To explore sNfL levels during pregnancy and puerperium in MS patients and healthy controls.

In Multiple sclerosis (MS), the annualized relapse rate (ARR) is reduced during pregnancy and temporarily increased in the puerperium. Neurofilament light chain (NfL) is a highly specific structural protein of neurons and its quantification in serum is considered a biomarker for neuroaxonal injury. NfL levels in blood are associated with relapse activity, disability scores and treatment response in MS. 

Prospective, longitudinal, single-center study. sNfL concentration was assessed using SIMOA test during pregnancy (first and third trimesters) and in puerperium (P), in a cohort of 35 pregnant patients with relapsing multiple sclerosis (P-MS).

Twenty five non-pregnant MS patients (NP-MS) and 21 healthy pregnant women (HPW) served as control groups. Eight R-MS patients suffered relapses during pregnancy (RP-MS) always in the first or second trimesters.

No differences in pregnancy and delivery data were observed between P-MS and HPW. No differences in the EDSS score, relapse rate or age were observed either between P-MS and NP-MS.

P-MS patients showed higher sNfL values than HPW in the first trimester, independently of the presence (p=0.002) or not (p=0.02) of relapses. However, in the third trimester, only RP-MS showed higher sNfL values than HPW (p=0.001). No differences were found in sNfL between RP-MS and NP-MS. By contrast, P-MS patients not suffering relapses showed lower values than NP-MS at first (p=0.006) and third (p=0.001) trimesters and during puerperium (p=0.001).  

 These data strongly suggest that sNfL levels can be useful for monitoring MS activity during pregnancy. Additionally, the absence of relapses during pregnancy may have a beneficial effect on neurodegeneration during puerperium.