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CHARLOTTE, NC — Prenatal use of two of the most potent multiple sclerosis (MS) disease modifying therapies, ocrelizumab and ofatumumab, appears safe, with no association with increased risk of adverse pregnancy outcomes, new research showed. 

While databases created to track outcomes are still accumulating data, the study of ocrelizumab with 5095 pregnancies represents “the largest dataset of pregnancy outcomes following exposure to a high-efficacy MS therapy,” said investigator Kristen M. Krysko, MD, an assistant professor of neurology at the University of Toronto, Canada. 

So far, maternal and fetal outcomes have been similar to background rates drawn from epidemiologic data and with outcomes observed in a cohort of women in the database not exposed to ocrelizumab, she added. 

This study, like a similar safety analysis being conducted with ofatumumab, involved real-world data from patients exposed to therapy during pregnancy despite labelling for both drugs that recommends contraception for all women of child-bearing age. The conclusion regarding maternal and fetal safety of ofatumumab was similar.

Both studies were presented May 28 at the Consortium of Multiple Sclerosis Centers (CMSC) 2026 Annual Meeting.

Growing Body of Work 

Previous research reported by Medscape Medical News found that women with MS were significantly less likely to receive high-efficacy drugs or any disease-modifying therapy (DMT) than men, which the lead investigator of that trial attributed to concerns about pregnancy risk.

Earlier studies presented at the 2025 CMSC meeting suggested that the risk of pregnancy complications is low with DMTs, but more longitudinal data on different DMTs was needed. 

The new ocrelizumab study drew on a database started in 2017 and maintained by drug manufacturer Roche. Of 5095 pregnancies in the database, 1309 (median age, 32 years) were prospectively enrolled with a known history of exposure and known outcomes. Relapsing MS was the most common type (67.3%). 

Exposure was defined as ocrelizumab treatment within 3 months of the last menstrual period through pregnancy. Patients who stopped ocrelizumab prior to pregnancy and were therefore not exposed by the study definition, were employed as controls, Krysko reported.

Of exposures, most occurred before the women were aware of their pregnancy. Less than 15% were exposed after the pregnancy was known and the majority of these were in the first trimester. Less than 2% of exposures occurred later in the pregnancy. 

Live birth rates were similar for those with any exposure (87%) relative to those who were not exposed (89.8%). Both were higher than a background epidemiologic rate of under 80%. Among those exposed, there were no remarkable differences between those who receive ocrelizumab prior to detection of pregnancy (85.8%) vs those exposed after the pregnancy was known (89.5%).

The proportion of full-term deliveries and preterm deliveries was similar among groups and rates of major congenital abnormalities were similar or lower (< 3%) across all definitions of ocrelizumab exposure relative to background epidemiologic data. 

Other complications of pregnancy, such as ectopic pregnancies, elective or therapeutic pregnancy terminations, or stillbirths were as uncommon in the drug-exposed patients as in controls or background rates.

“These findings further enhance an informed dialogue on family planning between clinicians and women with MS, balancing safety risks to the infant with the importance of maternal disease control,” researchers noted.

A Look at Ofatumumab 

Using the same definition of exposure, the ofatumumab analysis, called the PRIM study, included data from 906 patients (median age, 31 years). 

Following maternal ofatumumab administration, all outcomes were again “in line with the expected background rates observed in the general population,” reported Riley Bove, MD, an assistant professor of neurology at the University of California, San Francisco. 

Outcomes in this database, maintained by Novartis, are so far available only in about one-third of patients, but all outcomes remain within expected rates and comparable to a cohort of patients exposed to ofatumumab more than 3 months prior to their last menstrual cycle, Bove said.

Most ofatumumab exposures occurred in the first trimester (only 0.3% later). Among cases with known outcomes, 77.6% were live births, 65.6% were full term, and 7.8% were preterm. Other reported rates included ectopic pregnancies (0.9%), spontaneous abortions (14.2%), and major congenital abnormalities (1.7%).

Prevalence of pregnancy outcomes remained within expected range, according to Bove. They were also similar to outcomes in the cohort that stopped ofatumumab prior to pregnancy, a group that represented 11% of the database. 

Data Reassuring, but Not Definitive 

While researchers noted that these data do not provide definitive conclusions about the safety of these two high efficacy therapies in pregnancy, the findings do address a pertinent concern. 

Bove noted that 1 in 3 women with MS conceive following their diagnosis. Krysko, noting that women of child-bearing age are overrepresented in MS populations, agreed that these data in lieu of a controlled trial are relevant. 

Both studies are collecting data globally with major growth in the accrual of cases over the last few years. 

Krysko and Bove cautioned about the limitations of these data, which are not controlled and for which patient follow up is not always complete.

The ocrelizumab study is funded by Roche. The ofatumumab PRIM study is funded by Novartis. Krysko reported financial relationships with Biogen, Bristol-Myers Squibb, EMD Serono, Novartis, Roche, Sanofi, and Touch IME. Bove reported financial relationships with Alexion, Amgen, Cadenza, Eli Lilly, EMD Serono, Novartis, Roche, Sanofi, and TG Therapeutics.