Change in pregnancy-associated multiple sclerosis relapse rates over time: a meta-analysis.

BACKGROUND

Women with MS are advised that relapse rates fall during pregnancy and rebound post-partum. This advice originates from 1998; smaller, more recent, studies have not been previously pooled.

METHODS

All studies published since 1998 providing raw relapse data were considered for inclusion. Single arm meta-analysis was performed using a restricted maximum likelihood random effects model with inverse variance; secondary subgroup analysis and meta regression were then performed. Annualised relapse rates (ARR), or relapse numbers/rates suitable for conversion into ARR during pregnancy and the post-partum period were included. Secondary subgroup analysis examined year of data collection, DMT exposure, breastfeeding and data source.

RESULTS

7034 pregnancies from 6430 women were included. ARR fell from 0.57 (95%CI 0.45-0.70) pre-pregnancy to 0.36 (0.28-0.44), 0.29 (0.21-0.36) and 0.16 (0.11-0.21) during trimesters 1,2, and 3, with a post-partum rebound (ARR 0.85, 95%CI 0.70-1.00). ARR reduced pre-pregnancy and post-partum over time (p<0.001). Relapse rates were lower in claims databases than elsewhere.

CONCLUSIONS

Despite high heterogeneity, we confirm the historic assumption that ARR reduces during pregnancy, and demonstrate an overall reduction in ARR over time. Studies using data originating from claims databases demonstrated a lower relapse rate at all time points, which has not previously been demonstrated.