Now that gets into Brave New World territory. They didn’t make it illegal (at least that I recall)… but it was a taboo to be part of a family. Some point in British society started using eugenics to create humans. Sexual promiscuity was expected among women (they hinted that monogamy was also taboo) but becoming a parent was no go.

EDIT: I wouldn’t recommend Brave New World. Huxley falls in line with contemporary beliefs about indigenous Americans that is downright racist today.