Taking birth control pills during pregnancy is safe, but there is no benefit to it, explains Mayo Clinic. Minipills or combination birth control pills don't appear to increase birth defect risk, but there is increased risk that the fertilized egg will implant outside of uterus, resulting in an ectopic pregnancy.
If a woman suspects she is pregnant while taking birth control pills, she should stop taking the pill until the pregnancy is confirmed or ruled out. Some research has suggested there is a link between usage of birth control pills close to conception with increased risk of low birth weight, congenital urinary tract abnormalities or preterm delivery. However, the link has not been observed in any clinical trials, says medical expert Roger W. Harms from Mayo Clinic.