Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, predominantly affecting women of childbearing age. Therefore, issues of conception, pregnancy, and delivery are of significant importance to patients and treating physicians. We discuss immunologic and clinical effects of pregnancy on the course of MS including both immunosuppression on a local level and a heightened state of immunocompetence on a global level. Clinical outcomes of the Pregnancy in Multiple Sclerosis trials are reported. We analyze and update the available data on safety and efficacy of immunomodulating MS treatments and symptomatic treatments for pregnant and lactating women, and address specific issues of MS management at the time of pregnancy. We review the data related to estrogen-based MS therapies currently or previously in trials. Pregnancy does not appear to be associated with adverse outcomes in MS patients. Some evidence suggests possible beneficial effects, although clear prospective data of sufficient length and quality are limited. Long-term relapse rates or disability progression do not seem to be affected by pregnancy in MS patients. The use of immunosuppressive or immunomodulatory agents in pregnancy is not routinely advisable but could be considered under special circumstances.