>>150177706
Women are biologically conditioned to desire different partners when pregnant due to the innate vulnerability involved. This also has some interesting psychological effects, like apparently women are drawn to men that more closely resemble family when pregnant, possibly some ancient tribal protection instinct: when you are looking to get pregnant, you are drawn to genetic diversity (not racial per se, just men with some distance from you genetically as a pressure against inbreeding), but afterwards you return to your tribe for the actual support during the pregnancy.
Because modern birth control is primarily via the hormonal route, it works by constantly signaling to a woman's body that she is pregnant. This means her brain is always in "find a familiar non-threatening man" mode without her consciously being aware of it.
What happens, then, when they marry/settle down with a guy while on artificial pregnancy brain and then stop taking birth control to get pregnant for real is that their subconscious defaults back to the natural partner-seeking state, which makes them attracted to more masculine, less familiar men. Their sexual interest in their husband wanes because they were essentially "high" on pregnancy hormones all their life since they've been taking fake ones since middle school, and with the sexual attraction removed it kills the relationship and nobody is sure where the "spark" went.