so i've often talked with friends about birth control pills making people crazy (myself included, so i've been off for years), but this book i'm reading about smell just confirmed some scary ideas about wedded bliss...the author says you should go off the pill if you're looking for your mate!
the pill changes your ability to smell someone who is a good mate (women chose men based on their MHC, or major histocompatibility complex, over 50 genes strung together along a single chromosome, which is the genotype for your immune system) we pick someone similar but not exactly matched to our immune system, so that we make the best possible offspring who will not be picked off by natural selection. but the pill makes your body think you're already pregnant, so you're going to be attracted to people with your own familial smell, or same MHC, because you're not trying to procreate physiologically since you're already pregnant (at least your body thinks so)
so then the man you chose smells a certain way while you're on the pill. but say you both decide you WANT to get pregnant? so you go off the pill and he smells completely different now. his MHC is so much like yours that maybe you're less sexually interested (because now he smells like your brother, which you didn't notice before because your body liked that, it wasn't really into procreation while it thought it was already pregnant)
and then the author went on to talk about how this can really mess with people being attracted to each other! maybe you weren't on the pill when you started dating, or even when you first got married, but then it just seemed easier? and now that you're on it, your husband just doesn't smell the same to you, you're just not that into him?