Acnetane (isotretinoin) needs 42 hours to leave the system. Women who may become pregnant must use 2 effective forms of birth control at least 1 month before starting therapy, during therapy, and for 1 month after stopping the medicine. Your health care provider should conduct pregnancy tests on a monthly basis while you are taking isotretinoin. You should really stop taking this if you are planning to get pregnant or already pregnant. Tretinoin containing products should not be used by pregnant women. Serious and sometimes fatal birth defects can occur if taken during pregnancy. You should choose 100% natural products instead or non-hypoallergenic products.