In Reply Choudhary and Vinny raised the question about whether a difference in disease-modifying therapies (DMTs) among the women exclusively breastfed compared with those who did not breastfeed exclusively could have introduced bias to the results.1 We thank them for asking this question.
In the original article, there was indeed 1 inconsistency in Table 1: More women who chose not to breastfeed exclusively were treated with DMTs prior to (instead of during) pregnancy (84.2% of the exclusively breastfed group compared with 96.3% of the group that did not exclusively breastfeed; P = .007). Disease-modifying therapies were stopped with the recognition of pregnancy during the first trimester (more commonly in women who chose not to breastfeed exclusively; 36.7% vs 72.8% in the exclusive and nonexclusive breastfeeding groups, respectively; P < .001). It is plausible that the use of DMTs before pregnancy or becoming pregnant while taking DMT was not associated with postpartum relapse risk, as DMTs do not cure multiple sclerosis and their effect would not be expected to last 40 weeks. The large group of women treated with DMTs prior to pregnancy in our study1 might explain that the number of relapses in the 2 years before (in our case mostly while taking DMTs) pregnancy was not significantly associated with postpartum relapses compared with the PRIMS Study,2 as the natural disease activity was masked by the use of DMTs.
Hellwig K, Langer-Gould AM. Breastfeeding and Disease-Modifying Therapy for Multiple Sclerosis—Reply. JAMA Neurol. 2016;73(4):480-481. doi:10.1001/jamaneurol.2015.4821