No Major Adverse Pregnancy Outcomes With Fetal Exposure to DMTs in Women With MS

Among women with multiple sclerosis (MS), in-utero exposure to disease-modifying therapies (DMTs) is not associated with an increased risk for adverse pregnancy outcomes. These are the findings of a large population-based study published in the Multiple Sclerosis Journal.

Clinicians recommend the discontinuation of all DMTs prior to conception for women with MS who are planning on becoming pregnant, unless the risk for worsening of MS outweighs the risk to the fetus. Current evidence suggests that women with active MS may continue being treated with first-generation, injectable DMTs, such as interferon beta and glatiramer, until conception and even throughout pregnancy, in order to control disease activity. The use of second-generation, high-efficacy DMTs, such as natalizumab, fingolimod, and anti-CD20 antibodies, however, has been linked to a number of adverse pregnancy and neonatal outcomes.

For the study, researchers explored the associations between MS during pregnancy and the risk for perinatal adverse outcomes. Among women with MS, they also explored whether in-utero exposure to DMTs and MS-specific clinical factors were linked to increased adverse risks.  

The researchers evaluated singleton births among mothers with MS and matched mothers without MS from the general population in Sweden. Swedish health care registries (ie, the Swedish MS Register, the National Patient Register, and the Medical Birth Register) were used to identify women with MS in whom onset of the disease had occurred prior to the live birth of their child.

Data from the Prescription Drug Registry and the Swedish MS Register were used to evaluate exposure to DMTs among women with MS within 3 months prior to conception and during their pregnancy.

The study sample comprised 29,568 pregnancies, with 3,418 of these pregnancies among 2,310 women with MS and 26,150 of the pregnancies among women without MS. Overall, 34% (1172 of 3418) of the pregnancies in women with MS had been exposed to a DMT within 3 months (6 months for rituximab) prior to and during their pregnancies.

Compared with women without MS, those with MS were, on average, older at the time of delivery, nulliparous, had a higher level of education, were born in Nordic countries, and smoked or used snuff during their pregnancies.

Maternal MS during pregnancy, compared with pregnancies among women without MS, was linked to a higher risk for cesarean delivery, instrumental delivery, maternal infection, and antepartum hemorrhage/placental abruption. Further, compared with the neonates of women without MS, those of women with MS had significantly higher risks for medically indicated preterm birth (ie, <37 weeks), early term birth, and being born small for gestational age. Exposure to DMTs was not related to any increased risks for malformations.

The researchers noted there are several limitations of the study that warrant mention. The Prescription Drug Register used in the analysis provides information only on those drugs that have been dispensed from pharmacies, with any information on medication compliance not being captured. ADMTs given via infusion, however, including natalizumab and rituximab, are administered in the clinic, with each infusion documented in the Swedish MS Register. Data completeness for DMTs recorded in the Swedish MS Register is high in comparison with those noted in medical chart reviews.

“Overall, the absolute risks for adverse outcomes were small and should not influence the MS patient’s family planning but raise awareness in health care providers monitoring pregnancies in women with MS,” the researchers concluded.

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.