Moderate to severe acne may require the use of systemic medications, which are used internally. These medications are highly potent but many of them are not suitable for use during pregnancy since they pose risk of birth defects. Hormone therapy with estrogens or ant-androgens can be used to treat acne associated with hormonal imbalances. These should not be used during pregnancy and breastfeeding. Isotretinoin is an anti acne medication which is contraindicated for use during pregnancy. This medication can pass from the mother to the bay through the placenta. It can cause birth defects like heart defects, craniofacial defects and central nervous system defects. It also increases risk f miscarriage and fetal death. Therefore, women who are using this medication should be carefully monitored during the course of treatment. Women should be careful to avoid becoming pregnant during treatment. If at all, pregnancy does occur, the medication should be stopped immediately. Retin-A can also be passed on from mother to baby, although very small amounts of the compound actually reach the fetus. However, this drug is also best avoided during pregnancy. Whether this medication causes birth defects is not yet studied extensively. Oral tetracycline should not be used during pregnancy because it can affect bone and teeth growth in a developing fetus. Therefore, women who are pregnant or plan to become pregnant should inform their doctor before starting medications for acne.