New Lateral Flow Method Offers Peace of Mind for Breastfeeding Mothers with Multiple Sclerosis (MS)

Mitigating MS Relapse during Early Postpartum

Up to 30% of women with MS experience disease relapse within the first 3 months postpartum, particularly in cases of significant disease activity prior to pregnancy (Krysko et al., 2019, Capone et al., 2022). In efforts to avoid relapse, postpartum mothers might be suggested disease-modifying therapies (DMTs) (Capone et al., 2022). Due to limited data on DMT secretion into breastmilk and the impact on infant exposure, however, breastfeeding while taking DMTs is unlicensed (Capone et al., 2022). As breastfeeding offers unmatched health, physical, and psychological benefits to both the baby and mother, the decision between either taking DMTs to mitigate MS relapse or breastfeeding is heavily weighed by both mothers and physicians (Capone et al., 2022).

One class of DMTs, corticosteroids, can be taken to minimize risk for MS relapse (Almas et al., 2016). These drugs regulate gene expression, modify metabolism, and have therapeutic effects due to anti-inflammatory properties (Almas et al., 2016). Based on limited available data, it has been noted that corticosteroid drug levels in breastmilk are, while present, within the recommended “safe” range of 0.25 mg/kg/day (Cooper et al., 2015). Although it could be reasonable to continue breastfeeding while taking these drugs under low doses, mothers wishing to further limit infant exposure should withhold breastfeeding for 8-12 hours, particularly after a high intravenous dose (Almas et al., 2016).

Quantifying DMT Secretion into Breast Milk through Liquid Chromatography-Mass Spectrometry (LC-MS)

In researching the secretion of corticosteroids into breast milk, breast milk samples (following DMT therapy) were frozen and shipped to laboratories for quantification by liquid chromatography-mass spectrometry (LC-MS) (Cooper et al., 2015). LC-MS is a technique that separates compounds in a liquid sample and provides information on molecular weight, structure, and purity (Basics of LC/MS - a primer, 2025). Samples are prepared and their individual ions, based on chemical properties, travel through a column to a detector at different rates (Basics of LC/MS - a primer, 2025). As the ions reach the detector, identifying information is gathered (Basics of LC/MS - a primer, 2025).

While LC-MS is highly accurate and provides valuable information, samples need to be sent to a lab, kept under specific conditions until testing, and prepared manually using intensive methods. The instrumentation itself is costly; it can only be run (with results interpreted) by competent scientists, and run time, as well as result-reporting time, are factors to consider. This in mind, an alternative lateral-flow assay (LFA) could help mitigate costs, time, and convenience for testing DMT secretions in breastmilk.

Lateral Flow Assay Applications in Enhancing Patient Experience

Figure 1: Lateral flow assay workflow showing the collection, binding, and interpretation steps. Created by research group in Canva, 2025

Lateral-flow assays (LFAs) are paper-based devices requiring minimal equipment and training while providing relatively rapid results (under 30 minutes) (Koczula & Gallotta, 2016). With little to no additional training, breastfeeding mothers could test their breastmilk at their convenience before resuming breastfeeding, receiving results in real time.

Traditionally, LFAs are used to test for individual-specific compounds, providing qualitative results for the target compound, albeit with occasional false positives due to lower specificity compared to other laboratory techniques (Team, 2024). LFAs could test breast milk for macrolides to ensure that breastfed infants do not absorb macrolides that have not yet been fully eliminated from the milk supply (Raysyan et al., 2020). LFAs that identify these drugs in breast milk could help clinicians counsel patients considering restarting or continuing DMT treatment on whether breastfeeding can be safely resumed (Raysyan et al., 2020).

LFAs provide ‘yes’ or ‘no’ results without providing quantitative measurements (Team, 2024). LFAs operate by adding a liquid sample (in this case, breast milk) dropwise to a sample pad, which initiates capillary action (Team, 2024). As the sample migrates along the testing strip, it encounters a labeled antibody that binds to the target analyte in the milk sample (only if present), forming a complex (Team, 2024). This complex would then travel to a secondary antibody, forming a visible line that would be read as a “positive” for detectable DMT levels in the breastmilk (Team, 2024).

Figure 2: Result interpretation of lateral flow assay (LFA) tests. The presence of only the control line is a negative result. The presence of the control line and any detectable test line is a positive result. The lack of a control line is a voided result. (Steward, 2024)

As several DMTs are safe for infant consumption via breastmilk within an acceptable concentration limit, the development of LFA tests that  quantitatively measure the concentration of these particular DMTS over the acceptable limit would be most beneficial. To achieve truly quantifiable results, quantitative lateral flow assays use advanced labels that produce strong signals and precise detection systems (Sajid et al., 2015). The signal intensity corresponds to the amount of analyte captured at the test line. Magnetic particles or fluorescent materials, such as quantum dots and up-converting phosphors, are used to generate signals for specialized readers (Khreich et al., 2008).

“Safe” Limits for Corticosteroids DMTS in Breastfeeding Mothers’ Milk Supply

Of the DMTs taken by breastfeeding women with MS, methylprednisolone and prednisone are two of the most widely used, being first-line medications generally considered safe for breastfeeding mothers and infants.

The level of methylprednisolone transfer into breast milk has been shown to be lower than the generally accepted value (Boz et al., 2018). As methylprednisolone therapy is of short duration, infant exposure would be safe should a mother choose to breastfeed as soon as 1 hour after drug infusion, depending on the original drug dosage (Boz et al., 2018). Waiting 2-4 hours after the infusion would further limit infant exposure (Boz et al., 2018).

The levels of prednisolone have been shown to peak in breast milk two hours after therapy doses, declining rapidly thereafter (Ost et al., 1985, Ryu et al., 2018). It has been shown that milk concentrations were safe for infant consumption for up to 12 hours, depending on the initial dose of medication (Ryu et al., 2018).

While these drugs remain in the milk supply for several hours, albeit within safe concentration limits for infant consumption, developing quantifiable LFAs that reassure the breastfeeding mother that the milk supply is within safe limits before resuming breastfeeding would be extremely beneficial. This would offer peace of mind to the mother, allowing her to resume breastfeeding at her convenience after an LFA performed at home. This would enable the benefits of breastfeeding to both the mother and baby while also avoiding the inconvenience, time, and costs of submitting a milk sample for testing methods such as LC-MS analysis.