Physiology of FHR monitoring

Specialties Ob/Gyn

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I am semi-new to L&D. I have been to numerous monitoring classes and remember hearing somewhere there could be a tracing yet the heart could not be mechanically functioning. This had to do with beat to beat variability, or rather, the loss of it. Similar to an adult in PEA. But, we would not know it until the birth obviously. This discussion came up after a stillbirth of a baby that had a FHR tracing up until birth although it was absent variability for quite a while. The other nurses couldn't understand how it could have had a tracing, yet be born lifeless. Am I totally off here or have others heard this????? I have no clue where or when I heard it and can find nothing as I research it. I find when I "google" these types of things, the only info that comes up is for lay people. Would appreciate any info on this so I can share it with my coworkers or admit defeat;)

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It was fetal heart and not maternal, I have had nurses tell me that they were tracing what ended up being maternal even with an internal... and it ended up being a stillborn

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Specializes in Nurse Manager, Labor and Delivery.

Absolutely. One of the main goals of fetal montoring is proving that it is in fact FETAL and not maternal. You should always chart mom's HR AND baby's HR, so that you know that what you are in fact tracing is truly fetal. Even with a scalp electrode, you could be tracing mom ( SE can be on cervix for example). It is especially important to remember that mom's FHR can have variability and have accels (MHR goes up during contraction because of pain). Youi can see this a lot when pushing. Be leary of accels that mirror your contractions. Throw a pulse ox on to differentiate you two HR's to be sure.

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Specializes in Nurse Leader specializing in Labor & Delivery.

EFM would not pick up PEA. It's ultrasonography, not the same technology as an EKG, which picks up electrical activity.

So if the EFM is picking up a heartbeat, then there IS a beating heart. Either the baby's heart, or the mom's heart.

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I should have clarified. This was an IFM, fetal scalp electrode which would not be the same as doppler and would be picking up electrical activity of baby. That's why I compared it to adult PEA. Any thoughts with that in mind?

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Specializes in Ante-Intra-Postpartum, Post Gyne.

I am not really sure, I am new too; but I do know that when the EFM is searching for a FHT it can often pick up the mom's heart rate and double it and may be mistaken for a FHR base line. Us of an pulse ox can help. Remember that what you hear on the monitor is not really the heart itself.

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Again, I am referring specifically to Fetal Scalp Electrode and this is a big difference from doppler, external heart monitor. I have been researching this for several days without much luck but I did find this little "ditty" that some of you might find interesting. I don't belong to the "club" so I can't pull the whole article up, but this gave me just enough to continue researching. I'm just finding this VERY fascinating right now and really think it's something very important for L&D nurses to understand. It can make a little bit of sense of a potentially tragic situation that a nurse may not recognize because there is not a blatant loss of fetal heart rate. http://www.ncbi.nlm.nih.gov/pubmed/1442935?log$=activity

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You *can* pick up a maternal heartrate through a fetal scalp electrode that is properly applied to the fetal scalp when the fetus is deceased. Unfortunately we had just that happen at the last place I worked in. If you have verified by comparing maternal heart rate with the tracing that you have 2 separate heartrates then the fetus is alive. It can not be deceased yet giving off its own independent heartrate.

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Why not? If it is an electrical current, as in an adult, you can have electrical current without mechanical activity and I don't know why a fetal heartrate would be any different. And if you do have two different rates when you have compared it with mom's, who's to say it isn't some type of EMD or PEA. Just a thought. I've emailed this question to some fetal monitoring educators, so hopefully will get an answer.

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Specializes in Nurse Leader specializing in Labor & Delivery.

I guess the question is - what is the technology behind a FSE? Is it measuring electrical activity, or is it measuring something else (bloodflow? I don't know)?

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Specializes in L&D.

A spiral electrode picks up electrical activity. It measures R to R intervals to calculate the rate.

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Specializes in Cardiac.

well your onto something! It definately sparks my interest. Keep us updated!

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