anything, other than hormones, with NFP. Why not use the diaphragm all the time and be a bit safer. Or consider an IUD.
Posted: 30 Sep 03:03