WASHINGTON -- Health regulators are again warning that Roche and Novartis drugs prescribed to organ transplant patients can cause miscarriages and birth defects when used by pregnant women.

A Food and Drug Administration spokesman says the agency has not received any new reports of pregnancy-related problems, but was concerned some doctors may not have seen the initial warning.

In October, the agency said it received reports of miscarriages and infants born with ear and mouth birth defects after their mothers took Roche's CellCept.

CellCept and the Novartis AG drug Myfortic are used to suppress the body's immune system to avoid organ rejection in transplant patients.

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