I had already written about the topic of pregnancy in women with mild/moderate MS in the context of this blog. In doing so, I had excluded women with highly active MS – so explicitly also women who are being treated with Tysabri (active ingredient Natalizumab). Therefore, I would like to deal with considerations on this topic now.
Patients who receive Tysabri nowadays need this medication because of an active disease. As long as the therapy is applied, the disease is usually well controlled, if the medication is discontinued, a return of disease activity can be expected from the 3rd month after discontinuation – in individual cases with very serious consequences for the affected person.
Therefore, patients who are being treated with Natalizumab and want to become pregnant have been advised for some time not to discontinue the medication before a planned pregnancy, but to maintain the medication in any case until the onset of pregnancy. Since pregnancy itself has a protective effect against the inflammatory activity of the disease in the 2nd and 3rd trimester, administration up to the onset of pregnancy has been considered sufficient in the past and therapy has only been continued during pregnancy in a few exceptional cases. However, from clinical experience we know that the protective effect of pregnancy is often not sufficient, especially in highly active MS cases, and then relapses occur during pregnancy or shortly after childbirth, which are associated with a risk of permanent damage.
Therefore, recently the continuation of treatment with Natalizumab has been recommended to women with highly active MS during pregnancy, knowing full well that the substance is placenta-permeable and thus also exposes the unborn child. However, the risk of such exposure is considered less than the risk for the untreated MS patient of suffering relapses and permanent neurological deficits without the protection of the medication.
The following procedure is currently being promoted, which is designed to keep the risks for mother and child as low as possible: Natalizumab should be continued until the 24th -30th week of pregnancy, but at 6-week intervals (mainly to minimize exposure of the fetus). In the last third of pregnancy, Natalizumab administration is then discontinued – a resumption of therapy immediately after childbirth is sought, which is also associated with the recommendation to stop breastfeeding. Tysabri passes into breast milk in a certain concentration and is therefore also absorbed by the child. Although it is extremely questionable whether this really poses a problem for the newborn, this precaution is justified in any case because of the immature intestine of a newborn. And in this overall constellation – from the mother’s point of view – the advantages of breastfeeding for the newborn take a back seat.
Women who are being treated with Tysabri and want to become pregnant should definitely discuss the possible strategies with their neurologist in advance and set a clear roadmap for the pregnancy.
