The Clinical Pearl of Fetal Non-Hypoxia Bradycardia

The fetal heart rate is controlled by various integrated physiological mechanisms, most importantly by a balance of parasympathetic and sympathetic nerve impulses. Intrapartum, fetal bradycardia may be in direct response to an evolving or acute hypoxic event, including tachysystole, uterine rupture, or placental abruption. Antepartum, excluding acute events like maternal trauma which could lead to an acute hypoxic episode, most fetal brady arrhythmias will be nonhypoxia related. We recently evaluated and cared for a patient at 23 weeks gestation with the incidental finding during her routine prenatal visit of a fetal HR of 90. This was confirmed by bedside ultrasound, and then noted to be in the 70s on reexamination in L&D. There was no fetal hydrops, no evidence of maternal injury, no maternal connective tissue disease, normal amniotic fluid, and a normal fetal movement seen on ultrasound. What are the possible causes of antepartum fetal bradyarrhythmia? What’s the work-up? What is the fetal Long QT syndrome? And when is delivery recommended? Listen in and find out.