Low C3 levels, lupus nephritis may predict preterm birth risk in SLE
medwireNews: Low levels of serum complement 3 (C3) protein and a history of lupus nephritis are associated with an increased risk for preterm birth in pregnant women with systemic lupus erythematosus (SLE), Japanese researchers report.
Takuya Kotani (Osaka Medical College) and co-investigators say their “study showed that in pregnancy with SLE, it is important to perform preconception care focusing on organ lesions such as lupus nephritis and serum C3 levels before pregnancy to improve the pregnancy outcome,” even when there is no SLE activity, as determined by a SLEDAI score of 4 or lower.
Kotani and co-authors report in Arthritis Research & Therapy that 83 (76.9%) of the 108 pregnancies they retrospectively reviewed in 74 women with SLE resulted in live births. Of these, 32.5% were preterm births, defined as delivery after 28 weeks’ but earlier than 37 weeks’ gestation (including termination of pregnancy due to hypertensive disorders of pregnancy, preeclampsia, or SLE flare).
The researchers observed no significant differences in age, duration of illness, SLEDAI score, and anti-double-stranded DNA antibody titers between the women who had preterm versus full-term births.
But the women in the preterm birth group had a significantly higher rate of previous lupus nephritis (51.9 vs 14.3%) and a significantly lower median prepregnancy C3 level (77.5 vs 87.5 mg/dL) than those in the full-term birth group.
Area under the receiver operating characteristic curve analysis indicated that a serum C3 cutoff of 85 mg/dL could predict preterm birth with an accuracy of 65%, a sensitivity of 76%, and a specificity of 54%.
On multivariate analysis, women with a C3 level below this cutoff had a significant 4.8-fold higher risk for preterm birth than those with higher prepregnancy C3 levels. In addition, women with a history of lupus nephritis were a significant 6.3 times more likely to experience preterm birth than those with no such history, and the risk increased significantly when these two risk factors were combined.
Specifically, the preterm birth rate was 7.7% among women with no history of lupus nephritis and a C3 level of 85 mg/dL or higher, 39.0% among those with prior lupus nephritis or low C3, and 66.7% among those with both risk factors.
Kotani et al also note that the association between low serum C3 levels remained apparent in the 72 women with no prepregnancy SLE activity (SLEDAI score ≤4). In this subgroup, the preterm birthrate was 29.1% overall, but 42.1% versus 14.7% in women with low versus high C3 levels, respectively, a significant difference.
The investigators point out that a serum C3 level above 85 mg/dL “is higher than the general treatment standard for non-pregnancy (serum C3 levels of 70–75 mg/dL) in SLE patients,” and indicates that “it is necessary to keep the disease activity of pregnant SLE patients more stable than that in non-pregnant patients to avoid preterm birth.”
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