I know you're all super excited that this week is here! Not to worry, I won't be writing a novel about why we chose to use Natural Family Planning (since I already did so in a series here: intro, part 1, part 2, part 3a, part 3b). Instead, I just thought I'd write short pieces debunking different myths about NFP and contraception. Keep checking all week - there will be cute little videos!
First misunderstanding to correct: NFP is not the same as the Rhythm Method. According to the Couple to Couple League International (a go-to site about NFP):
Calendar Rhythm basically assumed that women would have 28-day cycles with ovulation around Day 14. It was ineffective if cycles were either shorter or longer. Modern NFP acknowledges that a woman can routinely have cycles that are shorter or longer than the “average” of 28 days, and that her cycle can even vary from month to month. NFP users make their interpretation choices based on the fertility symptoms they are currently experiencing this month, which is why it is still highly effective for women with irregular cycles, unlike Rhythm. (http://ccli.org/nfp/basics/faq.php)
Unfortunately, most doctors do not realize this, because they are usually not taught about natural methods of family planning in MD/DO school. They, along with most other secular sources, frequently conflate NFP and Rhythm.
That brings us to a second important correction: NFP is actually super effective! It's as effective as contraception, and in fact more effective than many specific types of contraception (condoms, for example). Some sources dispute this, but that is because they are including statistics about the Rhythm Method, which NFP users already acknowledge to be less effective. When looking at research on NFP, it's important to see that "sympto-thermal methods" are what are being gauged, instead of "calendar methods."
NFP is 99% effective. For more details about this, check out this interesting and informative article about the effectiveness of Natural Family Planning, with thorough explanations about how effectiveness is measured, among other things: http://ccli.org/nfp/basics/effectiveness-p01.php.