Most treatments for multiple sclerosis (MS) are not associated with an increased risk of complications during pregnancy, according to a new analysis. A few therapies were associated with slightly elevated rates of congenital abnormalities for babies exposed to treatment during pregnancy, but small sample sizes limit being able to draw firm conclusions about the medications, underscoring a need for future research. Nadine Bast, a pharmacist at St. Josef Hospital in Germany, presented the findings at the American Academy of Neurology (AAN) 2023 Annual Meeting, April 22-27, in Boston and virtually. Her talk was titled, "Pregnancy Outcomes in Multiple Sclerosis patients with or without exposure to Disease Modifying Therapies during pregnancy." More than a dozen disease-modifying treatments (DMTs) are available for relapsing forms of MS. These therapies all broadly work by reducing the activity of the immune system, blunting the inflammatory attack on the brain and spinal cord that drives the disease's symptoms. DMTs can reduce the risk of relapse activity and slow disease progression. MS most commonly manifests in women during childbearing years. There's not much data on using DMTs during pregnancy and if these medicines pose risks to the patient or fetus, however. This means patients often have to make tough choices about treatment during pregnancy without much information to support their decision. The German MS and Pregnancy Registry (DMSKW) was launched in 2006 to collect data through regular telephone interviews on pregnancy outcomes for people with MS in Germany. Bast and colleagues analyzed data from it to assess the impact of DMT use on pregnancy outcomes. The analysis included data from 3,387 pregnancies, of which 2,639 were DMT-exposed, meaning the patient had medication in their system at some point during the pregnancy. The other 748 were unexposed. Exposed to DMTs. Among the DMT-exposed pregnancies, 1,671 were exposed to DMTs such as glatiramer acetate (sold as Copaxone among others), Aubagio (teriflunomide), Tecfidera (dimethyl fumarate), and interferon therapies. These are older medications with less potency for delaying disease progression, but are less likely to cause side effects than newer therapies. The other 968 patients were treated with newer, higher efficacy therapies. These included S1P modulators and CD20 antibodies, as well as Mavenclad (cladribine), Lemtrada (alemtuzumab), and Tysabri (natalizumab). Most patients on S1P modulators were taking Gilenya (fingolimod). The number of patients exposed to any given type of therapy varied widely — there were more than 700 exposed to interferon therapies, compared to less than 20 on Mavenclad, for example. Factors like age at conception and alcohol or tobacco use differed significantly across unexposed groups and compared to the unexposed group. Rates of pregnancy complications such as miscarriage, ectopic pregnancy, and stillbirth were not significantly different between those exposed to any DMT and unexposed patients. There was a higher rate of elective abortions among those treated with S1P modulators, though Bast noted most of these "were for social, not medical reasons," and the rate of elective abortions was very low across groups. Lower birth weights. Regarding outcomes for the baby, rates of chromosomal abnormalities or death shortly after birth were very low and didn't differ between DMT-exposed or unexposed patients. There wasn't a statistically significant difference in rates of major congenital abnormalities between DMT-exposed and unexposed babies. However, Bast noted rates of these abnormalities were higher than 6% among those exposed to Tecfidera, Lemtrada, Mavenclad, or Gilenya, whereas the rate was 3.5% in the unexposed control group. "We have a small sample size here, which limits our statistical power," Bast said, noting future research on DMT use in pregnancy should focus on these medications, as well as S1P modulators besides Gilenya. Babies exposed to Gilenya or Tysabri in pregnancy, particularly those exposed to Tysabri after the first trimester, had significantly lower birth weights than unexposed babies. Newer therapies such as Lemtrada and CD20 antibodies also tended to be associated with lower birth weights. Bast noted these outcomes could be due to an effect of the DMT, but patients given these higher efficacy DMTs might have had more severe underlying disease, which could contribute to the results. All the groups, including unexposed babies, had higher rates of being abnormally small for their gestational age than would be expected in the general population, she said. These findings may help patients faced with decisions about using treatments during pregnancy, Bast said, noting more investigations and international efforts to better understand the potential risks of DMTs in pregnancy are needed. "In order to combine information on rare exposure groups and recently approved medications, we need to harmonize the data collection between international groups to be able to merge the results and get a higher statistical power," she said. Note: The Multiple Sclerosis News Today team is providing coverage of the American Academy of Neurology (AAN) 2023 Annual Meeting April 22-27. 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