Multiple Sclerosis (MS) is most prevalent among women of childbearing age. The post-partum (PP) period is a critical phase in MS patients, during which a recrudescence of disease activity is expected. Different strategies have been assessed in the prevention of post-partum relapse. High dose methylprednisolone was evaluated in a case control study with historical controls but the positive results have not been confirmed.

In this study, the main objective will be to compare the risk of relapse in the 6 months PP period between patients treated systematically by high dose methylprednisolone after delivery compared to patients who didn't receive a systematic treatment.

The second objective will be focused on the comparison of the disease activity and disability progression in patients who have resumed early a Disease Modifying Drug (DMD) after delivery vs patients who haven't.

Even if two small case control studies underlined the positive effect of high dose methylprednisolone on the relapse risk in the PP period in MS, these data have to be confirmed by a larger study. The impact of such a strategy remains also uncertain concerning the risk of long term disability. In this project, the investigators will also analyze the influence of the delay of DMD reintroduction after delivery on the relapse risk but also on the risk of disability. The results will have an important role in the therapeutic management of the post-partum period in MS patients.

Inclusion Criteria:

• Relapsing MS patients according to MacDonald criteria 2010
• Age between 15 and 49 years old at the pregnancy
• Age between 18 and 51 years old when filling the questionnaire of the study
• At least one full pregnancy with live birth after the beginning of the MS diagnosis
• At least one neurological visit during the 12 months period after the delivery
• At least one neurological visit per year in the 12 months preceding the pregnancy
• Pregnancy must occur between 01/2007 and 01/2017 In case of several pregnancies per woman, only the first one occurring in the period will be analyzed
• Having received information on the protocol and not having expressed opposition to participating in the study.

Exclusion Criteria:

• Patients who have received Immunoglobulines or plasma exchanges after the delivery in prevention of a relapse
• Patients presenting a SPMS or PPMS form at the beginning of pregnancy
• Protected persons referred to in Articles L. 1121-6 to L. 1121-9 of the code of public health (eg minors, persons deprived of liberty, ..) except nursing mothers postpartum.

Study of Preventive use of COrticosteroids during the Post-Partum

relapsing MS patients with at least one full pregnancy with live birth between 01/2007 and 01/2017 after the beginning of the MS diagnosis