Women with relapsing-remitting multiple sclerosis (RRMS) using moderate- or high-efficacy disease-modifying therapies (DMTs) before conceiving are more likely to have a relapse during pregnancy than are those taking low-efficacy DMTs or no medicines at all, a registry-based study found.
This greater relapse risk during pregnancy could be reduced with careful monitoring, and by having high-efficacy DMT patients continue with their treatment while pregnant.
Study findings were presented at MSVirtual2020 by Wei Yeh, PhD, with Monash University in Australia, in the oral presentation “Pregnancy in a modern day multiple sclerosis cohort: Predictors of relapse during pregnancy.”
However, studies of disease activity in women with RRMS in the context of contemporary treatment options are needed.
Investigators analyzed data covering 1,640 pregnancies in 1,452 women with RRMS, all part of the MSBase Registry, to evaluate their disease activity based on the type of DMT used before conceiving.
“We aimed to compare the characteristics and relapse rates of pregnant women … managed on different classes of DMT before their pregnancies in this modern treatment era,” Yeh said.
Researchers also attempted to identify factors that could be used to estimate the risk of a relapse during pregnancy.
All 1,640 pregnancies in their analysis, including both term and preterm, took place between 2011 and 2019.
Cases were divided into four groups depending on the type of treatment a woman had received the year before conceiving — low-, moderate-, or high-efficacy DMTs, or no DMT.
The frequency of MS relapses — assessed as the annualized relapse rate (ARR) — was calculated for each pregnancy trimester in each group.
Over 845 pregnancies, women were using low-efficacy DMTs the year before conceiving. Interferon-beta was the most commonly prescribed medication in this group, used in 597 of these cases.
Moderate-efficacy DMTs were given to 207 women in the year prior to conception, while high-efficacy DMTs were given to 242 women.
Gilenya (fingolimod) was the most commonly used moderate-efficacy DMT (147 cases), while Tysabri (natalizumab) was most frequently prescribed in the high-efficacy class (219 cases). Over the remaining 346 pregnancies, women were not treated with a DMT.
“In the year prior to conception, the relapse rates were relatively similar between treatment efficacy groups,” Yeh said.
This changed during the pregnancy itself.
Analyses showed that women on either a low-efficacy DMT or no DMT the year before conceiving experienced an ARR drop during pregnancy.
Those on moderate-efficacy DMTs saw their annualized relapse rates rise over the first trimester, and then lower over the third. For those on high-efficacy DMTs, the ARR increased gradually over the entire duration of the pregnancy.
“This is of great interest because it is quite different from what has been demonstrated and described in historical studies,” Yeh said.
After delivery, an increase in relapse activity is seen across all treatment groups, although these values were significantly higher among women on moderate- or high-efficacy DMTs compared with those on low-efficacy DMTs.
Analyses also showed that higher ARR values prior to conception and the use of moderate- or high-efficacy DMTs the year leading up to pregnancy were both associated with a greater relapse risk during pregnancy.
This higher risk of a pregnancy relapse, however, was seen to lower if women continued to take high-efficacy DMTs, such as Tysabri, while pregnant.
“Continuation of high-efficacy DMTs into pregnancy protected against relapse in pregnancy,” Yeh said.
Women age 35 or older at the time of conception were also found to have a lower relapse risk during pregnancy.
Overall, “women with RRMS treated with moderate or high-efficacy DMT are at greater risk of relapse during pregnancy,” the team concluded.
Their findings also suggest that “careful pregnancy management, and use of long-acting high-efficacy DMT preconception, or continuing natalizumab [Tysabri] into pregnancy, may prevent relapse in pregnancy.”
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