I'm glad to see another NFP supporter here!
"NFP is Birth Control..."
Though the Sympto-thermal, Creighton, and Billings methods of Natural Family Planning are all more effective than any form of artificial contraception, in preventing pregnancy in any given month, I wouldn't refer to them as "birth control," for one who is using NFP is not trying to "control" anything external to himself or herself. The couple using NFP does not believe it is within their power to control the miracles of conception and birth; what they do believe, and know, is that they are able to control their actions, with an eye to the consequences that follow.
Billings Ovulatory Method, over 99.5% accurate: www.woomb.org
Sympto-Thermal Method, over 99.3% accurate: www.ccli.org
Creighton Model, nearly 100% accurate: www.creightonmodel.com, www.popepaulvi.com