Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Norethisterone used during the first trimester of pregnancy may be associated with congenital malformations in male and female fetuses and virilization of the external genitalia of the female fetus. It is classified category x by us fda, studies in animals or humans have demonstrated fetal abnormalities and/or there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the risks involved in use of the drug in pregnant women clearly outweigh potential benefits. Hope I have answered your query. Let me know if I can assist you further.