The Pill took a lot of risk out of it. Plus there was the free love of the sixties. Cheating didn’t start there, but it ramped up sharply.
Antibiotics and sulfa drugs took a lot of the risk out of it.
before that, even a yeast infection could become fatally septic.
It is estimated that between one quarter and one third of all women who lived before modern medicine died from some complication relating to their reproductive system, not necessarily involving a pregnancy.
Read a stat that a British researcher found that 25% of all children born during the war years, were sired by another man (not their legal father). Think about that. There was no "Pill" then. And even if you try to discount for the absences caused by husbands serving overseas, it's still a helluva number.