- The effects of ipilimumab on the developing human fetus are unknown. For this reason and because ipilimumab was found to have teratogenic and abortifacient effects in animal studies, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 4 months after the last injection of ipilimumab. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately.