The importance of the level of maternal anti-Ro/SSA antibodies as a prognostic marker of the development of cardiac neonatal lupus erythematosus a prospective study of 186 antibody-exposed fetuses and infants.

OBJECTIVES: The purpose of this study was to determine whether cardiac complications of neonatal lupus erythematosus (NLE) are related to maternal anti-Ro and anti-La autoantibody-levels.

BACKGROUND: Autoantibody-positive mothers are frequently referred for serial echocardiography because of the elevated fetal risk of developing immune-mediated heart block. Little is known why only some and not all offspring are affected.

METHODS: All cases referred since 2000 for serial fetal echocardiography or cardiac complications related to maternal antibodies were included. Patients without cardiac NLE (group 1) and with cardiac NLE (group 2) were compared. Antibody levels were measured by enzyme-linked immunosorbent assay with a cutoff value of 8 U/ml for a positive test result.

RESULTS: Group 1 included 146 serially screened fetuses with normal pregnancy outcomes. Group 2 consisted of 40 fetuses/neonates with a diagnosis of heart block or endocardial fibroelastosis or both, and included 4 fetuses diagnosed during serial screening. All cardiac complications were associated with moderate (>or=50 U/ml; 15%) or high (>or=100 U/ml; 85%) maternal anti-Ro levels, independently of anti-La antibody titres. The event rate of complete heart block was 5% for prospectively screened fetuses with Ro-values >or=50 U/ml (odds ratio: 7.8) and 0% for fetuses with lower titres (p < 0.0001). Infants with pre-natal exposure to high-titre anti-La levels >or=100 U/ml were the most likely to have noncardiac features of NLE (event rate: 57%; odds ratio: 4.7).

CONCLUSIONS: Our findings support that the amount of maternal antibodies, rather than their presence, is associated with fetal tissue injury. As anti-Ro levels correlate with the risk of cardiac complications, serial echocardiography should be limited to women with high anti-Ro-titres.