Understanding heart block in developing babies and treatment outcomes

The Slow Heart Registry is an international study that follows pregnant people whose babies are diagnosed with a severe heart rhythm problem called immune-mediated heart block. Researchers want to learn how different prenatal treatments — particularly fluorinated glucocorticoids (a type of steroid) — affect outcomes for these babies. By gathering information from hospitals around the world, the study aims to understand which care approaches help babies survive and thrive.

Immune-mediated fetal heart block is a rare but serious condition, and doctors are not yet certain which prenatal treatments work best. This study was created to gather real-world information about how babies with this condition are currently being cared for and how they do over time, so that future pregnant people and their doctors can make better-informed decisions.