Prenatal diagnosis of persistent fetal bradycardia: report of four cases.

Persistent fetal bradycardia is infrequent in prenatal life and difficult to manage optimally. It is generally attributable to sinus bradycardia due to fetal distress, blocked atrial extrasystoles, and congenital complete heart block. We reported four cases of persistent fetal bradycardia from 1995 to 1999 in our hospital. The first, second, and third cases of sustained fetal bradycardia had congenital complete heart block with positive titers for anti-Ro/SSA antibodies in both mothers and fetuses. Because of progressive fetal hydrops in the second case, the pregnancy was terminated. The first and third cases were isolated congenital complete heart block without structural anomaly. After prenatal examination the babies were followed up closely until term and both had a good prognosis without any implantation of pacemaker. In the fourth case there was no clinically known etiology associated with sustained fetal bradycardia. The fetal heart rate returned to normal after 6 weeks of follow-up and the baby was delivered without any cardiac problems. Congenital complete heart block is the most common cause of persistent fetal bradycardia. Prenatal detailed monitoring until delivery is necessary before heart failure develops. Treatment strategies (corticosteroids, ritodrine, and plasmapheresis) are debatable and may include prophylactic therapy for high-risk pregnant women.