WEDNESDAY, Nov. 22, 2006 (HealthDay News) -- A new test that measures how much oxygen is circulating in fetal blood just before birth has no effect on whether delivery is done by Caesarean section or not, researchers report.
In addition, fetal blood oxygen doesn't appear to reflect the health of the newborn -- suggesting there's no real reason to use the test.
"We found absolutely no difference in Caesarean sections," said Dr. Steven Bloom, lead author of a study appearing in the Nov. 23 issue of the New England Journal of Medicine. "Given the available evidence -- and I believe we are the most definitive study -- there is no apparent benefit of this technology, which is not to say there won't be possibilities in the future."
Experts say the findings won't have much impact on obstetric practice.
"This is not a technology that is widespread in the U.S.," said Dr. Michael Divon, chairman of obstetrics and gynecology at Lenox Hill Hospital in New York City. "It also becomes somewhat irrelevant because so many C-sections are elective. It's very difficult to come up with a technology which decreases the C-section rate when so many are being done just because the patient wants it."
The C-section delivery rate stands at a record high in the United States as of last year, accounting for 30.2 percent of all births. That represents a 46 percent rate increase since 1996, according to the U.S. Centers for Disease Control and Prevention's latest statistics. C-sections carry several risks, including infection and a longer recovery time.
"Whatever we're doing obviously is not working because the C-section rate has reached a peak," said Dr. Abdulla Al-Khan, director of fetal diagnosis and therapeutics at Hackensack University Medical Center in Hackensack, N.J.
The device used to measure fetal oxygen in this study, called the OxiFirst Fetal Oxygen Saturation Monitoring System, was conditionally approved by the U.S. Food and Drug Administration in 2000 for use as an adjunct to electronic fetal monitoring. Electronic fetal monitoring remains the most widely used tool to evaluate the health of a baby during delivery. Much of the concern has to do with preventing cerebral palsy, which had been thought to be due to a lack of oxygen during labor.
Fetal pulse oximetry had been developed over a decade and generated a great deal of "buzz" in obstetrics circles. "People though this technology could potentially meaningfully change the way we manage women during labor and really help us assess the well-being of a baby during labor," Bloom explained.
FDA approval was based on a study of more than 1,000 women whose pregnancies were complicated by fetal heart rate problems. But although fetal pulse oximetry reduced the rate of C-sections due to "non-reassuring fetal heart rate patterns," it also greatly increased the number due to other complications.
"The results were a little perplexing," said Bloom, who is chairman of the department of obstetrics and gynecology at the University of Texas Southwestern Medical Center at Dallas.
Shortly after the release of those findings, the American College of Obstetricians and Gynecologists issued a strong statement recommending that obstetricians in the United States not adopt the device as a routine practice until further studies were conducted.
Enter the current study, which was conducted by the U.S. National Institute of Child Health and Human Development's Maternal/Fetal Medicine Units Network. "We tried to validate the findings," Bloom said.
This study involved 5,341 first-time mothers who were randomly assigned to receive either "open" or "masked" fetal pulse oximetry. In the former group, the doctor could see fetal oxygen saturation values while, in the latter, the values were recorded, but the physician could not see them.
For the study, special oximetry sensors were positioned near the fetus's face so as to be able to measure blood oxygen levels.
As it turned out, there was essentially no difference in overall rates of Caesarean delivery between the open and masked groups (26.3 percent in the open group and 27.5 percent in the masked group).
Although the study was originally designed to involve 10,000 women, it was stopped early because the results were so conclusive.
"We don't know why fetal pulse oximetry didn't work. We have given it a good chance. We tried it thousands of times," Bloom said.
Others faulted the study for excluding women with problems. "They essentially went for a completely normal group of patients, and we know that in that set of babies it's very difficult to cause bad things no matter what your testing is like," said Dr. Edward Davis, director of maternal fetal medicine at Hackensack University Medical Center.
There is still, however, a need for more successful technology, Bloom maintained.
"Electronic fetal monitoring has limitations, and there's just no getting around that," he said. "There is a need in obstetrics to develop additional tools to help us evaluate the well-being of the baby."
"Electronic fetal monitoring has a 50 percent false-positive rate so half the time we do a C section for [irregularities] it turns out the baby was doing fine," said Dr. Jesus Alvarez, senior fellow of maternal fetal medicine at New Jersey Medical School in Newark. "We're looking for other tools as this one clearly doesn't work."
It may also be that problems need to be picked up earlier on. "The incidence of cerebral palsy has not decreased," Al-Khan said. "That tells us this is a process that happens early in pregnancy. We're picking things up when the damage is already done."
More information
To learn more about a healthy pregnancy, visit the U.S. Centers for Disease Control and Prevention.
