Incidence of pregnancy and disease-modifying therapy exposure trends in women with multiple sclerosis: A contemporary cohort study

Background: Exposure to disease-modifying therapy (DMT) during early pregnancy in women with relapsing-remitting MS (RRMS) may be increasing. Objective: To retrospectively determine incidence of pregnancy, DMT exposure and pregnancy outcomes in women with RRMS. Methods: We identified all women with RRMS aged 15–45 years in the MSBase Registry between 2005–2016. Annualised pregnancy incidence rates were calculated using Poisson regression models. DMT exposures and pregnancy outcomes were assessed. Results: Of 9,098 women meeting inclusion criteria, 1,178 (13%) women recorded 1,521 pregnancies. The annualised incidence rate of pregnancy was 0.042 (95% CI 0.040, 0.045). A total of 635 (42%) reported pregnancies were conceived on DMT, increasing from 27% in 2006 to 62% in 2016. The median duration of DMT exposure during pregnancy was 30 days (IQR: 9, 50). There were a higher number of induced abortions on FDA pregnancy class C/D drugs compared with pregnancy class B and no DMT (p = 0.010); but no differences in spontaneous abortions, term or preterm births. Conclusions: We report low pregnancy incidence rates, with increasing number of pregnancies conceived on DMT over the past 12-years. The median duration of DMT exposure in pregnancy was relatively short at one month.