How exactly do those contraction monitors work?

[Synchro246]

The external ones that strap around a woman's belly--how do they work? (what are they called toco. . .)

I've heard soooo many stories of a woman going in to get monitored to find that she's contracting regularly. All the time I think I'm having a ctx based on how *I* feel then I press my hands to my tummy and it feels like nothing special so I think I must be imagining the ctx. I wonder if a monitor would pick up on something I'm not feeling.

[hippiemom]

HI Laura,
that is my name too
Those tocos are like ultrasound monitors partially, for monitoring the baby's heartrate. The other is a 'transducer' which uses/reads pressure to determine contractions.

In my opinion as a doula, CBE, and mother of 3, women know when they are having an effing contraction Nurses looking at a machine to tell if the women are having contrax (even unmedicated women, come on!) really bothers me. I ask the woman, or feel her belly. Some of us say we can tell how strong her contrax are by her FACE more than anything. IMO if you are not feeling contrax yourself then you are not in active labor. You will feel them honey, and you will wonder how you ever thought it possible that you would not... are you in your final weeks of pregnancy waiting to go into labor by any chance?

[doctorjen]

The tocometer (which is the monitor that monitors contractions) works as a simple pressure change monitor. It detects changes in pressure. A contraction shows up usually as a smooth hill - pressure gradually increases, peaks, and goes back down gradually. It is the heart rate monitor that is ultrasound. An external contraction monitor also picks up other pressure changes - you will see spike type things with movement, or sometimes see small bumps with each breath. An external monitor can only tell when a contraction is happening - not how strong they are. How high the pressure change registers has to do more with the shape of the mama, where you put the monitor on her belly, and a lot of external factors like that. Sometimes, particulary with fluffier moms, it's hard to trace contractions at all if you can't get the monitor situated well over the uterus. It is not at all uncommon to see huge-looking contractions that one woman can barely feel or not feel at all, and have another woman in active, active labor with contractions that visually barely measure anything. Sometimes, care providers get caught up thinking someone must be laboring because contractions are tracing, or someone must not be laboring because their contractions don't trace or look small. It's important to remember that the monitor can only tell you when a contraction is happening, not anything about it's strength.

An internal contraction monitor (called an intrauterine pressure catheter, or IUPC) can usually accurately measure the strength of a contraction.

[Synchro246]

Originally Posted by doctorjen

The tocometer (which is the monitor that monitors contractions) works as a simple pressure change monitor. It detects changes in pressure. A contraction shows up usually as a smooth hill - pressure gradually increases, peaks, and goes back down gradually. It is the heart rate monitor that is ultrasound. An external contraction monitor also picks up other pressure changes - you will see spike type things with movement, or sometimes see small bumps with each breath. An external monitor can only tell when a contraction is happening - not how strong they are. How high the pressure change registers has to do more with the shape of the mama, where you put the monitor on her belly, and a lot of external factors like that. Sometimes, particulary with fluffier moms, it's hard to trace contractions at all if you can't get the monitor situated well over the uterus. It is not at all uncommon to see huge-looking contractions that one woman can barely feel or not feel at all, and have another woman in active, active labor with contractions that visually barely measure anything. Sometimes, care providers get caught up thinking someone must be laboring because contractions are tracing, or someone must not be laboring because their contractions don't trace or look small. It's important to remember that the monitor can only tell you when a contraction is happening, not anything about it's strength.

An internal contraction monitor (called an intrauterine pressure catheter, or IUPC) can usually accurately measure the strength of a contraction.

Thanks
I don't understand how a flat thing on an outside of something else can measure pressure though. I get how the IUPC does--it's mechanical so it's easy for me to understand, I guess.
When I was in labor last time I was too active for the external Toco to work so they had me pressing a button every time I had a contraction. Then they stopped believing that I was hitting the button at the same time every ctx (baby was having normal decels, I could tell they were normal) so they pressured me into a IUPC. I guess it worked out, but yuck anyway. (oooh and while we're on the subject-- What are the risks with IUPCs? I don't think they told me of any risks when I agreed. . .)
Really though, how does a flat object on the outside of a uterus measure pressure? Sorry if I'm being thick

[Synchro246]

Originally Posted by hippiemom

You will feel them honey, and you will wonder how you ever thought it possible that you would not... are you in your final weeks of pregnancy waiting to go into labor by any chance?

I am waiting. . . it's very different from last time and my body keeps faking me out.

[Jane]

Next time you see one, look at it, touch it, flip it over and see the little button on the mom's side. If it's attached, and you touch the button (depress it), it will read the pressure. That's all it is. There are electronics to interpret in the input, but it's a button on a strap.

[Synchro246]

Originally Posted by Apricot

Next time you see one, look at it, touch it, flip it over and see the little button on the mom's side. If it's attached, and you touch the button (depress it), it will read the pressure. That's all it is. There are electronics to interpret in the input, but it's a button on a strap.

Oh! I guess I never looked closely. How lame of me! Thanks!!

[doctorjen]

Some have a button on the side that goes against the mom, some are flat, but the flat side is mobile to move and detect pressure.

[cfiddlinmama]

I just wanted to nod my head at what doctorjen said. I went into the hospital with preterm labor. There were smallish regular contractions registering on the monitor. The resident looked at the readout and said "are you even feeling those little tiny contractions?" Um yeah. I was a second time mom and the ctx were strong enough for me to drive 1.5 hours to the big hospital. They didn't believe I was in labor because they were registering so small on the readout. I don't have much faith in them at all. You would think providers would just talk to women instead of looking at a piece of paper. What a novel concept! :

OP - Sending you good strong peaceful labor vibes! You'll know when it's time!