This section explains how relapse is managed during breastfeeding and provides detailed guidance on which DMTs are safe (or not safe) to use while breastfeeding.
Will I be able to breastfeed after delivery?
Yes, I see no reason why you can’t breastfeed if you have MS. However, certain DMTs cross over into the breast milk and may affect the baby; these include teriflunomide, cladribine and S1P modulators (fingolimod, siponimod, ozanimod and ponesimod). Although monoclonal antibodies (natalizumab, ocrelizumab, ofatumumab, rituximab) cross over in small amounts, the levels are generally too low to affect the newborn. In addition, the level of the antibodies will likely be further reduced by their digestion as proteins in the baby’s intestinal tract.
Please be aware that most DMTs are licensed with no breastfeeding safety data. Hence, the information in the manufacturer’s Summary of Product Characteristics (SmPC) is not the same as that given to you by neurologists and other HCPs. For example, SmPC information for the fumarates (dimethyl fumarate and diroximel fumarate) states:
“It is unknown whether dimethyl fumarate or its metabolites are excreted in human milk. A risk to the newborns/infants cannot be excluded. A decision must be made whether to discontinue breastfeeding or to discontinue Tecfidera therapy. The benefit of breastfeeding for the child and the benefit of therapy for the woman should be taken into account.”
This is very unhelpful as their active compound, monomethyl fumarate, is a naturally occurring metabolite compounded with many other medications considered safe in pregnancy, e.g. ferrous fumarate, an iron supplement. This is why I tell my female patients on fumarates they can breastfeed without concern for their baby.
We normally don’t recommend alemtuzumab treatment during breastfeeding simply because it carries the risk of listeriosis and infusion reactions, and the medications used to prevent these adverse events cross over into breast milk. In addition, the acute immunosuppression associated with alemtuzumab may increase the risk of breast infections. In general, I advise my female patients to breastfeed for 4 ̶ 6 weeks to give the baby the health benefits of breastfeeding and then to start or be retreated with alemtuzumab after this period.
For cladribine, it is important not to breastfeed whilst being dosed with the drug and for 10 days after the last pill. The recommended 10-day requirement is probably a bit long as cladribine is undetectable in the body after 48 ̶ 72 hours. In my experience, the requirement of a 14- or 15-day gap (4 or 5 days of dosing plus an additional 10 days) in breastfeeding is hard; therefore, most women who want to be treated with cladribine either delay treatment until they have completed breastfeeding or breastfeed for 4 ̶ 6 weeks before stopping and being treated with cladribine.
| Disease-modifying treatment | Guidance |
| Alemtuzumab | Not recommended during breastfeeding; consider breastfeeding for 4 ̶ 6 weeks before restarting alemtuzumab treatment |
| Cladribine | Crosses over into the breast milk and may affect the baby. Do not breastfeed whilst taking cladribine and for 10 days after the last pill; consider breastfeeding for 4 ̶ 6 weeks before restarting cladribine treatment |
| Fumarates (dimethyl fumarate, diroximel fumarate) | The manufacturer’s licence recommends caution; however, monomethyl fumarate, a naturally occurring metabolite of the fumarates, is compounded with other medications that are considered safe in pregnancy |
| Monoclonal antibodies (natalizumab, ocrelizumab, ofatumumab, rituximab) | Cross over into breast milk in small amounts, but at low levels that do not generally affect the newborn |
| S1P modulators (fingolimod, siponimod, ozanimod, ponesimod) | Cross over into the breast milk and may affect the baby |
| Teriflunomide | Crosses over into the breast milk and may affect the baby |
Guidance for women who are considering whether it is safe to breastfeed while taking a specific DMT.
I am aware that many women feel pressured into breastfeeding. However, if you are anxious about having MS rebound post-partum, deciding not to breastfeed and starting or resuming your DMT as soon as possible is not unreasonable. The decision is a personal choice.
How is a relapse managed during breastfeeding?
In the event of a relapse during breastfeeding, a short course of high-dose corticosteroids can be considered. Methylprednisolone – the steroid often used to manage MS relapses – is transferred into breast milk. However, the amount an infant is exposed via breast milk is low (equivalent to less than 1% of the adult dose). Some clinicians recommend women breastfeed before a steroid infusion, express breast milk 1 ̶ 2 hours after the infusion and discard it, to limit the baby’s exposure to methylprednisolone. I don’t think this is necessary.
References
Krysko KM et al. Treatment of women with multiple sclerosis planning pregnancy. Curr Treat Options Neurol 2021;23:11.
Other articles in this series on Pregnancy and childbirth
Planning for pregnancy
Managing MS during pregnancy
Preparing to give birth
Concerns about parenting