Hello, that is a very good question!
Back then there was no such thing as 'birth-control', hence they never actually prevented pregnancies, of course there were services that provided 'different' penetration but that could also result in pregnancies.
The popular method of not giving birth [prevent pregnancy] was to kill the baby while still carrying [termination], in other words have a miscarriage.
There many various methods during that time (herbs, beating, old cloth hanger).
Hope this helped,
j548831