Not a captive, I'd be interested in hearing what you find out about contraception. At Church this past Sunday, our priest mentioned again that, although artificial contraception is a serious sin, 80% of American Catholics use it anyway. The rules haven't changed but the conduct of the people in the pews has conformed more closely to the values of the society in which they live.
I don't know about the Rhythm Method but today people use NFP, Natural Family Planning. It is an abstinence during fertility based approach. However, it is to be prayerfully reconsidered month to month and is only to be used in serious situations. Almost anyone who uses it continuously for birth control is considered to be abusing it and living in mortal sin.
For instance, I had one friend who used NFP for about six months because she was having some serious health problems and taking medicine that could have killed a fetus. I now another woman who uses it pretty much constantly because she's a severed diabetic. In her last pregnancy, she went into a coma for four months, the baby was born with severe defects and died at 10 months old. Any future pregnancies would kill her, as they've been progressively more dangerous.
Regardless, that's not what this post is about. Don't mean to hijack. I'll shut up.
StAnn