No good reason to invest in new fetal oxygen monitor

Nov 23 2006

New technology for measuring blood oxygen levels of a baby during labor which was intended to provide information useful for preventing birth complications, apparently offers no apparent benefit.

Researchers from the National Institutes of Health research network say 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.

The designers hoped that knowing the oxygen status of the baby during labour would provide information on the health of the baby, especially when there were disturbances in the fetal heart rate during labour.

The study was conducted by researchers in the The National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network, who say the technology offered no apparent advantage in interpreting the meaning of abnormal fetal heart rates and was halted early because of overwhelming evidence that the technology was ineffective.

The study's first author Dr. Steven L. Bloom, chief of obstetrics and gynecology at the University of Texas Southwestern Medical Center in Dallas, says they could find no reason to use the technology.

For the study, doctors monitored the fetal oxygen levels in 5,341 women pregnant for the first time at 14 university hospitals in the United States.

As soon as the mother's waters broke, a sensor was inserted into the uterus and placed against the fetus' temple or cheek.

The sensor then provided an up-to-the-minute reading of the fetus' oxygen levels.

The women were then randomly separated into two groups; in one group, doctors could read the oxygen levels, while the information was hidden to the other group.

In both groups, about 26 percent of deliveries were done by C-section and no difference between the two groups was found regarding stillbirths, infections or other newborn problems.

Dr. Catherine Spong, M.D., a co-author of the study and chief of NICHD's Pregnancy and Perinatology Branch, says abnormal oxygen readings were common among babies showing abnormal heart rates but they were also common among babies with normal heart rates.

She says fetal oxygen saturation monitoring offered no apparent advantage in interpreting the meaning of abnormal fetal heart rates.

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 as a previous study of the technology was inconclusive.

The U.S. Food and Drug Administration, which approves new medical devices for safety and effectiveness, therefore only granted provisional approval for fetal oxygen saturation monitoring until the new technology could be proven effective.

The current study was designed to settle unresolved questions about the new technology.

The fetal oxygen monitors cost about $10,000 each and the sensors about $150 apiece.

The research was funded by the National Institute of Child Health and Human Development, part of the National Institutes of Health.

In a statement, the FDA said it was reviewing the study and may revise the label on the monitors or inform hospitals about the findings, but is unlikely to withdraw its approval for the technology based on this study alone.

The study is published in the November 23rd edition of the New England Journal of Medicine.