Kills who? Fetuses? There shouldn't be a goddam fetus if someone's taking the Pill.
Supposedly the Pill kills women.
How?
If your brain's starved enough of intelligence, you'd probably be stupid enough to eat a whole pack in a day, which likely
would kill you. Otherwise, aside from side effects which occur with any hormone-based drugs, they're perfectly safe.
That, or like Kefka said, they're going under the delusion that zygotes are people. In which case, they're not only devoid of intelligence, but their brains are in danger of collapsing in on themselves.