Pregnancy outcomes in female multiple sclerosis patients exposed to intramuscular interferon beta-1a or peginterferon beta-1a reported in a German Patient Support Programme - results from the non-interventional post-authorization safety study PRIMA.

Background: Based on data from two large cohort studies, a label update became applicable for the class of interferon beta therapies in 9/2019, allowing interferons during pregnancy and breastfeeding.

Objective: To assess pregnancy outcomes of women with multiple sclerosis (MS) exposed to peginterferon beta-1a or intramuscular interferon beta-1a therapy (IFN).

Design: Non-interventional post-authorization safety study.

Methods: PRIMA was conducted from April to October 2021 in Germany. Retrospective pregnancy data were retrieved from adult female patients diagnosed with relapsing-remitting MS or clinically isolated syndrome, exposed to IFN before or during pregnancy and registered in the patient support programme (PSP) of the marketing authorization holder's MS Service Centre. The primary endpoint was the outcome of pregnancy. Prospective postpartum data were collected from mothers reporting live births.

Results: In total, 426 women reporting 542 pregnancies between December 2001 and July 2020 (14 pregnancies after the label update) were enrolled. Among patients with confirmed exposure during pregnancy (N = 362), 306 pregnancies (84.5%) resulted in live births (77.6% without defects, 1.9% with defects and 4.4% preterm). Spontaneous abortion, elective termination and stillbirth were reported in 10.9%, 2.8% and 0.2% of the cases, respectively. Higher rates of spontaneous abortions were reported in women with continuous IFN use. A total of 162 women completed the questionnaire for 192 live births within the prospective study part. Mothers restarted IFN therapy or switched to another disease-modifying therapy postpartum in 51.0% and 14.1% of cases, respectively. 158/192 infants (82.3%) were breastfed [34/158 (21.5%)] during IFN therapy. Postpartum relapse activity was low (mothers of 87.3% of breastfed infants remained relapse-free during lactation).

Conclusion: Overall, the prevalence of spontaneous abortions and congenital anomalies of females exposed to IFN exposure before or during pregnancy was within the range reported for the general population. Most mothers paused IFN during pregnancy and breastfeeding. Relapse activity during pregnancy and lactation was observed to be low. These real-world data from a PSP corroborate European and Scandinavian registry data.

Trial registration: NCT04655222, EUPAS38347.