Health Canada says that women who are pregnant or may become pregnant should avoid modafinil, reports the CBC.

“The frequency of major congenital anomalies (17.3 per cent) and cardiac anomalies (4 per cent) associated with the exposure to modafinil and/or armodafinil was above the frequency observed in the general population (3 per cent and 1 per cent, respectively,” Health Canada said in its letter on Thursday.