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.