Generally, taking birth control pills early in pregnancy does not cause significant problems. Although it is not recommended, this situation is quite common among women who become pregnant unintentionally.
The American College of Obstetricians and Gynecologists states that taking birth control pills during pregnancy does not increase the risk of birth defects. However, a 2009 study indicated that taking birth control pills during pregnancy might increase the risk of low birth weight or preterm birth. Additionally, certain birth control pills might cause developmental issues with the genital organs of female fetuses.
If you suspect you are pregnant, you should stop taking birth control pills as soon as possible.