No, emergency contraceptive pills ("morning after pills" or "day after pills") do not appear to cause any birth defects. Although no reliable studies have looked specifically at women who gave birth after using emergency contraception, two strong reasons exist for concluding that emergency contraceptive pills will not harm a developing fetus.

First, emergency contraceptive pills contain the same hormones as many daily birth control pills, which a number of studies have found cause no increased risk of birth defects in children born to women who continued to take them because they didn’t realize they were pregnant. As a result, the United States Food and Drug Administration removed warnings about the possibility that oral contraceptives could harm a fetus several years ago. Second, even if you don’t realize you are pregnant, you would take emergency contraceptive pills long before the organs would start to develop (a process called “organogenesis”), making it impossible for emergency contraception to lead to birth defects.