Which of the following might indicate that a woman of child-bearing age should be cautious about her contraceptive method while on TB treatment?

The use of rifampin is particularly significant when considering contraceptive methods during tuberculosis (TB) treatment. Rifampin is a powerful antibiotic that is part of the standard treatment regimen for TB, and it is known to interact with hormonal contraceptives, notably those containing estrogen and progestin.

Due to rifampin’s induction of liver enzymes, it can decrease the effectiveness of certain hormonal contraceptives, potentially leading to unintended pregnancies. Women of child-bearing age should therefore exercise caution and may need to consider alternative contraceptive methods or additional precautions to ensure effective pregnancy prevention while on this medication.

In contrast, isoniazid does not have the same effect on hormonal contraceptives and is less of a concern when it comes to contraceptive efficacy. A routine vaginal examination and lack of menstrual symptoms do not directly indicate any need for caution regarding contraception in the context of TB treatment, as they are not related to the pharmacological interactions that would affect contraceptive effectiveness.