Maternity - L&D, part 6: Fetal Heart Rate Patterns - Normal and Abnormal Findings, VEAL CHOP
by Meris Shuwarger BSN, RN, CEN, TCRN November 18, 2021 Updated: December 07, 2022 6 min read
This article covers fetal heart rate patterns. The Maternity Nursing series follows along with our Maternity Nursing Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.
When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!
Normal findings for fetal heart rate
Normal findings for fetal heart rate (FHR) are the things that we expect to see or that are okay to see.
Baseline fetal heart rate
Normal FHR baseline is between 110 and 160 beats per minute.
Accelerations in fetal heart rate
Accelerations occur when the fetal heart rate accelerates from its baseline level by at least 15 beats a minute and is sustained for at least 15 seconds. These changes in FHR are reassuring, as they indicate that the baby is getting enough oxygen, i.e., everything is okay, and no intervention is required.
Accelerations happen in response to fetal movement and the impact of the world around the fetus. For example, vaginal exams can cause acceleration.
A nonstress test may be administered to measure the fetal heart rate response to fetal movement.
Early decelerations in fetal heart rate
Decelerations occur in distinct types. Early decelerations are benign, meaning no intervention is required. (Below, we discuss abnormal decelerations — late decelerations and variable decelerations).
Decelerations occur in relation to a contraction. So an early or late deceleration refers to when it happens in relation to the patient’s contraction.
If charted, an early deceleration appears as a mirror image of a contraction. As a contraction peaks and then comes back down, the deceleration does the opposite; FHR decreases with the onset of a contraction, bottoms out at the height of the contraction, and then comes back up again. The key takeaway is that the peak of the contraction and the bottom of the deceleration happen in sync, hence the mirror image analogy.
Early decelerations are typically caused by fetal head compression during the contraction. Again, this is benign, and no intervention is required.
Moderate variability in fetal heart rate
Variability has to do with how FHR fluctuates. A normal fluctuation is approximately 6 to 25 beats per minute around the baseline.
Variability indicates that the fetus has a healthy nervous system.
It is important to note what kind of variability is being observed (how great or small is the fluctuation), e.g., absolute variability, minimal variability, or marked variability. A normal FHR would show moderate variability — the reassuring type of variability.
Abnormal findings for FHR: fetal bradycardia
Fetal bradycardia is a fetal heart rate of less than that 110 bpm, which is sustained for greater than or equal to 10 minutes. For example, if there is a drop in FHR, and then 30 seconds later it rises again, this is more likely a deceleration than a fetal bradycardia.
If the baby is experiencing fetal bradycardia, that means it isn’t getting enough oxygen (hypoxia). This indicates there is a problem.
What causes fetal bradycardia?
Fetal bradycardia can be caused by prolonged cord compression, when not enough blood is getting to the baby. This increases the blood pressure, which decreases the heart rate.
Umbilical cord prolapse will also cause a decrease in blood flow, increasing blood pressure and decreasing the heart rate.
Anesthetic medications given to the patient can affect the baby, causing fetal bradycardia.
Fetal heart abnormalities could cause fetal bradycardia. If the heart is not beating properly, the body is not oxygenating appropriately — the fetus is not getting oxygen-rich blood where it belongs.
Treatment of fetal bradycardia
It is important to notify the provider.
Other treatment includes discontinuing medications like oxytocin. Placing the patient in a side-lying position may help. This will reposition the uterus to move it from on top of the umbilical cord. Giving oxygen or increasing IV fluids may also help. It is also important to remain at the patient’s bedside to help reassure them.
Abnormal findings for FHR: fetal tachycardia
Fetal tachycardia is a fetal heart rate of more than 160 bpm, sustained for 10 minutes or longer.
What causes fetal tachycardia?
Fetal tachycardia may be caused by maternal fever. If the patient has a fever or an infection, that will affect their metabolic rate, which in turn affects the fetus. Maternal hypothyroidism will affect the patient’s metabolic rate, which will affect the fetus.
Learn more about metabolic rate and more in our ABG Interpretation Online course, which takes our popular YouTube ABG series to the next level with a purpose-built online learning experience to give you confidence interpreting ABG results. This course was designed to work alongside our Arterial Blood Gas Interpretation Flashcards for Nursing Students.
Fetal hypoxia could also cause fetal tachycardia. If the fetus is not getting enough oxygen, its heart rate is going to increase to try and compensate.
Cocaine use is another cause. Cocaine is a stimulant for the patient, which means it is also a stimulant for the baby.
Dehydration may also cause fetal tachycardia.
Treatment of fetal tachycardia
It is necessary to treat the underlying causes that result in fetal tachycardia. For example, giving an antipyretic for the patient’s fever. Giving IV fluids and oxygen may be helpful if indicated.
Fetal tachycardia may indicate severe fetal distress
Fetal tachycardia accompanied by decreased variability indicates severe fetal distress. In this situation, FHR increases, but variability decreases, and it is imperative to consider immediate interventions to extract the baby.
Abnormal findings for FHR: late decelerations
Late deceleration, unlike early deceleration, is not a mirror image of a contraction. A late deceleration will offset slightly. As the contraction rises and falls, there is a lag in FHR deceleration, that is, the deceleration occurs after the peak of the contraction, not simultaneously with the contraction’s peak.
A late deceleration may also have a prolonged return to baseline, that is, it takes longer for FHR to return to its baseline.
What causes late decelerations?
Uteroplacental insufficiency (sometimes just “placental insufficiency”) is the main cause of FHR late decelerations. The insufficiency refers to a decrease in blood flow coming to the baby, which in turn leads to fetal hypoxia and a drop in fetal heart rate.
Treatment of late decelerations
LION (Left-lying, IV fluids, Oxygen (and d/c Oxytocin), Notify provider).
To treat late decelerations, place the patient in a left-side-lying position. Administer IV fluids and oxygen per order. Discontinue oxytocin. Notify the provider.
Late decelerations may indicate severe fetal distress
If late decelerations cannot be resolved, it may be necessary to intervene to relieve fetal distress. In this instance, the patient should be prepared for surgery, and the baby will be delivered via C-section.
Abnormal findings for FHR: variable decelerations
Variable decelerations are when there is a sharp, dramatic drop in FHR followed by a quick recovery. Variable decelerations are not associated with contractions.
What causes variable decelerations
Variable decelerations are caused by umbilical cord compression. Cord compression leads to increased fetal blood pressure, which leads to decreased fetal heart rate.
Treatment of variable decelerations
Because variable decelerations are caused by cord compression, it is necessary to move the baby off of the umbilical cord. This can be accomplished by placing the patient in the Trendelenburg position, where the head is down, and the feet are up. This uses gravity to shift the position of the uterus, which will shift the position of the baby, potentially moving it off of the umbilical cord.
Another treatment for variable decelerations is to put the patient in the knee-chest position, which is another way of moving the contents of the uterus to attempt to get the baby off of the umbilical cord.
Treatment for variable decelerations also includes administering oxygen and discontinuing oxytocin.
It is also important to notify the provider.
How to treat variable decelerations when amnioinfusion is indicated
Amnioinfusion may be indicated for patients who have oligohydramnios, that is, they have too little amniotic fluid. Amniotic fluid works as a buffer between the baby and the umbilical cord, providing a cushioned environment in the uterus. If there is not enough amniotic fluid, and if the umbilical cord is underneath the fetus, there is no cushion and the cord may be compressed.
Amnioinfusion is a procedure where synthetic amniotic fluid is infused into the uterus to provide a cushioning environment.
This is a handy summary mnemonic of each kind of fetal heart rate variation, as described above.
FHR Pattern Significance
V = Variable → C = Cord Compression
E = Early → H = Head Compression
A = Acceleration → O = Okay (i.e., normal FHR)
L = Late → P = Placental Insufficiency
Hi, I'm Meris with Level Up RN. And in this video, I'm going to be talking to you about fetal heart rate patterns. We're going to talk about normal fetal heart rate patterns, what we expect to see, what kind of things are okay, and then we're also going to talk about some abnormal findings and the causes of those things and what we should do about them. So I'm going to be following along with our Maternity Nursing Flashcards in the Labor and Delivery section. If you have a set, I would invite you to follow along with me. And if you don't have one, you can get a set for yourself on our website, leveluprn.com. Okay. Let's get started.
So first off, let's talk about normal findings for fetal heart rate. These are things that we expect to see or things that are okay to see. So first and foremost, let's just talk about the heart rate itself.
The normal fetal heart rate baseline is going to be between 110 and 160 beats per minute. So we want to first check and see what the rate is of the fetal heart rate so that we can see, is this in the right range? Is it too slow, too fast, that sort of thing.
Now when we talk about accelerations, if you have seen the video about the nonstress test, I talk about what accelerations are in that video. But accelerations are what they sound like. It's where the fetal heart rate accelerates from its baseline level, and that's going to be by at least 15 beats a minute. So it's going to increase by 15 beats per minute, and that's going to be sustained for at least 15 seconds. So that's what an acceleration is. And this is a good thing.
This is actually really reassuring that the baby is getting enough oxygen and things are okay because accelerations happen in response to fetal movement and just kind of the impact of the world around them. Things like vaginal exams also can cause acceleration. So these are good. These are normal. These are reassuring. We like them.
Now, decelerations, decelerations are also what they sound like, but we have a couple of different types. So in this case, when we're talking about things that are okay or normal, we're talking about early decelerations. And what this means is that it's in relation to a contraction. So when we talk about early or late, we're talking about where does it happen in relation to the patient's contraction?
So an early deceleration is going to be a mirror image like a flipped image of the contraction. So the contraction is going to come up like this. It's going to peak and come back down. The deceleration is going to come down like this. It's going to bottom out and then come back up. But the peak of the contraction and the very bottom of the deceleration are going to match up. They are happening in sync, so they should look just like flipped versions of one another.
Now, an early deceleration, this is going to be benign. This is not something where we need to intervene. This is typically because of head compression. So that early deceleration in fetal heart rate is going to be caused by head compression, compression of the fetal head. And like I said, that mirroring is going to be the most important thing to understand when you're looking for, is it early or is it late?
Now, variability, variability has to do with, how does the heart rate change second to second?
So we should see fluctuations of the fetal heart rate by 6 to 25 beats per minute around the baseline. So that's why if you ever look at a fetal heart rate tracing, most of the time you're not just seeing a straight line across that's showing you it's 120 beats a minute, and it's just really staying there. That is not normal.
So the variability indicates that we have a healthy nervous system. A healthy nervous system of the baby is going to be demonstrated with this moderate variability. Remember that variability is a term that can be used-- you have to qualify it. You have to say how much there is. So you can have absolute variability. You can have minimal variability. You can have marked variability. But what we want is to see moderate.
Moderate variability is the reassuring type of variability.
So now let's move on to abnormal findings. So from this point out, we're talking about things that are not normal, not expected, and probably not okay.
So first up, we're talking about fetal bradycardia. Now, remember that 110 to 160 is the normal baseline.
So fetal bradycardia is going to be anything that is less than that 110. However, it has to be sustained for greater than or equal to 10 minutes. So we're not going to call it fetal bradycardia if we have a drop in the heart rate and then 30 seconds later it comes back up, right? That would probably be more a deceleration.
But why does this happen? Well, there's a lot of reasons that fetal bradycardia can happen. If we have prolonged cord compression, we're not getting enough blood to the baby. That's going to increase the blood pressure. It's going to decrease the heart rate. Umbilical cord prolapse, same kind of situation there. Anesthetic medications, so medications given to mom can affect baby. So that has to be a consideration as well. And fetal heart abnormalities, of course, could cause that as well. But if I am not-- if my heart is not beating appropriately, I am not oxygenating my body appropriately, right? I'm not getting that good oxygen-rich blood where it belongs. So when you think fetal bradycardia, you've got to think, "This baby isn't getting enough oxygen." That's a big problem.
So things that we can do for it, side-lying position is always a good choice, repositioning the uterus so that it may not be on the umbilical cord, for instance, can be helpful, oxygen, IV fluids, but most importantly, we need to notify the provider, right? That's going to be really important, but we want to stay at the bedside with mom too.
Now, on the flip side, fetal tachycardia.
So that's going to be anything above 160 beats a minute, sustained for 10 minutes or longer, right? So same parameters, just on the opposite side of the spectrum.
Now what can cause this? A big one is maternal fever. So if mom has a fever or an infection, then that's going to affect mom's metabolic rate, which in turn is going to affect baby, also, fetal hypoxia, right? If I'm not getting enough oxygen, my heart rate is going to start to go up to try and compensate for that. Maternal hypothyroidism, again, anything that's affecting mom's metabolic rate will also affect babies. And then cocaine use, cocaine use, it's a stimulant for mom. Therefore, it's a stimulant for baby.
So what are we going to do about that? Well, we need to treat the underlying cause if that is the case, so giving an antipyretic for mom's fever, for instance. IV fluids and oxygen, of course, are going to be helpful if they are indicated for that purpose. But there's a line here that I would like to draw your attention to if you have this card as well.
Fetal tachycardia accompanied by decreased variability is indicative of severe fetal distress, so heart rate goes up, but variability goes down. That's a really bad, scary thing. We need to be thinking about immediate interventions to get this baby earthside.
Okay. Up next, we're going to talk about late and variable decelerations. We already talked about early decels, right? Those are those exact mirror images of the contractions. Those are okay. They're caused by head compression. That's all right. But when we talk about late and variable, these are not normal findings.
So a late deceleration is not going to be that perfect mirror image of the contraction. Instead, it's going to be offset slightly. So what you're going to see is that the contraction comes up and goes down, but the base of that deceleration of the heart rate is going to come after the peak of the contraction.
So it's later than the peak of the contraction. That's a late deceleration. So that can also have a prolonged return to baseline, meaning that it takes longer for it to kind of come back up to where it should be. So those are the scary ones that we don't like to see.
And the biggest cause here is going to be uteroplacental insufficiency. You can sometimes hear this just called placental insufficiency. But essentially, we have decreased blood flow coming to the baby, which in turn is going to lead to fetal hypoxia. And that's where we see that drop in fetal heart rate.
So we have a cool chicken here right here on this card. We have a cool chicken that I want to point out because I love this one. I think it's very helpful. It's how to treat any sort of deceleration, but specifically, the late one here we're talking about is LION. And I would actually say it's LIONS, but I'll get there in a second. So LION is for left-lying positions. We're going to turn mom onto the left side. I is for IV fluids. We're going to administer IV fluids per order. O is for oxygen, and you can also remember the O means to discontinue oxytocin. O for oxytocin, discontinue it. And then N for notify provider. So those are the letters in LION to remember treatments for late decels. I would say that the S is to prep for surgery. So if we have late decels and we're not able to resolve them, doing these other LIONS interventions, then preparing for surgery, delivery via C-section is going to be the next thing to do.
Moving on to variable decelerations. Variable decelerations, I remember V for variable and they kind of look like a V. They have a very sharp, dramatic drop and usually a pretty quick recovery. So the fetal heart rate tracing, when you see a variable decel, it's going along. It drops. It comes back up, and it keeps going along.
Now, the cause of variable decels, that's going to be umbilical cord compression. So cord compression is going to lead to increased fetal blood pressure, which then is going to lead to decreased fetal heart rate. So with this one, we need to get the baby off of the cord. So how can we do that?
Well, we can put mom in the Trendelenburg position. Trendelenburg is where the head is down, and the feet are up. So if you have a patient laying flat, then you're going to tip them like this, and hospital beds have the ability to do that. You're going to put the head down, feet up. That's going to use gravity to shift the uterus, shift the baby, potentially shifting the baby off of the cord.
Another one would be knee-chest position, again, to try and move the contents of the uterus around to get baby off of the cord. Now, again, we're going to administer oxygen, discontinue oxytocin, notify the provider. That's all important stuff all of the time, right?
But amnioinfusion may be indicated. And this is for patients who have oligohydramnios, meaning they have too little amniotic fluid. Well, that amniotic fluid works as a buffer and a cushion, so it would be between baby and the cord and providing all of this nice, cushioned environment. If I don't have enough, then if that cord is underneath baby, there is no cushion there. So we can do an amnioinfusion, which again, is what it sounds like. We are infusing synthetic amniotic fluid into the uterus to provide that sort of cushioning environment as well.
Now, this card is my favorite one to sum up everything we just talked about. This is the VEAL chop card. So we have it spelled out here, right for you, in big letters. And it's a very clear card so that you can see exactly what we're talking about.
So VEAL chop, and I want you to write it out vertically, not horizontally, vertically, VEAL and chop so that the letters line up.
So V is for variable, and the C is going to be for cord compression. They line up.
Then we have the E is for early, so early deceleration lines up with the H, which is for head compression.
The A is accelerations, which lines up with the O, which means, okay. This is okay. This is a good thing. We're not worried about it.
And then L is for late as in late decelerations, which lines up with the P for placental insufficiency. So when you use this mnemonic right here, when you use this, you can line up and see the cause of each different kind of fetal heart rate variation.
So I hope that review was helpful for you. But now I'm going to give you some quiz questions so that you can test your knowledge and see if you picked up on some of the really key points of this video.
Okay. So first up, I want you to tell me what is the normal baseline for fetal heart rate? Think about that, normal baseline for fetal heart rate.
For which fetal heart rate pattern would you want to place the mom in Trendelenburg or knee-chest position?
What does moderate variability in the fetal heart rate indicate? What does moderate variability indicate about the fetus?
Lastly, I want you to think about and tell me what is the cause of late decelerations? So what is the underlying cause of a late deceleration?
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