From the Guidelines
Antepartum prolonged fetal heart rate monitoring is a medical procedure used to assess fetal well-being before labor begins, involving continuous electronic monitoring of the baby's heart rate patterns over an extended period, typically 20-60 minutes, using external devices placed on the mother's abdomen. This monitoring helps healthcare providers evaluate how the fetus responds to its environment and identify potential problems with the placenta or umbilical cord. The primary tools used are electronic fetal monitors with tocodynamometers to detect contractions and ultrasound transducers to capture the fetal heart rate.
Key Components of Antepartum Prolonged Fetal Heart Rate Monitoring
- Normal baseline heart rate (110-160 beats per minute)
- Good variability
- Accelerations with fetal movement
- Absence of concerning decelerations
Indications for Antepartum Prolonged Fetal Heart Rate Monitoring
- Maternal conditions like hypertension or diabetes
- Decreased fetal movement
- Intrauterine growth restriction
- Post-term pregnancy
- Previous pregnancy complications
According to the American College of Radiology 1, antepartum testing is not recommended in low-risk pregnancies, but women with high-risk factors for stillbirth should undergo antenatal fetal surveillance. The strongest evidence supporting antepartum testing pertains to pregnancies complicated by intrauterine fetal growth restriction secondary to uteroplacental insufficiency.
If abnormal patterns are detected, additional testing such as biophysical profiles or delivery might be recommended 1. This non-invasive procedure carries minimal risks and provides valuable information about fetal status, helping clinicians make informed decisions about pregnancy management. The optimal interval of testing is unknown; weekly or twice-weekly testing has become the standard practice in high-risk pregnancies 1.
Umbilical artery Doppler velocimetry is indicated in IUGR secondary to uteroplacental insufficiency 1. The timing for initiation of testing should be tailored on the basis of the risk for stillbirth and likelihood of survival with intervention. Routine antenatal testing cannot predict stillbirth related to acute changes in maternal-fetal status such as those associated with abruption or cord accident 1.
Response to abnormal testing must be individualized on the basis of a number of clinical factors such as gestational age 1. In summary, antepartum prolonged fetal heart rate monitoring is an essential tool for assessing fetal well-being in high-risk pregnancies, and its use should be guided by the latest evidence-based recommendations.
From the Research
Definition of Antepartum Prolonged Fetal Heart Rate Monitoring
- Antepartum prolonged fetal heart rate monitoring refers to the assessment of fetal heart rate (FHR) patterns before labor to evaluate fetal well-being 2.
- The goal of antepartum fetal surveillance, which includes FHR monitoring, is to reduce the risk of stillbirth 2.
- Antepartum fetal surveillance techniques, including FHR monitoring, are used to assess the risk of fetal death in pregnancies complicated by preexisting maternal conditions or those in which complications have developed 2.
Techniques and Indications
- FHR monitoring is used along with real-time ultrasonography and umbilical artery Doppler velocimetry to evaluate fetal well-being 2.
- The biophysical profile score, which includes FHR monitoring, is used to assess fetal well-being and predict fetal acidemia and hypercarbia 3, 4.
- Umbilical artery Doppler velocimetry is also used to identify fetal compromise in high-risk pregnancies and has been shown to decrease perinatal mortality 5.
Clinical Application
- Routine FHR monitoring in the antepartum period has been shown to improve perinatal outcome and may contribute to better resolution of maternal risk classification 6.
- A reactive nonstress test (NST) is defined as 2 accelerations in 10 minutes, with a minimum amplitude of 15 beats/min and a minimum duration of 15 seconds 6.
- Nonreactive NSTs are followed by further testing, such as a stress test, to assess fetal well-being 6.