The U.S. Food and Drug Administration released a statement on Friday warning that certain immune-suppressing medications can cause miscarriage and birth defects.

According to the FDA, the drugs causing birth defects include Roche’s CellCept and Novartis’ Myfortic. They are approved for use by organ transplant patients to prevent organ transplant rejection, but sometimes they are prescribed for unapproved uses to treat other immune system disorders such as lupus, rheumatoid arthritis and erythema multiforme.

The FDA said reported birth defects included serious congenital anomalies such as cleft lip and palate and ear deformities.

In October, both drugs were labeled with a black box warning about the risk of miscarriage during the first trimester and birth defects in babies born to women who take the drugs while pregnant. The following month, the labels were changed warning strongly on the negative effects when given to pregnant women.

The FDA spokesperson Christopher Kelly explained that the agency decided to issue a new alert about these two drugs because some physicians who prescribe the drugs for unapproved uses may not have noticed the labeling change.

The FDA wrote in its statement that, before prescribing the drugs, doctors should confirm their transplant patients are not pregnant and, are using effective contraception.

The agency also said it would continue working with Roche and Novartis to reduce use of both drugs by pregnant women.

Last month, the FDA announced it was investigating 16 patients who developed a rare neurological disease, namely progressive multifocal leukoencephalopathy, while taking the drugs. PML attacks the brain and central nervous system and is usually fatal. According to the FDA, patients who survive this disease are often permanently disabled.