Answer:
If you continued taking your birth control pill because you didn't realize you were pregnant, don't be alarmed. Despite years of this accident happening, there's very little evidence that exposure to the hormones in birth control pills causes birth defects.
Still, the birth control pill is a potent estrogen. Lessons learned from women who took diethylstilbestrol - a synthetic estrogen that was later linked with cancer - to prevent miscarriage in early pregnancy suggest that such exposure should be minimized.
Once you learn that you're pregnant, stop taking the birth control pill.