No, morning after pill will not harm your developing fetus. Morning after pill is not known to cause any fetal birth defect after failure of emergency contraception. So relax and don’t worry. You must have stopped Tetralysal which you had been using for treatment of acne. If not, then immediately stop using it. Tetralysal is known to cause fetal birth defects if taken during pregnancy. Do not take any medicine unless suggested by your obstetrician. Many medicines are known to cause fetal birth defects if used during pregnancy, for which you might not be aware. Take medicines if suggested by your obstetrician. Thanks