What Is an Abnormal Fetal Heart Rate?

Monitoring the fetal heart rate is an essential part of prenatal care, as it provides valuable insights into the baby’s well-being and development. A healthy fetal heart rate indicates that the baby is receiving enough oxygen and nutrients. However, an abnormal fetal heart rate can be a cause for concern and may require further evaluation. In this article, we will explore what constitutes an abnormal fetal heart rate, the potential causes, and the importance of timely medical assessment.

Understanding Fetal Heart Rate

The normal range for a fetal heart rate is typically between 110 and 160 beats per minute. The rate may vary slightly depending on factors such as gestational age, activity levels, and the presence of any underlying medical conditions. Fetal heart rate is commonly monitored during routine prenatal visits using a fetal Doppler or electronic fetal monitoring.

Identifying Abnormal Fetal Heart Rate

An abnormal fetal heart rate is classified into two categories: bradycardia and tachycardia. Bradycardia refers to a heart rate below 110 beats per minute, while tachycardia is defined as a heart rate above 160 beats per minute. Both conditions may warrant further investigation to determine the underlying cause.

Bradycardia

Bradycardia is defined as a condition where the heart beats more slowly than expected, under 110 BPM. This condition is usually temporary. However, in case of persistent bradycardia, such problems as fetal distress or problem with the transmission of electrical signals in the heart may arise. In most cases, fetal bradycardia doesn’t require any treatment. However, there are some cases when interventions are needed, for instance, medication or early delivery.

Tachycardia

Fetal tachycardia is an abnormal or irregular heartbeat known as fetal arrhythmia. It is variably defined as a heart rate above 160-180 BPM. This condition is uncommon and usually temporary. However, when the fetus (developing baby) experiences tachycardia for a long time, it requires urgent treatment. When you are not in labor, you may need to stay in the hospital for monitoring to see how the fetus responds to the medication. There are some cases when babies with tachycardia require follow-up care after they are born.

Cases of abnormal fetal heart rate

Sometimes fetal heart conditions may occur because the fetus is simply moving around. Several factors can contribute to an abnormal fetal heart rate. However, in other cases, it signals a health concern to the baby.  There are maternal factors such as:

• high blood pressure
• anxiety
• gestational diabetes
• anemia
• thyroid problems
• maternal infection
• drug use or nicotine intake.

Fetal factors, such as fetal distress, placental problems, umbilical cord issues, or genetic abnormalities, can also influence the heart rate. Additionally, external factors like maternal stress, dehydration, or certain medications may impact the fetal heart rate.

Monitoring Methods

Early detection and appropriate management can help prevent complications and ensure the best possible outcomes for both mother and baby. There are two ways of checking: external and internal monitoring.

External Monitoring

External monitoring is a commonly used method for checking the fetal heart rate through the mother’s belly. For instance, the fetal heart doppler is an example of external monitoring and can be used during prenatal visits or labor. It involves using a handheld device that emits high-frequency sound waves and detects the reflected waves to assess the baby’s heart rate. It provides real-time information about the baby’s heart rate and allows healthcare providers to assess the heart’s rhythm and detect any abnormalities. Read our article about fetal heartbeat doppler to find out how to use it.

Continuous External Electronic Monitoring

Healthcare providers may also use continuous external electronic monitoring during labor. They secure external sensors to the abdomen with an elastic belt or an electrode that resembles a round sticker. The fetal heart rate and contraction information appear on an attached computer screen. Fetal heart rate monitoring during labor help healthcare providers watch how a fetus responds to contractions, medications, tests, and pushing.

Non-Stress Test (NST)

The non-stress test is a non-invasive method that assesses the baby’s heart rate response to its own movements. It involves using a Doppler ultrasound device or an electronic fetal monitor to measure the baby’s heart rate while the mother is resting or stimulated by gentle movements. The purpose of the NST is to evaluate the baby’s well-being and assess any changes in heart rate patterns during periods of activity and rest.

Internal Monitoring

In some cases, a fetal scalp electrode may be used for direct and continuous monitoring of the baby’s heart rate during labor. It involves placing a small electrode on the baby’s scalp, which can provide more accurate and precise heart rate readings. Fetal scalp electrode monitoring is typically used when there is a need for closer monitoring or when other methods are not providing sufficient information.

Monitoring the fetal heart rate plays a vital role in assessing the well-being of the baby during pregnancy. Understanding what constitutes an abnormal fetal heart rate, its potential causes, and the importance of timely medical assessment is crucial for expectant parents. If you have any concerns about your baby’s heart rate, don’t hesitate to reach out to your healthcare provider. They are equipped to evaluate the situation, provide guidance, and ensure the necessary steps are taken to ensure a healthy pregnancy and delivery.