A Childbirth Technology Disappoints

As every 21st century mother knows, technology has become a routine part of delivering a baby in the hospital. One big advance: fetal heart rates are now routinely tracked during labor to be sure that there are no major and worrisome changes that would require an emergency Cesarean delivery. But monitoring heart rates alone doesn’t always provide enough information about risk. Researchers had hoped that a new technology, called fetal pulse oximetry, or fetal oxygen saturation monitoring, would help doctors assess the severity of a change in the fetus’s heartbeat by providing additional information about the baby’s condition. If the fetus had an abnormal heartbeat but good oxygen levels, the thinking went, doctors might be able to avoid performing unnecessary C-sections. A new study released Wednesday in the New England Journal of Medicine, however, found that that thinking did not bear out. Scientists tested oxygen saturation monitoring on the fetuses of 5,341 women during labor and found that the technology had no apparent benefit in interpreting abnormal fetal heart rates. NEWSWEEK’s Claudia Kalb talked to Dr. Catherine Spong, an author of the study and chief of the National Institute of Child Health and Human Development. Excerpts:

NEWSWEEK: Prior to doing this study, what was known about the effectiveness of monitoring fetal oxygen levels?

Dr. Catherine Spong: An earlier study found that Cesarean deliveries were significantly lower if doctors used this technology when there was an abnormal heart rate pattern. That sounds good. You use this technology and you don’t have to do so many Caesareans. Based on the study, the company that manufactures the technology got conditional approval from the FDA to use the device for babies who had an abnormal heart rate tracing—an abnormal heart rate over a period of time. At the same time, though, that study found an increase in C-section deliveries for dystocia—a condition that occurs when the baby is either too big or isn’t positioned correctly and therefore can’t be delivered vaginally. So overall, there was no difference in Cesarean deliveries in the study.

Why did you do this second study? How did it differ?

We did the study to see whether or not this technology was beneficial in reducing the overall C-section rate as well as C-sections for abnormal heart rate patterns. And the design of this study was a little bit different. In this study, all patients had the oximeter. In half of them, the readings were blinded so physicians didn’t know what they were. In the other half, physicians knew.

What was the goal of oxygen saturation technology?

To assess the well being of the baby and to determine: do you need to move to delivery right now? Or is the baby doing ok even though the heart rate tracing is abnormal?

Why is heart rate monitoring so important?

Normally, we monitor the baby’s heart rate continuously during labor and we monitor mom’s contractions continuously. The baby’s heart rate is constantly changing. You might have an average of 140 beats per minute. But there’s short-term variability as well as longer term variability. The heart rate goes up and down as the baby moves and gives you an idea of how the baby is doing inside the womb.

Say a contraction occurs—the amount of blood to the baby goes down. Typically a baby who’s doing well has no problem with contractions. But a baby who’s not doing well might have its heart rate go down because it doesn’t have the reserve it needs. It doesn’t have the ability to sustain a decrease in blood flow. It’s as if you have somebody very ill and you put them on a treadmill. They’re not going to be on the treadmill very long. A baby who isn’t doing well inside the womb only has a certain amount of reserve.

So we’re constantly measuring the baby’s heart over time. Sometime it’s normal, sometimes concerning, sometimes abnormal. The hope was that knowing the saturation of oxygen in the blood would provide more information when we had those abnormal tracings. In general, when  [Kalb, Claudia]   you have abnormal tracing, in some way you need to be reassured that the baby is doing ok. You want to be reassured and if you’re not reassured, you’ll likely move to delivery in some fashion.

How is the oxygen testing done?

A flat straw is placed into the womb overlying the baby’s cheek to monitor how much oxygen saturation the baby has. Oxygen is something we all need in our tissues. The hope was that the knowledge of what the baby’s oxygen saturation is would allow the physician interpreting the heart rate tracing to have more information and make better decision as to the status of baby. Is the baby doing well in there or should we move to do a C-section earlier?

What do you normally do if the heart rate tracing is abnormal?

It depends on the whole clinical situation. If you have someone who’s not yet in active labor and the fetus has an abnormal heart rate tracing and there are already complications for mom and baby, you might decide that it would be safer to deliver her by C-section. If the heart rate tracing is very late in the process, you might allow delivery to occur naturally or assist delivery.

One of the ways to assess how the baby is doing is to take a sample of the baby’s blood from the baby’s scalp and look at acid base or PH level of the baby and the oxygen status of the baby. The hope was that this technology could provide that same information in a non-invasive way.

What were the study’s conclusions?

What we found was that knowledge of oxygen saturation did not reduce the overall C-section rate for abnormal tracings, did not reduce the C-section rate for dystocia, and did not improve outcomes. It was hoped this was something that would really be beneficial and it didn’t turn out to be the case.

Did you expect the C-section rate to go down?

The hope was that you would be reassured by the oxygen saturation and perhaps you could decrease Cesarean deliveries.

Are C-section rates too high in the United States?

It’s hard to say what the correct Cesarean delivery rate is. What we want is to optimize the outcome for mom and baby. Regardless of what the rate is, you want the best outcome for mom and baby. The safest and healthiest outcome is a normal, natural, uncomplicated vaginal delivery for both mom and baby. The more caesareans an individual has, the more risky. If you can have an uncomplicated vaginal delivery, that’s the ideal goal. That’s the lowest risk.

Is the study outcome a big blow?

I don’t know that it’s a big blow. For us as obstetricians, we always want to be able to get more information to improve the outcome for both the mom and baby. It was really a hopeful technology. It’s disappointing that it didn’t help, but we’ll remain hopeful that we’ll find other approaches. I think what the study is saying is that oxygen saturation didn’t provide additional information beyond what we already had with abnormal tracings. It’s not that it’s not useful or didn’t give good information, but it didn’t help us manage and monitor the baby. It’s another technology that we don’t need to burden the patient with.

Some would argue that delivery has gotten too high-tech, that there’s too much monitoring going on in the delivery room today. Your thoughts?

All we’re trying to do is to optimize the outcome for the baby. Monitoring the baby’s heart rate and mom’s contractions, making sure labor is progressing normally and that you’re not doing harm. That’s the goal of the obstetrician and the nurse taking care of the patient. What I’m happy about is that we were able to evaluate this technology before it was widely implemented. It’s very hard to remove a technology, especially something that seems inherently so good. But realizing that it wasn’t beneficial, I think it [Kalb, Claudia]    is  very helpful for physicians and women not to have additional monitoring going on if it’s not helpful.