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About 3 percent of all pregnant women carry an antibody called anti-SSA, or Sjogren’s antibody, which can be detected by a simple blood test. In 4 percent of pregnancies, maternal anti-SSA antibodies cross the placenta at 18 weeks and cause inflammation and fibrosis of the fetal conduction system, resulting in complete atrioventricular block (CAVB) by 25 weeks. Once established, CAVB is irreversible and either death or lifelong cardiac pacing is inevitable.
However, if “emergent” CAVB – the time of irregular rhythm when the fetal heart is transitioning from normal rhythm to CAVB – is detected – transplacental treatment can restore sinus rhythm. To date, surveillance for emergent CAVB has been with weekly fetal echocardiograms, but since emergent CAVB develops in 24 hours, this technique has rarely been successful. An important barrier to progress in this field is the lack of a surveillance method to detect emergent CAVB and prevent progression to irreversible CAVB. Continuous fetal monitoring from 18 to 25 weeks would be the true “gold standard” to detect this fleeting period of emergent CAVB, but this is unrealistic.
Study authors proposed pregnant anti-SSA positive mothers use a commercially available Doppler fetal heart rate monitor* two times per day to detect the irregular rhythm of emergent CAVB (“home monitoring”). All mothers will also undergo standard of care fetal echo surveillance (“office monitoring”) and the two monitoring methods will be compared in the successful detection of emergent CAVB. The multicenter** international observational study, which is still ongoing, is led by Bettina Cuneo, MD, Director of Fetal Cardiology at the Colorado Fetal Care Center and Professor of Pediatrics and Obstetrics at the University of Colorado School of Medicine.
Pregnant anti-SSA positive mothers are recruited at 16-18 weeks of gestation and taught how to use the Doppler fetal heart rate monitor. The mothers are asked to monitor two times per day and to contact their provider if the rhythm is irregular or they cannot hear the baby’s heartbeat. They are seen every other week until 25 weeks of gestation, after which they continue with normal obstetrical care. Participants are also assessed for stress, anxiety and satisfaction with the monitoring.
Decision tree for maternal home FHR Doppler monitoring
* The Cole family provided funding for the monitors in memory of their daughter, Rachel.
**Participating centers include: Sick Kids Hospital, Toronto, Ontario, Canada; Stollery Children’s Hospital, Alberta, Canada; Karolinska University, Stockholm, Sweden; Children’s Hospital Philadelphia; The University of California-San Francisco; Children’s National Hospital, Washington DC; Morgan Stanley Hospital, Columbia, New York; Sanford Health Systems, Fargo, North Dakota
In a pilot study, two mothers with normal office monitoring detected the irregular rhythm of emergent CAVB during home monitoring, which was not detected by echo surveillance. In both fetuses, emergent CAVB developed in less than 24 hours. As part of a larger study, home fetal heart rate monitoring was found to be feasible and empowering to mothers.
One hundred and twenty-five of the 133 (94 percent) recruited anti-SSA positive mothers were enrolled and 120 (96 percent) completed the study. No emergent CAVB or CAVB was missed and all babies were born in sinus rhythm. There was a high rate of acceptance and satisfaction and there was decreased stress with monitoring among the participants. All said they would monitor again in subsequent pregnancies.
Researchers concluded that it is feasible to use a commercially available Doppler monitor to detect arrhythmias and it does not increase stress for participating women. While commercial Dopplers have been available for many years, study authors have found no other instances where they have been used solely for medical indications.
Cuneo BF, Ambrose SE, Tworetzky W. Detection and successful treatment of emergent anti-SSA-mediated fetal atrioventricular block. Am J Obstet Gynecol. 2016;215(4):527-8.
H Cuneo BF, Moon-Grady AJ, Sonesson SE. Heart sounds at home: feasibility of an ambulatory fetal heart rhythm surveillance program for anti-SSA-positive pregnancies (.pdf). J Perinatol. 2017;37(3):226-230.
For more information about the Heart Sounds at Home study, go to clinicaltrials.gov, identifier NCT02920346.