Pregnancy and Multiple Sclerosis

Sadovnick and colleagues¹reported exacerbation numbers and rates in 42 women with multiple sclerosis (MS) during and after 58 pregnancies resulting in live births. They concluded that "neither pregnancy nor the 6-month period after delivery is a risk factor for relapse in MS."¹This conclusion is contrary to clinical experience and to numerous prior reports. Since the results are conflicting, I would appreciate clarification on two issues: the authors' use of the termprospective studyand concerns about the power of their design to detect pregnancy-related differences in exacerbation rates. Sadovnick et al¹state that their data represent the first series of pregnant women with MS who were followed up prospectively, implying, through the use of the termprospective study, that the results are more reliable than those of prior studies. Specifically, they compared their study with a prior work by Birk et al²that reached