- Pregnant females may be eligible. There are no studies of the safety or efficacy of rifabutin in pregnant women. Rifabutin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. In addition, a risk/benefit decision should consider the likelihood of a woman's developing MAC if she does not receive prophylaxis. The risk of developing MAC rises substantially for women with CD4 counts less than 100, although it can also develop in women with higher CD4 counts. Women of reproductive potential who are not pregnant must use contraception. They are encouraged to use means other than oral contraceptives.