Acute exacerbations may complicate the course of pregnancy and the postpartum period in patients with relapsing-remitting multiple sclerosis (RRMS). To evaluate relapse rate and the effect of immunomodulatory treatment with intravenous immunoglobulin (IVIg) during pregnancy and the postpartum period we retrospectively analysed the data of 108 pregnant RRMS patients. Group I patients were not treated, Group II patients were treated with IVIg 0.4 g/kg body weight/day for 5 consecutive days within the first week after delivery with additional booster doses of 0.4 g/kg body weight/day at 6 and 12 weeks postpartum (defined as 12 weeks after labor), and Group III patients were treated continuously with IVIg during gestation and the postpartum period (0.4 g/kg body weight/day for 5 consecutive days within the 6-8 weeks of gestation with additional booster doses of 0.4 g/kg body weight/day once every 6 weeks until 12 weeks postpartum). All patients underwent antenatal care and fetal ultrasonographic surveillance examinations. Relapse rate per woman per year during the pregnancy and the postpartum period as well as neonatal outcome data and IVIg related adverse events were analysed. Relapse rate per woman per year for patients treated with IVIg for the whole pregnancy and postpartum period (Group III, N = 28) compared with the untreated Group I patients (N = 39) were as follows: first trimester 0.43 vs. 0.72, second trimester 0.15 vs. 0.61, third trimester 0.0 vs. 0.41, and postpartum period 0.28 vs.1.33 (p < 0.05). Patients treated with IVIg only during the postpartum period (Group II, N = 41) also showed a decrease in relapse rate compared with untreated Group I patients, 0.58 vs. 1.33 (p = 0.012). The mean maternal age, disease duration, gestational age at delivery and fetal delivery weight did not significantly differ between the three groups. Mode of delivery, obstetrical complications, the use of epidural analgesia and breast-feeding, did not affect postpartum relapse rate. No severe adverse events were associated with IVIg treatment either during the pregnancy or postpartum period for the patients and newborns.We conclude that in RRMS patients IVIg treatment could be considered as an optional treatment to reduce the incidence of pregnancy and postpartum-related relapses. Further randomized double-blind studies are needed to confirm our findings.