If you are already pregnant (even if you do not know it yet), EC will not work. EC can only prevent a pregnancy from starting; it cannot stop one that already has. And if you accidentally take EC before you know you are pregnant, it will not hurt you or the pregnancy.
References:
- “What’s the Difference? The Abortion Pill vs. Emergency Contraception.” Carafem, https://carafem.org/ec-vs-abortion-pill/ Accessed March 2024