Some people have anti-Ro/SSA antibodies (anti-Sjogren's syndrome-related antigen antibodies). Many people with autoantibodies (also known as anti-Ro antibodies) have autoimmune disorders such as lupus or Sjogren's syndrome, although many do not.

High levels of these antibodies in pregnant women were linked to foetal atrioventricular block (AVB), which occurs when inflammation and subsequent scarring prevent electric signals from the heart's atria from reaching the ventricles. The condition causes life-long pacing and can be deadly.

The study was published in Arthritis & Rheumatology, an official journal of the American College of Rheumatology, and is a peer-reviewed publication for scientists and clinicians interested in the natural history, pathophysiology, therapy, and outcome of rheumatic illnesses.

The magazine publishes high-quality fundamental and clinical research on rheumatic disorders, covering a broad range of topics of investigation.

The incidence of AVB increased with higher levels of anti-Ro/SSA antibodies in the Surveillance To Prevent AV Block Likely to Occur Quickly (STOP BLOQ) trial, reaching 7.7 per cent for those in the top quartile, which increased to 27.3 per cent in those with a previous child who had AVB, though participant numbers in that category were small.

The titers of antibodies did not alter over time. The trial also demonstrated that home-based foetal heart rate monitoring diagnosed conduction problems with high accuracy, potentially reducing the requirement for serial echocardiograms.

"Examining the levels of anti-Ro/SSA antibodies is an important advance since for women with low titers, monitoring is probably not necessary and for those with high titers, the increased risk supports surveillance," said corresponding author Jill Buyon, MD, of NYU Langone Health.

She added that this study also indicated that titers of antibodies do not change and that additional factors besides antibodies contribute to risk.

"That home monitoring can rapidly and accurately identify early foetal conduction disease is a major step forward that may significantly decrease the need for echocardiograms and hopefully facilitate reversibility," added senior author and research professor Bettina Cuneo MD, of the University of Arizona-Tucson College of Medicine.