Home Monitoring for Fetal Heart Rhythm During Anti-Ro Pregnancies

Background: Fetal atrioventricular block (AVB) occurs in 2% to 4% of anti-Ro antibody–positive pregnancies and can develop in <24 h. Only rarely has standard fetal heart rate surveillance detected AVB in time for effective treatment. Objectives: Outcome of anti-Ro pregnancies was surveilled with twice-daily home fetal heart rate and rhythm monitoring (FHRM) and surveillance echocardiography. Methods: Anti-Ro pregnant women were recruited from 16 international centers in a prospective observational study. Between 18 and 26 weeks’ gestation, mothers checked FHRM twice daily with a commercially available Doppler monitor and underwent weekly or biweekly surveillance fetal echocardiograms. If FHRM was abnormal, a diagnostic echocardiogram was performed. Cardiac cycle length and atrioventricular interval were measured, and cardiac function was assessed on all echocardiograms. After 26 weeks, home FHRM and echocardiograms were discontinued, and mothers were monitored during routine obstetrical visits. Postnatal electrocardiograms were performed. Results: Most mothers (273 of 315, 87%) completed the monitoring protocol, generating 1,752 fetal echocardiograms. Abnormal FHRM was detected in 21 mothers (6.7%) who sought medical attention >12 h (n = 7), 3 to 12 h (n = 9), or <3 h (n = 5) after abnormal FHRM. Eighteen fetuses had benign rhythms, and 3 had second- or third-degree AVB. Treatment of second-degree AVB <12 h after abnormal FHRM restored sinus rhythm. Four fetuses had first-degree AVB diagnosed by echocardiography; none progressed to second-degree AVB. No AVB was missed by home FHRM or developed after FHRM. Conclusions: Home FHRM confirms the rapid progression of normal rhythm to AVB and can define a window of time for successful therapy.