My son's a devout Catholic and is engaged. They are planning to use the "natural family planning" method, which sounds like a load of crap to me. He says the method is claimed to be "97.5% effective". So I pointed out that newlyweds typically have sex more than 100 times in a year, so what does that do for the probability of a pregnancy during the first year? I also said that each religion has a point at which it fails to serve its adherents, and this is one of them. I also recalled that when I was growing up we always knew who all of the American Catholic familes were because they had 5 to 12 kids.
I had some other thoughts, but didn't want to carry on too much about it, just point out a few obective facts.
My wife and I are Catholic and when we were going through our interviews with the priest prior to marriage, we raised the objection that we cannot agree with the church's position on birth control. In not so many words, said that the old idea was to go forth and populate the earth, and we did that. And he left it at that. Very tactful, I think, because it didn't compromise his duty to the church.
I would hate to see this couple burdened with a bunch of kids, especially since they are marrying young.