- Women must not be pregnant or breastfeeding because this study involves an investigational agent whose genotoxic, mutagenic, and teratogenetic effects on the developing fetus and newborn are unknown; women of childbearing potential who are sexually active, must use 2 accepted methods of birth control at the same time for 4 weeks prior to lenalidomide treatment, during lenalidomide treatment, and up to 4 weeks after lenalidomide treatment is finished; sexually active males must use a latex condom for contraception during the study and up to 4 weeks after treatment with lenalidomide has ended