At what gestational age should Doppler heart rate monitoring start during antepartum visits?

From the Guidelines

Doppler heart rate monitoring should start at 16 weeks of gestation for high-risk pregnancies, such as those with suspected fetal growth restriction (FGR), and at 28 weeks for low-risk pregnancies, as part of routine antepartum visits. The American Journal of Obstetrics and Gynecology recommends serial umbilical artery Doppler assessment to assess for deterioration once FGR is diagnosed 1. According to the Society for Maternal-Fetal Medicine, Doppler assessment of the umbilical artery is recommended for pregnancies with FGR, with the frequency of assessment depending on the severity of the FGR and the presence of abnormal Doppler findings 1.

Key Considerations

• The decision to start Doppler heart rate monitoring is based on the individual patient's risk factors and medical history.
• For high-risk pregnancies, such as those with suspected FGR, Doppler monitoring should start earlier, at around 16 weeks of gestation.
• For low-risk pregnancies, Doppler monitoring can start at 28 weeks of gestation.
• The frequency of Doppler assessments should be individualized based on the patient's specific condition and the presence of abnormal Doppler findings.

Recommendations

• Start Doppler heart rate monitoring at 16 weeks of gestation for high-risk pregnancies.
• Start Doppler heart rate monitoring at 28 weeks of gestation for low-risk pregnancies.
• Perform serial umbilical artery Doppler assessments to assess for deterioration once FGR is diagnosed.
• Individualize the frequency of Doppler assessments based on the patient's specific condition and the presence of abnormal Doppler findings, as recommended by the Society for Maternal-Fetal Medicine 1.

From the Research

Doppler Heart Rate Monitoring in Antepartum Visits

• The optimal gestational age to start Doppler heart rate monitoring during antepartum visits is not explicitly stated in the provided studies.
• However, study 2 suggests that fetal heart rate characteristics can be defined between 25-28 weeks' gestation, which may imply that Doppler heart rate monitoring could start around this period.
• Study 3 evaluates the longitudinal pattern of fetal heart rate short-term variation and Doppler indices in severe growth-restricted fetuses, but does not provide a specific gestational age for starting Doppler heart rate monitoring.
• Study 4 examines the effect of antenatal betamethasone administration on fetal biophysical activities and Doppler flow indices, but does not address the timing of Doppler heart rate monitoring.
• Study 5 discusses fetal pulse oximetry for fetal assessment in labor, but does not provide information on the timing of Doppler heart rate monitoring in antepartum visits.

Key Findings

• Study 2 found that reducing the acceleration amplitude criteria to 10 bpm in preterm pregnancies maximizes the number of reactive nonstress tests.
• Study 3 showed that fetal heart rate short-term variation does not deteriorate continuously, and Doppler indices of umbilical and middle cerebral arteries deteriorate starting about three weeks prior to delivery.
• Study 4 found that betamethasone induces a profound, albeit transient, suppression of fetal breathing, limb, and trunk movements.
• Study 5 found that the addition of fetal pulse oximetry does not reduce overall caesarean section rates, but may reduce caesarean section for nonreassuring fetal status when used in the presence of a nonreassuring CTG.

Limitations

• The provided studies do not directly address the question of when to start Doppler heart rate monitoring during antepartum visits.
• The studies focus on different aspects of fetal monitoring, such as fetal heart rate characteristics, biophysical activities, and Doppler flow indices.