The Church has already lost this argument! There are very few Catholics who look on contraception as a sin, but rather as a tool, given to the world by a loving God, to help rationalise married life and the care and love of children.
Gone are the days when each family consisted of six, ten or sometimes double that number of children, bringing their families into a life of poverty and neglect of the individual child.
God has blessed us with a growing knowledge of medicine and how it can be used to help us live good and healthy lives. How can a bunch of elderly, celibate men, with no experience at all of married life, decide how married couples should behave in the bedroom?
The Church has always got itself hung up above sex and made it the major sin of choice! Is this because it is ongoing, whereas murder is usually a one-off? Where is their logic?! Artificial contraception does not harm other people which must be one of the most important criterion in regard to the severity of any sin. Consenting sex between a wife and her husband that is not open to procreation builds up their love for each other and helps produce a loving relationship in which it is best to bring up children. Think again Church!