Abnormalities of the fetal heart rhythm: fetal bradyarrhythmias

Yannaeva N.E., Bokeriya E.L.

Academician V.I. Kulakov National Medical Research Centre for Obstetrics, Gynecology and Perinatology, Ministry of Health of Russia, Moscow, Russia

Fetal bradycardia refers to a sustained fetal heart rate less than 110 beats per minute for at least a 10-minute period. There can be different types of bradycardias: sinus, low atrial or nodal bradycardia, blocked atrial bigeminy or atrioventricular (AV) block. 
AV block is the most common type of fetal bradycardia and occurs in 1 in 15,000–20,000 live births. There are 3 degrees of AV block: the first degree, the second-degree type 1 and type 2 and the third (full) degree.
Autoimmune congenital AV block is a passively acquired autoimmune disorder of the conduction system associated with the transplacental transition of maternal autoantibodies to the developing fetus. Clinical signs of fetal AV block of autoimmune origin most often appear in the period from the 18th to the 24th week gestation. First- or second-degree AV block has short reversibility windows, and early detection of this type of rhythm disorder is important for the treatment, since it is possible to stop pathological changes in the myocardium of the fetal heart at this stage of the process. Third-degree AV block is considered irreversible.
The probability of death in newborns with complete AV block ranges from 15 to 30%. The risk of intrauterine death is 6%, and the overall 10-year survival rate is 86%. Dilated cardiomyopathy develops in the neonatal period in 5–30% of cases, and most newborns require the implantation of a permanent artificial pacemaker.
Conclusion: Fetal arrhythmias can be diagnosed with high accuracy and can be managed therapeutically. The examination of all fetuses with an irregular rhythm or a heart rate that does not correspond to the gestational age is justified and may help identify the cause of the disease, affect treatment tactics and further prognosis. As a rule, severe cardiac arrhythmias in the fetus and early gestational period when arrhythmia develops lead to the severe course of the disease in the fetus, high probability of nonimmune fetal hydrops and antenatal fetal death.

Authors’ contributions: Yannaeva N.E. – collecting and processing material, writing the text; Bokeriya E.L. – developing the concept and design of the study, verifying the accuracy of the data and the correct interpretation of medical terms, editing the article.
Conflicts of interest: Authors declare lack of the possible conflicts of interests.
Funding: The study was conducted without sponsorship.
For citation: Yannaeva N.E., Bokeriya E.L. Abnormalities of the fetal heart rhythm:  fetal bradyarrhythmias.
Akusherstvo i Ginekologiya/Obstetrics and Gynecology. 2024; (2): 15-22 (in Russian)


abnormality of the fetal heart rhythm
fetal bradycardia
atrioventricular block
congenital long QT syndrome
AV interval
anti-Ro/SSA antibodies


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Received 17.11.2023

Accepted 20.12.2023

About the Authors

Natalia E. Yannaeva, PhD, Researcher, ultrasound diagnostics doctor, Academician V.I. Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology, Ministry of Health of Russia, +7(495)438-22-92, yannaeva@yandex.ru, 117997, Russia, Moscow, Ac. Oparin str., 4.
Ekaterina L. Bokeriya, Dr. Med. Sci., Professor, I.M. Sechenov First Moscow State Medical University, Ministry of Health of Russia; neonatologist, pediatric cardiologist, Leading Researcher, Academician V.I. Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology, Ministry of Health of Russia, +7(495)438-26-00, e-bockeria@mail.ru, https://orcid.org/0000-0002-8898-9612, 117997, Russia, Moscow, Ac. Oparin str., 4.
Corresponding author: Natalia E. Yannaeva, yannaeva@yandex.ru

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