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Monitoring uterine contractility: mechanisms of the beginning of labour -
transcript
From 23rd Annual Society for Maternal-Fetal
Medicine (SMFM) Conference held in San Francisco, California - February
2003
Monitoring uterine contractility: mechanisms of the beginning of labour
Bob Garfield, MD, PhD interviewed by Hans van der Slikke, MD, PhD
Hans van der Slikke, MD, PhD:
“It is February the 6th, and we are at the meeting of the Society for Maternal Fetal Medicine in San Francisco and next to me is Professor Bob Garfield. A very welcome to you, Bob.”
Bob Garfield, MD, PhD: “Thank you.”
Hans van der Slikke, MD, PhD: “You’re from Texas, Galveston, and yesterday you gave a beautiful presentation about the beginning of labour and it was a presentation loaded with history, but not only that, also a lot of new insights. So before we can talk about the beginning of pre-term labour, it’s necessary to know more about the mechanics of the beginning of labour, and what we learnt from the past?”
Bob Garfield, MD, PhD: “Well, we’ve learned a lot about muscle, uterine muscle, and how it functions, how it contracts, what makes it contract. We’ve also learned a lot about the cervix, the composition of the cervix and somewhat about its function. We’ve learned a little about the hormones, how they control it. There are many unanswered questions.”
Hans van der Slikke, MD, PhD: “What do you think are the most important unanswered questions until now?”
Bob Garfield, MD, PhD: “Well, I think what we’ve tried to focus on in our labs at the University of Texas is basically fundamental mechanisms that control the uterus and cervix and how can you monitor them. We try to focus on methods, new methods for monitoring uterine contractility and cervical function and that’s really what my talk was about on Wednesday.”
Hans van der Slikke, MD, PhD: “And could you elaborate a little bit about these new methods of monitoring?”
Bob Garfield, MD, PhD: “We, in terms of uterine contractility, we’ve known for a long time and we’re taught by really good people, JM Marshall, AI Czapo, and many others, that uterine contractility is controlled by the electrical events of the muscle. Action potentials are generated in the muscle and they propagate over the uterus and this is sort of an area that I began my career in, building upon this whole theory of electrical conductivity and how it occurs in uterine muscle during pregnancy. Then five or six years ago, we began to ask, you know, how can we use this basic information to build a better monitor and we realised that cardiac muscle functions much like the uterus in that it’s also controlled by electrical activity and you can monitor cardiac function very well by putting external electrodes on the chest and measuring electrical activity of the heart, and this is really the mainstay for cardiac monitoring.
In the clinic, you can detect any pathological change in heart muscle by looking at the electrical signals and we began to look if we could see, record electrical signals from the uterus by putting surface electrodes on the abdominal surface of pregnant patients and we did studies not only in humans, but also in animals and these studies were very convincing and it showed that we could record these action-potentials and bursts of electrical activity and they corresponded to the contractions one sees and they change really dramatically during labour, and this offers us the advantage of monitoring pregnant patients non-invasively and it gives us the capability of being able to predict when a woman goes into true labour just from a change in the signals that a woman’s uterus will produce. So it allows us to differentiate between true and false labour, and true and false pre-term labour, which is a big advantage over the equipment we have at the moment.
At the moment, we monitor greater than 95% of our patients with a tocodynamometer and this is an old, crude instrument that roughly measures contractions in the uterus. Then we’ve also focused on an instrument to diagnose cervical functions, cervical changes that accompany labour and we developed a light-induced instrument that measures collagen fluorescence. It measures light-induced fluorescence or LIF and we built prototypes of instruments and used them on animals in the clinic and they provide very good quantitative information about the changes that proceed either term or pre-term labour, the changes in the cervix.”
Hans van der Slikke, MD, PhD: “And what time lag between the start of these changes and the start of the real labour?”
Bob Garfield, MD, PhD: “Well, this is the cervical instrument and cervical function has taught us that the changes in the cervix are really progressive changes. There are chronic changes that occur probably during the last half of pregnancy so there is a progressive decline in the connective tissue of the cervix that leads to softening. On the other hand, the changes in electrical activity are very acute and occur just a few days before a women goes into labour.”
Hans van der Slikke, MD, PhD: “Talking about these cervical changes, do they go together with the ultrasound measurements or shortening of the cervix?”
Bob Garfield, MD, PhD: “Yes, we believe that’s true but we’ve not really compared them. A careful study needs to be done using ultrasound measuring the cervix and then using our instrument, as well. We have not done that, we talked about doing it but we’ve not done it yet.”
Hans van der Slikke, MD, PhD: “So maybe your first, your contractility measurement and the differentiation between real and false pre-term labour could serve as a help for discerning who needs tocolytics and who may not?”
Bob Garfield, MD, PhD: “Yes, exactly. It’s a tremendous advantage in having quantitative instruments for both the uterus and the cervix and there are a lot of potential benefits.”
Hans van der Slikke, MD, PhD: “Thank you very much, Bob.”
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