MS & Pregnancy: What's Safe?

Infusions and injections (monoclonal antibodies). The approved monoclonal antibodies include natalizumab, alemtuzumab, and daclizumab. (Currently, use of rituximab in MS is off label, and the FDA is reviewing the efficacy and safety data for ocrelizumab.) The monoclonal antibodies are category C. The recommendation is to discontinue natalizumab one to two months prior to conception and discontinue alemtuzumab four months preconception.¹⁰ There is no evidence of spontaneous abortion or birth defects in women on alemtuzumab, but there is potentially increased risk for spontaneous abortion in those on natalizumab.

The spontaneous abortion rate in daclizumab-exposed women is consistent with early pregnancy loss in the general population (12% to 26%). Data on a small number of pregnancies exposed to daclizumab did not suggest an increased risk for adverse fetal or maternal outcomes.¹¹ However, the recommendation is to discontinue daclizumab four months prior to conception. Rituximab should be discontinued 12 months prior to conception, based on the manufacturer recommendation, although it is potentially safe to conceive when the B cell counts return to normal.

Chemotherapy agents. Mitoxantrone is the only FDA-approved chemotherapeutic drug used in MS. However, a few chemotherapy drugs—among them, azathioprine, methotrexate, and cyclophosphamide—are used off label. Chemotherapeutic agents are category D, except methotrexate (category X). Women on category D medications must use a method of birth control for three months after stopping the DMT. Often, clinicians will recommend women initiate GA or interferon during this period, in the hope of minimizing disease activity. Women on mitoxantrone and methotrexate need to use birth control for six months after stopping these immunosuppressive medications, before conceiving.¹² These women likely need to switch to a safer pregnancy DMT during the long washout period.

Pregnancy and breastfeeding among women with MS require planning and decision making. The recommendations differ among clinicians and MS experts since there is no definitive evidence about the risks of the DMTs on the mother and/or the fetus. Clinicians should discuss the potential risks with women based on their knowledge and experience, and the data available based on animal research and the pregnancy registries. —ABB-Z

Aliza Bitton Ben-Zacharia, DNP, ANP
President-Elect of IOMSN
Neurology Faculty, Icahn School of Medicine, Mount Sinai Hospital System, New York, New York