MS activity and pregnancy outcomes after long-term use of natalizumab

Discontinuing natalizumab during the first trimester of pregnancy increased the relapse risk during pregnancy and postpartum. Continuing natalizumab after the 30^th gestational week significantly reduced postpartum relapse risk, but also increased anaemia in newborns.

A prospective, observational cohort study assessed relapses during pregnancy and postpartum as well as pregnancy outcomes, including foetal haematological abnormalities, in women with highly-active MS who used natalizumab [1]. Patients were divided into 2 groups: those who terminated natalizumab during the first trimester (1 Trim-group) or after the first trimester (>1 Trim-group). Prof. Sandra Thiel (Ruhr University Bochum, Germany) presented the results [1].

Included were 350 pregnant women, 171 in the 1 Trim-group and 179 in the >1 Trim-group. The latter group stopped natalizumab after a median of 31 gestational weeks (range 12.1–39.7 weeks). Women in the >1 Trim-group had significantly fewer relapses during pregnancy (5.2% vs 32.4%; P<0.001) and postpartum (22.8% vs 49.7%; P<0.001) compared with the 1 Trim-group (see Figure). Early restart (4 weeks postpartum) also decreased the relapse risk postpartum (OR 0.32; 95% CI 0.17–0.58; P<0.001).

Figure: Relapse rate during pregnancy and postpartum [1]



Tri, trimester; 1 Trim-group, natalizumab terminated during the first trimester; >1 Trim-group, natalizumab terminated after the first trimester.

Pregnancy outcomes were similar between groups. In the >1 Trim group and the 1 Trim group, 12.9% and 10.6% of births were preterm (P=0.625), while 4.7% and 3.4% of newborns had congenital abnormalities (P=0.719). In both groups, newborns were smaller than expected. To assess anaemia and thrombocytopenia in the 122 newborns with available blood counts, the >1 Trim group was stratified into women who stopped natalizumab after gestational week 30 (>30GW; n=79) and before week 30 (<30GW; n=43). Compared with the <30GW group, newborns in the >30GW group had significantly more often haematological abnormalities (57% vs 39.5%; P=0.10). Rates of anaemia were 46.8% and 27.9%, for <30GW and >30GW respectively; rates of thrombocytopenia were 22.8% and 16.3%. Significantly more women in the <30GW group suffered from relapse (38.5% vs 16%), especially during the first postpartum trimester.

Prof. Thiel concluded: “These study results should lead to a risk-benefit discussion between women treated with natalizumab and their neurologists, to continue treatment up to week 30 or even week 34 of gestation, in combination with an early restart during the first 4 weeks after delivery.”

1. Thiel S. Disease activity and pregnancy outcomes after long-term exposure to natalizumab during pregnancy. Abstract O039, ECTRIMS 2022, 26–28 October, Amsterdam, the Netherlands.

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Posted on 20 December 2022