Little is known about the influence of immunomodulation on parenthood, in particular paternity in multiple sclerosis (MS). The objective was to determine whether there is an increased risk for pregnancies initiated by MS-parents under disease modifying therapies (DMT). We investigated the clinical outcome of pregnancies fathered by MS-patients under DMT by nationwide questionnaire and within our own outpatient clinic. Additionally, we compared the birth weight of children from MS-fathers exposed to DMT, MS-mothers without DMT, MS-mothers under interferon-beta (IFN beta) at the time of conception and healthy controls (HCs). DMT was reported for 32 paternities of 46 children; 30 under IFN beta, 12 under glatiramer acetate, 2 under natalizumab, 1 under methotrexate and 1 under combined azathioprine- and IFN beta-1b-treatment. Six (13%) pregnancies ended in early spontaneous abortions; of the 40 children of MS-fathers under DMT, 2 (5%) were preterm, 1 (2.5%) had a spinal lipoma and 3 (7.5%) had moderate hip dysplasia, of whom 2 were siblings whose mother had severe hip dysplasia. Mean birth weight of newborns from MS-fathers under DMT was not significantly reduced compared to HCs. Comparing birth weight of newborns of MS-mothers versus MS-fathers, we found a significant difference to the disadvantage of MS-mothers with or without IFN beta-treatment. No statistical difference in birth weight of IFN beta-exposed versus untreated MS-mothers was observed. Despite the small numbers, our available data suggest safe paternity by MS-patients. IFN beta-treatment of mothers does not seem to have an impact on birth weight, however, MS may contribute to a reduced birth weight.