During pregnancy, alterations take place in mother's immune system with the goal of maintaining a successful pregnancy, and delivering healthy offspring. Immune alterations include activation of the innate immune system and dampening of cell-mediated adaptive immunity. Due to these alterations, cell-mediated autoimmune diseases typically ameliorate during pregnancy. The objectives of this study were to evaluate whether C-reactive protein (CRP) concentration, a sensitive marker of systemic inflammation (1) is increased during MS pregnancy (2) predicts pregnancy-related co-morbidities associated with MS (3) predicts MS disease activity after delivery. CRP concentration was measured using a high sensitivity assay from seven prospectively collected serum samples of 41 MS patients and 19 controls during pregnancy and 6 months after delivery. Annualized relapse rates, EDSS, fatigue scores and obstetric details of the patients were recorded. Delivery-related CRP levels were significantly elevated both among MS patients and in controls. CRP levels were higher during pregnancy than during the postpartum period in both study groups. Delivery-related elevated CRP levels did not correlate with postpartum disease activity. MS patients with eventual gestational diabetes had a significantly higher median CRP in the beginning of pregnancy compared to non-diabetic MS patients (9.28 vs. 2.98 mg/l, p = 0.0025). MS patients reporting fatigue had a significantly higher CRP throughout pregnancy compared to patients without fatigue. Higher CRP values were associated with pregnancy-related co-morbidities but not with MS disease activity.