Fetal heart rate (FHR) monitoring is used throughout pregnancy and labor to assess the baby’s well-being. The heart rate indicates whether the fetus is receiving adequate oxygen supply. A normal FHR typically ranges between 110 and 160 beats per minute (bpm) for most of the pregnancy. This rate naturally fluctuates as the baby responds to its environment. This article discusses temporary fluctuations, but any sustained or concerning changes must be assessed by a healthcare provider immediately.
Factors That Temporarily Elevate Fetal Heart Rate
A temporary increase in FHR is often a normal physiological response, similar to an adult’s heart rate increasing during activity. The most common reason is fetal movement or stimulation, where the heart rate accelerates as a sign of well-being and neurological responsiveness. This temporary spike, known as a reactive acceleration, demonstrates the baby is active and receiving sufficient oxygen.
Maternal physiological states also directly influence the fetal heart rate. Moderate-to-intense physical activity increases maternal heart rate and metabolism, leading to a corresponding, temporary rise in the baby’s heart rate. Maternal stress or anxiety can also elevate FHR due to the passage of stress hormones, such as cortisol, across the placenta.
Maternal illness, especially fever or infection, frequently causes FHR elevation, often resulting in fetal sinus tachycardia. Increased maternal body temperature causes the fetal heart to beat faster to regulate its own temperature. Dehydration can also lead to elevated FHR because reduced maternal fluid volume decreases blood flow to the uterus, prompting compensation.
Certain medications taken by the pregnant person can act as stimulants, causing a temporary rise in FHR. Over-the-counter decongestants (like pseudoephedrine or phenylephrine) and some asthma medications have sympathomimetic effects that increase heart rate. If concerned about any medication, discuss its potential effects on the baby with a healthcare professional.
Immediate Non-Medical Strategies for Stabilization
When an elevated FHR is noted, several immediate, non-medical steps can optimize the fetal environment and encourage stabilization. The primary strategy is a change in maternal position. Lying on the left side is recommended because it relieves pressure from the uterus on the vena cava. This maneuver, called left lateral positioning, immediately improves maternal cardiac output, increasing blood flow and oxygen delivery to the fetus.
Another rapid intervention involves maternal hydration, which addresses the common factor of dehydration. Drinking a large glass of water or other clear fluids quickly increases the mother’s circulating blood volume. This improved fluid status helps lower the baseline FHR by improving placental perfusion.
Reducing maternal stress and promoting rest helps stabilize a temporarily elevated FHR. Relaxation techniques, such as deep breathing or sitting quietly, lower the mother’s heart rate and circulating stress hormones. Since maternal stress hormones cross the placenta, calming the maternal nervous system benefits the fetal heart rate.
If the mother is overheated, removing extra layers of clothing or using a cool compress can help reduce the maternal temperature. This addresses a common cause of fetal sinus tachycardia. These actions optimize conditions, but communication with a medical professional is necessary if the elevation is sustained.
Distinguishing Temporary Increases from Fetal Tachycardia
The distinction between a normal, temporary spike in FHR and true fetal tachycardia lies in the degree and duration of the elevation. A temporary increase (acceleration) is usually brief and signals a healthy, reactive fetus. Fetal tachycardia is defined as a sustained heart rate above 160 bpm for 10 minutes or longer. This sustained high rate indicates the baby’s system is compensating for an issue, such as infection, fever, or reduced oxygen.
Fetal tachycardia accompanied by other warning signs requires immediate professional medical attention. Symptoms of concern include a noticeable decrease or absence of the baby’s movement, vaginal bleeding, or intense abdominal pain or cramping. These combined signs suggest the elevated heart rate may be a response to fetal distress rather than a benign fluctuation.
Upon reporting a sustained high heart rate, a healthcare provider typically initiates a medical assessment. This often involves a Non-Stress Test (NST) or a Biophysical Profile (BPP) to evaluate the baby’s heart rate, movement, tone, and breathing. The goal is to determine if the high rate is a non-concerning response or a sign of an underlying issue. If a sustained FHR above 160 bpm is noted for 10 minutes or more, or if accompanied by worrying symptoms, seek medical attention immediately.