This isn't an example of crazy human behavior but of the stunning ways that nature assumes power over mating choices in animals. Since we are animals it pays us to take a look at what occurs in other species even though we like to think of our choices as being more conscious (despite what we know about, say, scent playing a potentially significant subconscious role in who we see as the love of our lives - or at least the flavor of the month).
A recent study from researchers at the University of Michigan on gelada monkeys shows that female geladas will spontaneously abort a pregnancy when a new dominant male comes into power over the group. The Bruce Effect, named after Dr. Hilda Bruce who studied this phenomenon in lab mice in the 50's, was thought to possibly be a result of lab conditions but a recent study of geladas in the wild found that it happens in nature as well. Detailed on io9's Gelada Monkeys Offer Evidence that Abortion is Part of Evolutionary Fitness by Robert T. Gonzalez, the study found that the birth rates plummeted in groups where new males had just taken power and that pregnant females were spontaneously miscarrying. The researchers hypothesized that rather than carry a pregnancy to term - only to have the offspring possibly killed by the new male leader - the females would spontaneously miscarry, thereby becoming fertile again more quickly and better able to produce offspring with the new male in power faster, offspring that would be able to survive.
Not exactly happily ever after, is it? And The Bruce Effect "almost certainly does not exist in humans," Gonzales writes but it might help us understand "pregnancy success rates across a variety of species - humans included."