Editors' note: Pregnancy decision-making in women with multiple sclerosis treated with natalizumab: I: Fetal risks

Abstract

In “Pregnancy decision-making in women with multiple sclerosis treated with natalizumab: I: Fetal risks” and “Pregnancy decision-making in women with multiple sclerosis treated with natalizumab: II: Maternal risks,” Dr. Portaccio et al. reviewed the maternal and fetal outcomes of pregnancies in patients with multiple sclerosis on natalizumab. They found that exposure to natalizumab in the first trimester was significantly associated with higher risk of spontaneous abortion and lower fetal birth length and weight, and that patients on natalizumab had higher relapse rates during pregnancy and postpartum than control patients with multiple sclerosis who were untreated or used injectable agents. To balance maternal and fetal risks, the authors concluded that—after appropriate counseling—it is reasonable to continue natalizumab until conception and reinitiate it early after delivery. In response, Proschmann et al. believe that natalizumab should not be stopped in the third trimester due to the increased risk of disease activity in the peripartum period. Portaccio et al. respond that hematologic abnormalities have been reported in some newborns exposed to natalizumab in the third trimester, but they agree that a risk/benefit analysis must be performed when considering the timing to reinitiate therapy and that, in fact, drug continuation throughout the entire pregnancy might be appropriate for a narrow subsection of patients with severe disease. Sotgiu et al. postulate that natalizumab's effects on uterine natural killer cells may make it harmful to fetuses; Portaccio et al. respond that, based on the available data, it is not clear that natalizumab should be considered teratogenic. Drs. Portaccio and Amato, Proschmann et al., and Sotgiu et al. all believe that further investigation of the pharmacokinetics and pharmacodynamics of natalizumab in pregnancy and the effects of in utero exposure to natalizumab on fetal growth, maturation, and neurodevelopment is warranted. In “Pregnancy decision-making in women with multiple sclerosis treated with natalizumab: I: Fetal risks” and “Pregnancy decision-making in women with multiple sclerosis treated with natalizumab: II: Maternal risks,” Dr. Portaccio et al. reviewed the maternal and fetal outcomes of pregnancies in patients with multiple sclerosis on natalizumab. They found that exposure to natalizumab in the first trimester was significantly associated with higher risk of spontaneous abortion and lower fetal birth length and weight, and that patients on natalizumab had higher relapse rates during pregnancy and postpartum than control patients with multiple sclerosis who were untreated or used injectable agents.