Overview
Fetal bradycardia refers to an abnormally low fetal heart rate, typically below 110 beats per minute, which can indicate various underlying conditions affecting fetal well-being 13.Diagnosis
Key Diagnostic Criteria: FHR below 110 bpm 13.
Recommended Tests:
- Doppler ultrasound assessment of umbilical artery impedance indices and half peak systolic velocity (h-PSV) deceleration time 1.
- Monitoring for associated changes in fetal oxygenation and uterine blood flow 2.
Grading: Use nomograms for h-PSV deceleration time to assess placental vascular resistance 1.Management
First-Line Treatments:
- Address underlying causes such as placental insufficiency or maternal factors 12.
- Ensure adequate oxygenation and ventilation support if fetal hypoxia is suspected 2.
Adjunctive Treatments:
- Specific drug dosing not detailed; focus on supportive care and monitoring 12.Special Populations
Pregnancy: Fetal bradycardia may be associated with placental dysfunction; monitoring umbilical artery Doppler parameters is crucial 1.
Comorbidities: Local anesthetic use (e.g., paracervical block) can induce fetal bradycardia via potential hypoxia mechanisms 2.Key Recommendations
Utilize h-PSV deceleration time nomograms for assessing placental vascular resistance in fetuses with bradycardia (Evidence: Moderate) 1.
Consider fetal hypoxia as a potential cause of bradycardia following procedures like paracervical block anesthesia (Evidence: Moderate) 2.
Recognize that inappropriate fetal bradycardia responses may occur due to intrauterine stress mechanisms (Evidence: Expert opinion) 3.References
1 Bustos JC, Paublo M, Ramirez P, Sepulveda W. Umbilical artery half peak systolic velocity deceleration time throughout pregnancy and its role in fetuses with bradycardia. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2007. link
2 Morishima HO, Covino BG, Yeh MN, Stark RI, James LS. Bradycardia in the fetal baboon following paracervical block anesthesia. American journal of obstetrics and gynecology 1981. link90739-0)
3 Goodlin RC. Inappropriate fetal bradycardia. Obstetrics and gynecology 1976. link