Rheumatoid arthritis (RA) is a systemic disease, which mainly targets joints and results in osteoarticular destruction and serious disability. When clinical symptoms (painful and swollen joints) occur, the innate and adaptive immune responses against self antigens have already been largely amplified. This might explain that even when RA patients are treated very early and aggressively, a remission of the disease can only be obtained in approximately half of them. This proportion of remission under treatment can only be achieved using treat to target strategies involving biologics, such as anti-TNF. Unfortunately, less than 20% of patients remain in remission after treatment discontinuation. Thus, despite the availability of 5 different types of biologics, there are still therapeutic unmet needs. However, a spontaneous, drug-free decrease of disease activity can be observed in a physiological condition, pregnancy. Although most of treatments of RA have to be discontinued during pregnancy, a marked improvement, and sometimes remission, can be observed during pregnancy, with frequent post-partum flares. The situation is the opposite with an increased risk of flares in systemic lupus erythematosus (SLE), a rare systemic autoimmune disease which generally progresses in flares-up and can affect nearly any organ (the skin, joints, kidneys, the brain, the heart, …). The course of the disease remains unpredictable for a given patient, and very few biomarkers are available to help clinicians to identify patients a risk of flares. Thus, safe therapeutic options remain limited, especially in patients with serious complications. A specific concern in SLE is the fact that the disease usually starts in women entering their sexual and reproductive life. Even with a stable condition (i.e : lupus without recent flares and no impaired renal or cardiac function) as it is medically recommended before getting pregnant, up to 40% of SLE patients flare up during pregnancy.

We hypothesize disease-specific and pregnancy-induced epigenetic changes, especially those regarding the pattern and levels of microRNAs, could explain the clinical improvement and the risk of flares in RA and SLE, respectively. A better understanding of the underlying mechanisms could help to identify new biomarkers, notably those predicting flares in SLE, and therapeutic targets, by trying to mimicking or amplifying micro-RNA changes observed in RA and targeting them in SLE.

Inclusion Criteria:

• ACR criteria for SLE or 2010 ACR criteria for RA
• Absence of any known disease (control group)
• Pregnancy

Exclusion Criteria:

• Age <18
• Other(s) disease(s) that might affect the course of pregnancy (diabetes, uncontrolled hypertension, moderate to severe renal, cardiac or function impairment)

Pregnant women suffering from RA or SLE compared wiht pregnant woman in good health