- Because FdCyd has been shown to be teratogenic in animals, pregnant women are excluded from this trial. Nursing women are also excluded, as there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with FdCyd. Women of childbearing potential must agree to either abstain from sexual intercourse or use two forms of acceptable birth control, including one barrier method, for 4 weeks prior to study entry, for the duration of study participation, and for 3 months after completion of study. Men must use a latex condom every time they have sexual intercourse during therapy and for 3 months after study completion, even if they have had a successful vasectomy. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she or her partner should inform the treating physician immediately.