Background/Purpose: Systemic lupus erythematosus (SLE) affects women of childbearing years and confers an increased risk of pregnancy complications. Risk of adverse events in pregnancy is related to several factors including the presence of autoantibodies, mainly anti-RO60/SSA. There is less known about the associated risk of anti-U1-RNP antibodies in SLE pregnancies. We conducted a retrospective cohort study to evaluate adverse pregnancy outcomes in patients with positive anti-U1-RNP antibodies.

Methods: A retrospective study of patients with 2019 EULAR/ACR SLE and pregnancy data was performed at the Ottawa Hospital. A chart review was conducted for lupus pregnancies documented at our center from 2007 to 2023. We extracted data related to disease manifestations, medications, pregnancy complications (miscarriage, pre-eclampsia, neonatal lupus, congenital heart block, intra-uterine growth restriction/small for gestational age, preterm birth), and autoantibody titers. Descriptives statistics were applied.

Results: We reviewed 212 patient charts and identified 28 patients with documented pregnancy information. 10 of these pregnancies were in patients with positive anti- U1-RNP antibodies. 70% (7/10) of these pregnancies had documented miscarriages which accounted for 48% (10/21) of the documented pregnancy losses in this cohort.  50 % of patients had high titer anti-U1-RNP levels > 644 chemiluminescent units (CU, cut off < 20 CU) and all had titers above 100 CU. Concomitant anti-RO antibody positivity was seen in 60% of patients and 80% were also anti-Smith positive at high titers ( > 694 CU).  Anti-phospholipid antibodies were present in only two patients (20%).  One patient had foetal loss at 8months secondary to pre-eclampsia. Two patients had more than 5 pregnancy losses, while the remainder had 1-2 first trimester miscarriages. All the women had eventual pregnancies to term except for 3 patients, all of which have history of lupus nephritis. 80 % of patients were on hydroxychloroquine for pregnancy but information on low dose aspirin was not always available. In these 10 cases, 7 patients were Black, 1 Asian, 1 first nation and 1 white individual.  Mean age at 1^st pregnancy complication was 31.45 years (SD 6.04).

Conclusion: In this single center cohort, SLE patients with anti-U1-RNP positivity accounted for 48% of the documented pregnancy losses without associated antiphospholipid antibodies. The sample size is small and larger studies are needed to assess the pregnancy risk association with anti-U1-RNP antibodies in SLE. High titer anti-U1-RNP, which has been associated with vascular dysfunction in connective tissue disease, may represent another risk for adverse outcomes as it relates to endothelial adaptions for pregnancy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-u1-rnp-related-pregnancy-loss-in-systemic-lupus-erythematosus/