Should I stop breastfeeding to go on course of cladribine?

Here is My Question:
Hello, I am 31 and has been successfully (EDDS 0) treated since 2017 (2 years of Tecfidera, in 2019 switched to Natalizumab, in 2020 switched to Cladribine due to high level of anti JVC antibodies). 
In 2022, 12 months after completing the second course of Cladribine, I got pregnant and on the 23.06.2023 delivered a healthy boy. I am breastfeeding.
I feel well, completely asymptomatic, Still EDDS - 0
3 weeks ago, I had my routine check-up MRI which revealed two new lesions (1 of which is 6 mm GD (+).
My questions are:
1. Should I have the 3rd course of Cladribine
2. If yes, can I stop breastfeeding for 14 days, then resume or:
3. Should I stop breastfeeding and be started a new medication (I have been offered options Cladribine od Ocrevus)
I’d love to carry on with breastfeeding but I’m scared of the risk of the disease worsening

I would appreciate your advice!
Many thanks!

Answer:
Great question. The safest option- among those you mention- while breast feeding would be a single dose of Ocrevus. You could even receive a single lower dose of Ocrevus (300 mg x 1 dose). This would provide protection against recurrent MS activity for 6 months or more. Ocrevus is an IgG monoclonal antibody, and very little if any of the drug passes into breast milk. Most of the antibodies passed from the mother to child in breast milk are IgA type antibodies. We also now have several studies showing the safety of Ocrevus in breast feeding mothers. 

Remember, we pre-medicate people prior to the Ocrevus infusion with a dose of steroids and often Benadryl and Tylenol to prevent infusion reactions. Because the pre-medications may enter breast milk we recommend, pumping and dumping breast milk for at least 24 to 48  hours after the infusion.

​PLEASE NOTE: This information/opinions on this site should be used as an information source only.  This information does not create any patient-HCP relationship, and should not be used as a substitute for professional diagnosis and treatment.  Please consult your health care provider before making any healthcare decisions or for guidance about a specific medical condition.

Revere P (Rip) Kinkel, MD
Professor of Neurosciences
Director of the Multiple Sclerosis Program
University of California San Diego