Would you still get withdrawal bleeding on placebo week if you become pregnant on the pill?

No: Withdrawal bleeding stops after a woman gets pregnant, even if she keeps taking BC pills. However, pregnancy-related spotting or bleeding happens in some pregnancies... which means a woman might think she is having breakthrough bleeding or withdrawal bleeding when in fact she is pregnant. Thus, if she misses a second withdrawal period, or has other pregnancy symptoms, she can do a pregnancy test.