Predictive factors for flares of established stable systemic lupus erythematosus without anti-phospholipid antibodies during pregnancy.

PURPOSE To identify predictors of systemic lupus erythematosus (SLE) flares during pregnancy in patients previously considered to be at low risk. MATERIALS AND METHODS The retrospective cohort study included 54 singleton pregnancies, managed between 2005 and 2019, involving maternal diagnosed SLE at a low disease activity (SLE Disease Activity Index ≤4) for ≥12 months before conception and without anti-phospholipid antibodies. Pregnancy outcomes were compared between patients who had SLE exacerbations during pregnancy (flare group, n = 21) and patients that did not have a flare (non-flare group, n = 33). RESULTS The flare group had shorter gestational durations (p = .01), lower birth weights (p = .02), and a higher risk of emergent cesarean section (p = .002) compared with the non-flare group. The flare group demonstrated higher doses of prednisone (p = .04) at the time of conception as well as an increased rate of low 50% hemolytic complement (CH50) activity (p = .03) in the first trimester compared to the non-flare group. A decision tree drawn using a prednisone dose ≥10.5 mg/day and a low CH50 predicted SLE flares with a net accuracy of 78%. CONCLUSIONS A prednisone dose ≥10.5 mg daily and CH50 hypocomplementemia in early pregnancy are useful in the early detection of patients at a high risk of SLE exacerbation.