Multiple sclerosis (MS) is the most common disabling neurological disease in young women of childbearing age and has an increasing incidence [1]. Recently Salminen et al. [2] analyzed the outcome of 14 pregnancies of women with MS exposed to glatiramer acetate (GA) treatment during pregnancy, of which nine conceived under GA and continued therapy during pregnancy and the postpartum period. These women were patients with higher MS activity; interestingly, only one patient on continuous treatment with GA experienced two relapses in the postpartum period. The authors concluded that it may be reasonable to continue GA in those patients with previous higher disease activity during pregnancy. The authors did not follow interferon (IFN)-beta exposed pregnancies, the most widely used immunomodulatory drug in MS, mainly due to an FDA C ranking, because of a reduced birth weight observed by Boscovic et al. [3] and a possible increase in abortion rate (largely based on animal data). Actually, GA and IFN-beta are advised to be stopped prior to an anticipated pregnancy, or at the moment when pregnancy is recognized, although IFNs are labeled now to be given during pregnancy after risk–benefit consideration. We present data of pregnancies conceived under IFN and GA and continued IFN or GA during pregnancy and the postpartum period. Out of our nationwide MS and pregnancy database (including now 400 MS pregnancies) we followed seven pregnancies of women with MS (mean age 30.3 years; mean duration of MS 6.5 years) continuing IFN-beta treatment (IFN mothers) throughout pregnancy and postpartum, and three women (mean age 35.7 years; mean duration of MS 9.3 years) continuing GA throughout pregnancy and postpartum (GA mothers). Whilst none of the GA mothers had had a relapse in the year before pregnancy, during pregnancy and in the first 6 months after pregnancy, IFN mothers showed higher disease activity. Four of the IFN mothers had one relapse and two had two relapses in the year before pregnancy. During pregnancy, two relapses in the first trimester of pregnancy occurred, followed by three relapses in the first trimester postpartum and three in the second trimester postpartum, respectively. Birth weight was lower in GA newborns (mean birth weight 3,141.7 g vs. 3,443.6 g IFN newborns), but GA newborns were born earlier [gestational week (gw) 38.3 vs. 39.7]. However, none of these differences caused medical problems. In each group one malformation occurred; one boy whose mother injected IFN-beta 1a throughout pregnancy was born in gw 40 (4,390 g, 52 cm) with a valvular stenosis of the pulmonal artery. The other boy whose mother injected GA until gw 36 ? 2 (2,505 g and 49 cm) was born with penile hypospadia, which will be surgically corrected. All three GA mothers breastfed exclusively during the first 6 months postpartum and none of the children showed noticeable problems, whilst only one IFN mother breastfed exclusively under IFN-beta 1a. Our observational data are the first case series with IFNbeta exposure during the whole period of pregnancy. The higher disease activity in IFN-mothers during and after K. Hellwig received speaker honoraria from Merck Serono, Bayer Schering healthcare, Biogen Idec and Teva Sanofi-Aventis. R. Gold received speaker honoraria from Merck Serono, Bayer Schering healthcare, Biogen Idec and Teva Sanofi-Aventis.