More info on the Couple-to-Couple League's form of the Sympto-Thermal Method can be found here.
Natural Family Planning is the concept of using the woman's body's signals to space children without the interference of artificial birth control methods such as the birth control pill, IUDs, depo-provera (the shot), condoms, sponges, et cetera. The method I use is called the Sympto-thermal method and takes into account the body's rhythm, mucus discharge, temperature, and cervix positioning. I am using the Couple-to-couple league's workbook and aid. The cost for the workbook, supplies, and the included year's membership (with free consultation) is $120. D and I decided to order the home study course and intend to attend the classes in person as soon as possible (included in the membership cost).

My personal reaction to this news was complex. I felt ignorant, guilty, sorrowful, and humbled. In my arrogance, I had believed that I could make a decision which directly countered a basic principle of my faith (Roman Catholic) based on very minimal research or understanding of the actual functions of birth control. In doing so, I had altered my body chemistry and quite possibly caused the miscarriage I had experienced a year prior.
While its reckless approach to life was the biggest reason for my turn from hormonal birth control (HBC), understanding the functions of HBC helped me to realize unadvertised negative side effects. When your body releases an egg from its follicle, the empty follicle (called corpus leteum), then begins to produce progesterone. Progesterone causes the pituitary gland to suppress ovulation. Psychiatric effects of progesterone include depression, mood swings, emotional instability, aggression, abnormal crying, insomnia, forgetfulness, sleep disorders. Sound familiar? Progesterone is basically the PMS hormone. Not surprisingly, progesterone levels remain high pretty much throughout pregnancy.
HBC works by combining varying levels of estrogen and progestin (a synthetic form of progesterone). Essentially, HBC constantly increases the amount of progesterone in your system, telling your body that you are pregnant 3 weeks out of each month. The week of "pink [placebo] pills" is included to allow withdrawal bleeding (basically, it flushes your system). So in other words, on HBC, you're either constantly PMS-ing (hormonally speaking) or else you are on your period.
Although these alone are substantial arguments in favor of NFP, there are a number of other benefits to using a more natural approach to birth spacing.
It is well-known that nearly half of all marriages in the US end in divorce. According to enrichment journal on the divorce rate in America:
The divorce rate in America for first marriage is 41%
The divorce rate in America for second marriage is 60%
The divorce rate in America for third marriage is 73%
So it's incredibly heartening to look at the divorce rates for NFP-practicing couples. According to a study by the Family of the Americas Foundation, divorce rates in NFP-practicing couples is only 0.2%! "Jottings" by John Kipley of the Couple-to-couple league, cites multiple informal studies placing the divorce rates of NFP-practicing couples between 1 and 5 %.
Natural Family Planning works by educating a couple about how fertility works. What signs indicate increased fertility, when to expect ovulation, and when to expect menstruation. Without artificially controlling these things. This can be a boon not only in understanding one's body, but also in the future should the couple ever desire to conceive again.
One of my concerns when approaching the Natural Family Planning debate was effectiveness. However, this chart describes the effectiveness rate of different pregnancy prevention methods.
No birth control method 20%
Calendar Rythm (Ognio-Knaus) 87%
Withdrawl 91%
Ovulation (or Billings) method 96%
Diaphragm with spermicide 97%
Foam 97%
LAM (Breastfeeding) (first 6 months) 98%
Condom 99%
IUD 99%
Pill 99.7%
Sympto-Thermal Method 99.8%
Tubal Ligation 99.6%
Vasectomy 99.85%
Castration, removal of ovaries, abstinenct: 100%
This data was reported by the U.S. Department of Health, Education and Welfare, and various respected medical journals.
Artificial forms of birth control intentionally separate the act of sex from the act of creation. Therefore, when a couple practicing artificial forms of birth control gets pregnant as a result of "protected" sex, the resultant life is seen as burdensome, rather than as a blessing. The child is a surprise, and it is easy to see that life as an unwelcomed surprise. Practicing NFP, however, serves to constantly remind the couple that the act of sex is, in fact, a life-giving act. As such, an unexpected pregnancy can still be a welcomed surprise, because after all, sex causes babies.