Intrapartum fetal heart rate monitoring: Clinical sciences

Chapters:

Watch video only

Introduction0:00–1:00

Intrapartum monitoring of the FH R or fetal heart rate is performed to evaluate fetal heart rate patterns, assess fetal wellbeing and guide interventions during labor.
The basis for monitoring is that the fetal brain modulates cardiac activity through sympathetic and parasympathetic effects, which are influenced by oxygenation status and acid base balance.
The fetal heart rate demonstrates predictable patterns in response to intrapartum events such as fetal sleep, maternal medications, compression of the umbilical cord hypoxia and acidemia.
Two methods of fetal heart rate monitoring are E FM or electronic fetal monitoring and intermittent auscultation em can be performed externally or internally while intermittent auscultation involves periodic listening to the fetal heart rate using a Doppler device or fetal stethoscope on the maternal abdomen.

Focused H&P1:00–2:06

Now, when a patient presents for evaluation and intrapartum fetal heart rate monitoring, your first step is to obtain a focused history and physical examination factors to consider in your patient's history include gestational age, amniotic membrane status and medications.
The patient is receiving such as Oxytocin IV opioids like butorphanol or an epidural on physical exam. Note your patients vital signs and keep in mind that abnormalities in maternal BP, temperature and oxygenation can cause significant fetal heart rate changes, also perform a sterile vaginal exam to check cervical dilation.
Your next step is to assess for high risk conditions including hypertension or diabetes. If there are no high risk conditions, you can monitor with either intermittent fetal auscultation or with continuous electronic fetal monitoring.
However, if a high risk condition is present or if continuous monitoring is preferred by your patient. Perform continuous electronic fetal monitoring.

Apply monitors2:06–6:46

Next, apply the monitors to the patient and assess the fetal heart rate and uterine contraction patterns. The fetal heart rate pattern is described by the baseline variability and presence of accelerations or decelerations.
Additionally, a sinusoidal pattern is an uncommon but important finding. Now, the baseline is the average fetal heart rate rounded to increments of five BPM during a 10 minute segment.
A normal baseline is between 110 and 160 BPM. Tachycardia is above 160 bradycardia is below 110.
Next is variability or the normal fluctuation of the baseline fetal heart rate. Its a result of the fetal heart rate modulation by the parasympathetic and sympathetic nervous systems and is irregular in both amplitude and frequency variability can be absent with no fluctuation, minimal with detectable fluctuations, five beats in amplitude or less moderate with fluctuations between six and 25 beats in amplitude and marked with an amplitude greater than 25 beats in amplitude.
From baseline, persistently absent. Variability is concerning for fetal acidemia but can be normal in fetuses, less than 28 weeks of gestation.
Minimal variability can occur with the fetal sleep cycle or with medications like intravenous opioids or magnesium sulfate.
Moderate variability usually indicates a well oxygenated fetus and marked variability is usually a benign finding which could be associated with an increase in alpha adrenergic activity.
Next, accelerations are abrupt transient increases in the fetal heart rate above the baseline for at least 15 BPM with a duration of at least 15 seconds.
Accelerations are a reassuring sign and reflect normal fetal acid base status and are usually associated with fetal movement.
Decelerations are decreases in the fetal heart rate and are categorized by the relationship with uterine contractions. Early decelerations have a gradual symmetric decrease and return to baseline that mirror the timing of a contraction.
They start at the onset of a contraction nader at the peak of the contraction and recover at the end of the contraction.
Early decelerations represent a fetal vagal response to head compression during descent. In the pelvis.
They are benign and do not reflect abnormal fetal acid base status. In contrast, late decelerations are a gradual symmetric decrease and return from the baseline also associated with contractions but delayed in timing.
Compared to early decelerations. The onset nader and recovery of a late deceleration start after the beginning peak and end of a contraction respectively.
Late decelerations represent utero placental insufficiency leading to reduced fetal oxygenation and an increased risk of fetal acidemia.
Now, there are also variable decelerations which are an abrupt decrease in fetal heart rate below the baseline. They often resemble the letter UV or W and are called variable because their timing duration and amplitude fall and rise abruptly.
Variable decelerations may or may not be associated with uterine contractions and represent the fetal heart rate response to umbilical cord compression, which often occurs after membrane rupture.
When less amniotic fluid is present to cushion the cord deeper and more frequent variable decelerations, increase the risk for fetal hypoxemia and acidemia because the flow of oxygenated blood from the placenta to the fetus is reduced while the cord is compressed next up are prolonged decelerations or a decrease in the fetal heart rate lasting between two and 10 minutes.
That may or may not be associated with the uterine contraction. Deeper and more prolonged decelerations are more likely to have adverse effects on fetal oxygenation.
Here's a high yield fact. If a prolonged deceleration or an acceleration lasts more than 10 minutes, it's considered a change in the baseline.
Fetal heart rate. Lastly, a sinusoidal pattern is a smooth sine wave like undulating change in the baseline with a cyclic frequency of 3 to 5 per minute.
It can be associated with severe fetal anemia or the recent use of butorphanol. All right, let's move on to the uterine contraction pattern.

Uterine contraction pattern6:46–7:35

Contractions are quantified by the number present in a 10 minute window averaged over 30 minutes. The normal frequency is five contractions or fewer in 10 minutes and the normal duration is 45 to 90 seconds when more than five contractions are present in 10 minutes.
That's tachysystole. The pattern of contractions can be detected with an external monitor but the strength or intensity of the contractions can only be measured with an intrauterine pressure catheter or IUPC because maternal blood flow to the placenta is reduced during a contraction.
Frequent contractions can lead to decelerations and increase the risk of fetal hypoxemia and acidemia. Now, that were done with the terminology for fetal heart rate and contractions.

Category I7:35–8:08

Lets review some tracings which are grouped into three categories. A tracing pattern with a baseline between 110 and 160.
Moderate variability and absent late or variable decelerations with or without early decelerations or accelerations is a category one tracing which indicates a well oxygenated fetus, a fetus with a category one tracing and normal contraction pattern can be managed routinely.
A category three tracing has at least one of the following absent variability with recurrent late decelerations, absent variability with recurrent variable decelerations, absent, variability with bradycardia for at least 10 minutes or a sinusoidal pattern for at least 20 minutes.

Category III8:08–9:24

This tracing signifies developing fetal hypoxemia, acidemia and possibly permanent injury if this occurs. Prepare for prompt delivery.
Perform a sterile vaginal exam to check for advanced dilation or a prolapsed cord and perform intrauterine resuscitation measures to improve utero placental blood flow by changing the maternal position, administering an intravenous fluid, bullous and stopping the infusion of any uterotonics.
If tachysystole occurs, administer a tocolytic like subcutaneous terbutaline to decrease contraction frequency. Next, assess the response if the tracing is no longer a category three, continue surveillance and consider the appropriate timing for delivery.
However, if the tracing does not improve prompt delivery is indicated. Next, category two, tracings include all other patterns not described as category one or three.

Category II9:24–12:28

Category two, tracings are described as indeterminate and they're not predictive of fetal acid base status. In this situation, assess for the presence of accelerations or moderate variability when either of these are present, evaluate for recurrent or prolonged decelerations, bradycardia or tachycardia.
If none of these are present, continue surveillance and perform intrauterine resuscitation as indicated if recurrent variable decelerations are present, perform an amnioinfusion, which is an infusion of sterile saline into the uterine cavity through an IUPC.
This restores the amniotic fluid volume and cushions the umbilical cord which often improves variable decelerations allowing surveillance to continue.
If recurrent late decelerations are present, placental function is compromised in this situation, perform intrauterine resuscitation to increase utero placental blood flow and continue surveillance.
Now, a prolonged deceleration or bradycardia is more concerning especially if the fetal heart rate is below 100. If either of these are observed, evaluate for maternal hypotension and treat it if present, also perform a sterile vaginal exam to check for advanced dilation or a prolapsed cord and address the underlying cause of the fetal heart rate pattern.
Next, assess the response if the fetal heart rate tracing improves continue surveillance. However, for persistent prolonged decelerations or bradycardia consider prompt delivery.
Fetal tachycardia may reflect maternal infection, placental abruption or fetal blood loss. Address the underlying cause and assess the response if the tachycardia resolves continue surveillance.
However, if tachycardia persists consider prompt delivery. Now, let's discuss category two tracings with no accelerations and absent or minimal variability.
Your first step is to provoke an acceleration or improvement in variability to do this. You can either perform a sterile vaginal exam with stimulation of the fetal scalp or use vibroacoustic stimulation which involves placing a device on the maternal abdomen over the region of the fetal head.
A sound is emitted for several seconds which elicits a startle reflex in the fetus. If an improvement in the fetal heart rate tracing occurs, address any fetal heart rate, decelerations or tachycardia and consider continued surveillance versus delivery.
If there's no fetal response to stimulation, fetal hypoxemia and acidemia may be present and prompt delivery is indicated.
Finally, when uterine tachysystole is present with any fetal heart rate pattern. Assess for the use of uterotonics.

Tachysystole12:28–13:30

If a uterotonic is being administered, determine the fetal heart rate category with category one patterns, decrease the uterotonic to avoid deterioration of the tracing.
If a category two or three tracing is present, decrease or stop the uterotonic and perform intrauterine resuscitation. If tachysystole remains, consider administering a tocolytic to decrease contraction frequency.
Alternatively, if uterotonics are not being used and tachysystole occur spontaneously, assess the fetal heart rate category.
If the tracing is category one, no interventions are required. If a category two or three tracing is present, perform intrauterine resuscitation, assess for the underlying cause and consider using a tocolytic, consider continued surveillance versus delivery based on the response.

Review13:30–14:19

All right, as a quick recap intrapartum, fetal heart rate monitoring provides information about fetal wellbeing during labor.
If a category one tracing is present, the fetus is well oxygenated and routine management is recommended. Category iii tracings indicate the possibility of developing fetal hypoxemia and acidemia requiring immediate cervical examination and intrauterine resuscitation.
If the fetal heart rate pattern does not rapidly improve. Consider prompt delivery.
Category two tracings call for individualized interventions and determination of whether close observation or prompt delivery is appropriate.
If tachysystole is present, management is based on the fetal heart rate pattern and the use of uterotonics.