Fetal Heart Tone Monitoring: Accelerations & Decelerations Explained

Hey everyone, it's Nurse Sarah and in this video I'm going to go over fetal heart tone monitoring. And as always,

whenever you get done watching this video, don't forget to access the free quiz. So, let's get started. Fetal heart

tone monitoring is used to help us assess a baby's status during that labor process. And we can measure it various

ways. One way is through internal monitoring. And this is where a spiral electrode is inserted up through the

cervix and put in the baby's scalp. Now, this is really reliable, but it's invasive to the baby and the patient.

Another way is through external monitoring, and this is where they take an ultrasound transducer and put it

across the mother's abdomen. So, with this, it's not going to be as reliable as internal, and it can be affected by

the baby's position, but it's less invasive. Now, whenever you're looking at this fetal heart tone monitoring,

there's a few things you want to be familiar with. First up on the top, typically what you're going to see is

the fetus's heart rate. You have numbers on the side that tells you heart rate ranges. And then you're going to have

this line on this grid that's going to be squiggly. And all it's showing you is how the baby's heart rate is trending. A

normal fetal heart rate is anywhere between 110 to 160 beats per minute. And then below that, you're going to see

another line. And this line is going to represent mom's contractions. So just to review for your maternity exams, let's

talk about the little parts of a contraction. So with this on the monitoring, what you're going to see is

you're going to be able to see the increase of the contraction when it's coming on, hence when it's building.

This is the increment. Then you're going to see the peak of the contraction, the acme. And then you're going to see where

the contraction starts to let off. It hence decreases its decrement. And then you can see the relaxation period. And

this section of the monitoring is going to allow you to see mom's contractions, its frequency, its intensity, and so

forth. So, first up are accelerations. The word acceleration means an increase in rate. And that's what we're talking

about with our baby. This is a temporary increase in the fetus's heart rate. So, for a term fetus, this is a heart rate

greater than 15 beats per minute above its baseline for at least 15 seconds, but no more than 2 minutes. And this can

happen at any time. Typically, what causes it is that the fetus is moving or we have contractions going on. Now, for

this, there's no interventions that are needed. This tells us that our baby is healthy and responding like they should

and they're getting proper oxygenation. Next are early decelerations. And what you want to remember with this is that

the fetal heart rate is going to mirror mom's contractions. So, the baby's heart rate is going to stay within normal

range from 110 to 160. So, you will start to see that the baby's heart rate will dip at the start of mom's

contractions, but it's going to recover at the end of mom's contraction. And here on this screen, you can see you see

baby's heart rate, mom's contraction. They're literally mirroring each other. When mom's contraction starts, that

baby's heart rate dips a little bit, but it's staying within normal. And then at the end of the contraction, that heart

rate recovers nicely. So, what is the cause of this? Well, it's resulting because of head compression. The baby's

head is in that canal. That contraction is happening which is compressing that head. Well, it's also compressing the

vagus nerve which is temporarily causing that heart rate to fall. But once that contraction starts to let up, relieves

that compression, hence that Vegas nerve is not being compressed. So that heart rate recovers nicely. Now with this,

there's no intervention needed. You want to continue to monitor and document. Early decelerations are normal. And then

there's variable decelerations. This is where we have these sudden sharp drops in the fetal heart rate where it's going

less than 110 beats per minute. And then eventually it will try to recover to baseline. So with this, notice on the

bottom we have mom's contractions. When mom's contraction happens, all of a sudden, bam, that heart rate, it drops

down. And it drops so sharply and it tries to increase. And when it tries to increase, it creates this like V or

Ushaped pattern. And that's how I remember this. Remember that variable, we're talking about variable

deceleration starts with V. So whenever this baby's heart rate dropped and so suddenly, it creates like these V- like

shapes. Now, what causes this type of deceleration? Well, it's typically caused by umbilical cord compression. So

whenever mom's having a contraction, it's compressing that umbilical cord. Well, when we compress umbilical cord,

that's literally baby's lifeline. that's going to decrease oxygen. Whenever it does that, that stresses baby's heart

out and hence that heart rate drops. So, this is not a good thing and it requires nursing interventions. So, what you want

to do is you want to change mom's position. There's various positions you can do. You can do knee to chest or you

can do trendelenburgg. This is going to help relieve that compression and help increase oxygen to baby so we don't drop

that heart rate. You also want to give some supplemental oxygen. So about 8 to 10 liters, whatever your protocols say,

via mass to mom so we can get some oxygen to baby. If mom has ptocin running, you want to stop that cuz it

can make this worse. And if need be, you need to perform a vaginal exam to see if you do have maybe cord prolapse and

contact the midwife or doctor because we need immediate intervention. And then lastly, we have late decelerations.

These accelerations are called late because the baby's heart rate is dropping later, hence after the peak of

mom's contractions and doesn't recover until well after that contraction has ended. And here you can see that we have

mom's contraction and then baby's heart rate drops after the peak of that contraction and doesn't recover until

well after that contraction is over. Now, what is causing this type of deceleration? Well, it's typically

caused by uterero placental insufficiency. So, that placenta is not working like it should. It's not

delivering the oxygen that the baby needs. So, this is not good. It requires intervention. Therefore, what you're

going to do, you're going to do well the steps that you did for variable. You're going to change mom's position. You are

going to administer oxygen. You're going to stop ptocin if it's infusing. Also, you may be required to infuse fluids

because this will help provide some profusion to the placenta. and you want to notify that midwife or doctor because

this patient needs immediate intervention and probably needs an emergency C-section. Okay, so that wraps

up this review. And if you're studying for your maternity exams and you'd like some more resources to help you study, I

have a study guide you can get at nurser.com in digital format or you can get this at amazon.com in paperback.

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