Breastfeeding and multiple sclerosis

Here is My Question:
Hello,

I am a 35 year old mother of a 7.5 month old baby born last June. In April of 2021 I was diagnosed with Clinically Isolated Syndrome which I understand means that I’ve only had one episode of MS. (Which was optic neuritis, which made me temporarily blind in one eye)

I was subsequently on Glatopa until I got pregnant in September of that year, and have been off medication while had the baby and was breastfeeding until yesterday, Feb. 10th, when I received a transfusion of Truxima 500mg.

What I want to know is how long should I wait until it is safe to breastfeed again? And when will it be safe to start trying to get pregnant again?

Thank you for your help!

Answer:
The safety of breastfeeding in people with MS after a rituximab infusion (or any of the anti-CD20 monoclonal IgG antibodies) was recently published in case series in the Journal of Neurology, Neurosurgery and Psychiatry, a British medical journal. Similar data was presented at last year's American Academy of Neurology Meeting.

The data collected shows that shortly after (even within days) a rituximab infusion, there is minimal rituximab found in breast milk and no evidence that the small amount present in breast milk is absorbed in the GI tract of infants or lowers their B cell counts. 

This result makes a lot of sense; most IgG antibodies are transferred from the mother to the infant prior to birth. During the first 2 weeks of breast feeding, the breast milk, called colostrum, is higher in antibodies than the subsequent breast milk, so we would not recommend antibody therapies like rituximab during this period. 

Most of the antibodies transferred in breast milk are IgA antibodies (over 90%) with IgG antibodies representing only 5 to 6% of immunoglobulin. Since rituximab and all other anti-CD20 monoclonal antibodies are IgG antibodies, very little is transferred to human breast milk in the first year of breast feeding. The amount of IgA and IgG in breast milk increases somewhat in the second year of breast feeding but it is less common to breast feed this long in the US.

Any Rituximab IgG in breast milk is quickly digested by the lower pH in the stomach and digestive enzymes. Remember, IgG is just a protein source, and it will not be active unless absorbed intact into the blood stream. In normal circumstances this is unlikely

There are possible exceptions to this rule. If you have a premature infant or an infant with a GI tract disorder, they may absorb enough rituximab to lower B cell counts at least temporarily. It is unknown if this is the case or if it is the true, this would be harmful

We have successfully treated women with MS breast-feeding post-partum with both rituximab and ocrelizumab to prevent post-partum relapses in high-risk patients. We wait 2 to 3 weeks to allow the mother to recover from the delivery and get used to breast feeding. While the numbers in our experience are small (less than 10), this has been well tolerated and effective. We do not treat mothers with post pregnancy complications or with premature infants. 

Overall, there is no consensus yet on this issue. Our policy in medicine has always been to avoid medications in mothers during pregnancy or post-partum when breast-feeding unless the benefits outweigh the risks. This is something you will have to decide after weighing the risks and discussing further with your MS specialist.

If you have fewer risk factors for post-partum relapses, then you may want to just pursue exclusive breast feeding. There is some mounting evidence that exclusive breast feeding may lower the risk of post-partum relapses; but remember, exclusive breast-feeding means while the infant receives no other nutrition other than breast milk.

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