Immunological disease activity parameters at conception are risk factors for preterm birth and low birth weight in patients with systemic lupus erythematosus

Objective This study aimed to identify which disease activity parameters may be risk factors for preterm birth (PB) and low birth weight (LBW) in patients with systemic lupus erythematosus (SLE). We also analyzed the extent to which these parameters affected PB and LBW. Methods We collected the SLE Disease Activity Index (SLEDAI), the rate of lupus low disease activity state (LLDAS) attainment, complement levels, and the titer of anti-double stranded DNA (dsDNA) antibody as disease activity parameters. We retrospectively analyzed the associations of these parameters with PB and LBW. Results Sixty pregnancies were included in this study. C3 levels and anti-dsDNA antibody titers at conception were strongly associated with PB (p = 0.03 and p = 0.01, respectively), whereas C3 and CH50 levels were associated with LBW (p = 0.02 and p = 0.03, respectively). A logistic regression analysis showed that the cutoff values of C3 and anti-dsDNA antibody for PB were 62.0 mg/dl and 5.4 IU/ml, respectively. The cutoff values of C3 and CH50 for LBW were 87.0 mg/dl and 41.8 U/ml, respectively. The risk of PB or LBW was increased when divided by the cutoff value, and the combination of these cutoff values showed a significantly higher risk of PB and LBW (p = 0.01 and p < 0.01, respectively). Conclusions PB and LBW are strongly associated with disease activity parameters in patients with SLE. Therefore, strictly monitoring and controlling these disease activity parameters, with or without clinical manifestation, is important for women who want to become mothers.