A new technology for measuring blood oxygen levels of a baby during labor — expected to provide information useful for preventing birth complications — offers no apparent benefit, report researchers in a National Institutes of Health research network.

The technology, known as fetal oxygen saturation monitoring, was designed for use along with electronic fetal monitoring, which tracks the fetal heart rate, to measure changes in fetal oxygen levels. Designers of the new technology hoped that knowing the oxygen status of the baby during labor would provide information on the health of the baby, especially when there were disturbances in the fetal heart rate during labor.

“The results of this study show that while a new technology may appear to be very promising, it’s not possible to know how effective it will be until it can be fully tested under clinical conditions,” said Duane Alexander, M.D., Director of NIH’s National Institute of Child Health and Human Development, which operates the network.


The study, appearing in the November 23 New England Journal of Medicine, was conducted by researchers in the NICHD Maternal-Fetal Medicine Units Network. The study’s first author was Steven L. Bloom, M.D., of the University of Texas Southwestern Medical Center in Dallas.

“Fetal oxygen saturation monitoring offered no apparent advantage in interpreting the meaning of abnormal fetal heart rates,” said Catherine Spong, M.D., an author of the study and Chief of NICHD’s Pregnancy and Perinatology Branch. “Abnormal oxygen readings were common among babies showing abnormal heart rates but they were also common among babies with normal heart rates.”

The study authors noted that a technology developed earlier, electronic fetal heart rate monitoring, was adopted for use in delivery rooms without prior testing. Although electronic fetal heart rate monitoring is in widespread use, the study authors added, there is controversy about the technique’s effectiveness.

The authors of the current study undertook their research to try to find if there was sufficient reason to warrant introducing fetal oxygen saturation monitoring into the delivery room. A previous study of the technology was inconclusive. That study found no overall change in Caesarean delivery rates when fetal oxygen saturation monitoring was undertaken. However, the study found different rates of Caesarean deliveries for two different categories of births. For cases in which the fetal heart rate pattern was abnormal, there were fewer Caesarean deliveries than normal. But there was a higher-than-normal rate of Caesarean deliveries from cases involving dystocia — failure of the baby to move down the birth canal. (Dystocia can result from such causes as the baby being improperly positioned in the birth canal, or from the baby simply being too large.)

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