Cellcept, a drug used in heart, liver, and kidney transplant patients, has been linked to miscarriages and birth defects in female users of child-bearing age, according to the FDA. Cellcept, an immunosuppressant drug, already carries a black box warning is designed to keep the immune system from attacking the new organ. Roche, the manufacturer of Cellcept, has sent a letter to health officials, urging women to obtain a negative pregnancy test prior to beginning a regimen of Cellcept.