What I have read about birth control pills (written from a naturopathic perspective) says that taking hormone pills interferes with a woman's natural selection regarding partners. Things like smell and pheromones, meaning she can actually choose someone whom she finds appealing while on the Pill, but once she comes off it, she realizes they are "incompatible." I've even heard about studies where women who are on the pill tend to choose "Beta" males, as opposed to women who are not on the pill being more prone to select "Alpha" male types. So if she is on the pill when she first gets married and suddenly stops in order to become pregnant... it makes sense that it could result in increased unhappiness with the partner she selected.
Just reinforcing that the Pill is evil in more ways than one. So many women bought into the Lie.