Use of polynomial reference ranges for atrioventricular intervals assessed by fetal echocardiography in anti-Ro/SSA antibody positive pregnancies to exclude fetal heart blocks - a pilot study.

Introduction Maternal anti-Ro/SSA antibodies can cause fetal atrioventricular blocks (AVB). This pilot study aims to apply previously published echocardiographic reference ranges of the fetal AV intervals in the setting of anti-Ro/SSA antibody positive pregnancies in order to exclude a 1° AVB. Materials and Methods Between January 2018 and September 2022 we included all women with known anti-Ro/SSA antibodies followed up at the prenatal ultrasound department of the University Hospital of Bern. AV intervals were serially measured by two previously reported methods and plotted against previously created reference ranges. Results We included 23 pregnancies from 17 anti-Ro/SSA antibody positive women with connective tissue diseases. 443 AV interval measurements were recorded between 16+3 and 38+4 weeks of gestation. 14 (3.2%) AV-intervals measured >150ms, none measured >170ms and 8 (1.8%) were found to be >95th percentile. In none of the pregnancies serial AV-prolongations were noted. The postnatal ECGs demonstrated normal sinus rhythm without AVB in all children. Conclusion AV intervals of pregnancies followed up for anti-Ro/SSA antibodies without neonatal AVB lie within our published polynomial reference ranges. While diagnosing a 1° AVB remains controversial, more data are needed to prove that our reference ranges are helpful to exclude a 1° AVB.