Disease activity during pregnancy in a modern MS cohort

Women with relapsing-remitting MS treated with moderate- or high-efficacy disease-modifying treatment (DMT) are at greater risk of relapse during pregnancy [1]. Apparently, immunomodulatory changes during pregnancy are not sufficient to suppress MS disease activity among these women. This is of great clinical interest because pregnancy has historically been associated with a reduced risk of relapse.

The presented study aimed to compare the characteristics and relapse rates of a modern cohort of women on different classes of DMT (low-, moderate-, and high-efficacy) before conception, and to determine factors that predicted relapse. The study included data of 1,640 pregnancies in 2011-2019, conceived from 1,452 women. DMT use in the year before conception was no DMT (n=346), low-efficacy (n=845), moderate-efficacy (n=207), and high-efficacy (n=242).

EDSS ≥2 at the time of conception was more common in higher-efficacy DMT groups (high-efficacy DMT 41.3%, no DMT 20.2%). Annualised relapse rate (ARR) in the year prior to conception was relatively similar in the 4 DMT groups, averaging 0.29. ARR slightly decreased during pregnancy in the no-DMT or low-efficacy DMT groups, but steadily increased throughout in the high-efficacy group (0.42 vs 0.14 on low-efficacy, in third trimester). In the moderate-efficacy group, ARR increased in the first trimester (0.55 vs 0.14 on low-efficacy), then decreased to a trough in the third. In the first trimester postpartum, there was a spike in ARR in all groups, which was highest in the moderate- and high-efficacy groups (see Figure). Pre-conception ARR and preconception use of medium- or high-efficacy DMT predicted relapse activity during pregnancy. Continuing high-efficacy DMT into pregnancy predicted reduced relapse risk (OR 0.80), as did older age (≥35 years).

Figure: Annualised relapse rate by DMT class

The authors concluded that careful pregnancy management and use of long-acting high-efficacy DMT pre-conception, or continuing high-efficacy DMT into pregnancy beyond the first trimester, may prevent relapse in pregnancy.

1. Yeh W, et al. Pregnancy in a modern day multiple sclerosis cohort: Predictors of relapse during pregnancy. MSVirtual 2020, Abstract PS12.04.