that has not been the experience of the gals i have counseled... especially Christians... and having sex outside of marriage was something they wanted to hide... they were not proud of it... they did not want it to be known... therefore, there was no way they could have a baby... i am talking about Christian girls... girls who were involved in church--not just church goers... parents were involved, friends, etc--all involved in church...
What is new in this time and place as compared with the 50s, is that shame of being a virgin is more than as the shame of being known to have had sex. Even then a boy who was a virgin was thought to be a bit odd, a Holy Joe. Girls got away with it because they could get pregnant. But underlying the shame was also a sense of guilt. If a person lacks of a sense of sin, and morals are based only on convention, then shame is more easily overcome.