Abstract Body (Do not enter title and authors here): Introduction:
Fetal cardiac neonatal lupus (CNL) due to maternal anti-Ro antibodies (anti-Ro Ab) manifests as atrioventricular block (AVB) and/or extranodal cardiac disease. Despite the high morbidity and mortality, surveillance to detect fetal CNL before it is irreversible is variable. Because of diverse surveillance practices and no routine prenatal screening for anti-Ro Ab, we aimed to compare the diagnosis (dx) and management of fetal CNL between pregnant patients (pts) with and without pre-pregnancy knowledge of anti-Ro Ab.

Methods:
This was a retrospective multicenter cohort study of fetuses diagnosed between January 2013-January 2024 in 22 centers from the Fetal Heart Society Research Collaborative. Fetal CNL was defined as confirmed anti-Ro Ab and AVB or extranodal disease (cardiomyopathy, valvulitis, hydrops and/or endocardial fibroelastosis). Categorical data are presented as frequency (%). P-values are from the Fisher’s exact test for categorical outcomes. All analyses completed in R v4.2.2.

Results:
There were 233 fetal pts with CNL from 231 pregnancies. Over half (57%) of pregnant pts were unaware of anti-Ro Ab at CNL dx. Pregnant pts with known anti-Ro Ab were diagnosed with CNL earlier by 1.5 weeks (p=0.002). Of those with known anti-Ro Ab, 14 (14%) had at least one prior child with CNL, yet only 8 (57%) received hydroxychloroquine prophylaxis in the 1^st trimester. CNL surveillance with known anti-Ro Ab consisted of weekly or every other week fetal echocardiograms (47%) and/or ambulatory fetal heart rate monitoring (FHRM) (11%). There was a difference in type of CNL dx when comparing groupings of surveillance and known anti-Ro Ab (p= 0.019), Table 1. Those surveilled (echo and/or FHRM) with known anti-Ro Ab were more likely to have isolated extranodal disease or 1° AVB at CNL dx. Second degree AVB was more commonly identified with FHRM.

Conclusion:
Anti-Ro Ab are more likely to be identified only after a fetal CNL dx. Less than half of pregnant pts with known Anti-Ro Ab had echocardiographic surveillance and less than 60% with prior CNL received the recommended prophylaxis for recurrence. Knowledge of Anti-Ro Ab allowed for earlier dx and surveillance identified lower degrees of AVB or isolated extranodal disease at dx. Further studies are needed to determine if earlier dx and treatment results in better perinatal outcomes. If so, universal Anti-Ro Ab screening in pregnancy and prophylaxis for recurrent CNL should be strongly considered.