How do you counsel women on anti-CD20 therapy for MS who are planning for pregnancy?

I counsel patients that anti-CD20 therapies are relatively safe in patients with MS who are considering pregnancy. Monoclonal antibodies are not transported across the placenta until the 2nd trimester, and with a half-life of 20-30 days (depending on which anti-CD 20 is used), the amount that crosses the placenta is very small, even if conception occurs shortly after treatment exposure. If there is exposure later during the first trimester, then there is potential for B-cell depletion in the new...