Use of DMTs in pregnancy on big upswing recently: Study in France

Researchers call for more studies on safety of DMTs for pregnant MS patients

Andrea Lobo, PhD avatar

by Andrea Lobo, PhD |

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Illustration of pregnant woman.

More women with multiple sclerosis (MS) got pregnant in recent years, probably linked to a significantly higher use of disease-modifying therapies (DMTs) during pregnancy, according to a nationwide study in France.

DMTs are a type of treatment that can alter MS course, by reducing the risk of relapses, decreasing disease activity, and/or slowing the accumulation of MS symptoms and disability.

The use of these medications has increased sharply, even though their safety profile during pregnancy is not fully established.

“These findings call for vigilance and for further studies to improve knowledge on the risk profile of these treatments for pregnant women and their exposed children, particularly for the most recent DMTs for which the available information is limited,” researchers wrote.

The study, “Use of multiple sclerosis disease-modifying therapies during pregnancy in France: Nationwide study between 2010 and 2021,” was published in Multiple Sclerosis Journal.

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MS occurs when the immune system mistakenly attacks the myelin sheath, a protective coating around nerve fibers that helps them send electric signals efficiently. The disease is most frequently diagnosed in young adults and in women.

Generally, women with MS are advised to stop DMTs when considering pregnancy, although some medications may be continued during pregnancy if the disease activity necessitates it.

“However, most reports on the use of DMTs during pregnancy focused on specific sub-populations of pregnant women with MS or on specific DMTs, and only few large-scale studies are available,” the researchers wrote. “In addition, to date only few studies have assessed changes in DMT use around the time of pregnancy.”

To know more, a team in France conducted a nationwide study to evaluate use of all available DMTs before, during, and after pregnancy.

The study was performed using the National Mother-Child Register EPI-MERES, built from the French National Health Data System. From April 2010 to December 2021, a total of 20,567 pregnancies occurred in 13,747 women with MS, with a median age at MS diagnosis of 27 years, and a median of four years from diagnosis to the time when patients got pregnant. Some 15.9% of women were pregnant at least three times.

This study highlights a form of normalization of pregnancy in women with MS that has occurred over the last decade with the advent of new DMTs.

From 2010-2012 to 2019-2021, the number of pregnancies increased by 24% in women with MS. This was the result of a 124% rise (from 1,079 to 2,413) in use of DMTs during pregnancy over the same periods, according to the researchers.

A total 7,587 pregnancies (36.9%) were exposed to at least one DMT. Most commonly used medications included interferon-based medications; glatiramer acetate (sold as Copaxone and generics); Tysabri (natalizumab); dimethyl fumarate, available as Tecfidera and generic formulations; Gilenya (fingolimod); and anti-CD20 therapies such as Ocrevus (ocrelizumab).

During pregnancy, women were treated most commonly with a single DMT type (96.6%), and during the first trimester (80.7%).

Moreover, among women on DMTs in the six months before pregnancy, the majority (78%) stopped treatment and 7.6% switched to another DMT generally before or during their first trimester.

Azathioprine and beta-interferon-based medications were discontinued most often, although their discontinuations decreased over time, from 84% in 2010-2012 to 72.4% in 2019-2021.

Switches to a different DMT occurred in an increasing proportion of pregnancies over the same study periods, and were more common in women treated with Gilenya, teriflunomide (available as Aubagio and generic versions), dimethyl fumarate, Tysabri, and anti-CD20 medications. Treatment changes were mostly to glatiramer acetate, beta-interferon, and Tysabri.

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Older pregnant women less likely to discontinue or switch treatments

Pregnant women 35 years or older were 43% less likely to discontinue treatment and 54% less likely to switch to another DMT. Those with lower socioeconomic resources were 74% less likely to discontinue their DMT and 67% less likely to change treatment.

Also, the use of a second-line DMT in the six months before pregnancy decreased the chances of stopping treatment by 29%, while increasing the odds of switching to a different treatment by 77%.

DMTs were mostly resumed within six months (79.1%) after the end of pregnancy, and were generally the same ones used in the six months before the pregnancy.

“In conclusion, this study highlights a form of normalization of pregnancy in women with MS that has occurred over the last decade with the advent of new DMTs. In this context, exposure during pregnancy to treatments whose safety profile has not yet been clearly established has increased sharply,” the researchers wrote.