Background: Pregnancy is considered to influence the disease course in women with multiple sclerosis (MS).

Objective: The aim of this study was to investigate the effect of pregnancy on long-term disability accrual in women with MS.

Methods: The Danish Multiple Sclerosis Registry (DMSR) was used to identify women diagnosed with clinically isolated syndrome or relapsing-remitting MS. Cox models with pregnancy as a time-dependent exposure and propensity score (PS) models were used to evaluate time to reach confirmed Expanded Disability Status Scale (EDSS) score of 4 and 6.

Results: A total of 425 women became parous and 840 remained nulliparous. When including pregnancy as a time-dependent exposure, a non-significant association with time to reach EDSS 4 (hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.61-1.20) and EDSS 6 (HR 0.70, 95% CI 0.40-1.20) was found. Correspondingly, the PS model showed no association with pregnancy on time to reach EDSS 4 (HR 0.85, 95% CI 0.56-1.28).

Conclusion: This study concludes that pregnancy does not affect long-term disability accumulation.