“It is contraception.”
It’s the Pill. That was the first nearly 100% contraceptive, legalized abortion would never have come about except as a back-up to the 95% (off the top of my head) effective birth control pill.
I don’t say this as proof, but let me add that I once said this to an adamantly pro-choice friend, truly a woman of the Left, and she agreed with me straight away.
Great philosophers have said abortion is the result of birth control/the pill. Cultural acceptance of it