Measuring fetal oxygen does not reduce Caesarean rate, researchers find

November 23, 2006

Measuring the amount of oxygen in the blood of a fetus during labor has no bearing on whether a Caesarean section is performed and does not affect the health of the newborn baby, researchers at UT Southwestern Medical Center have found in a multicenter study.

In the study, appearing in this week's edition of the New England Journal of Medicine, researchers tested whether doctors' knowledge of fetal blood-oxygen levels – measured through fetal pulse oximetry – made a difference in the rate of Caesarean section or condition of the newborn infant.

The device used to measure oxygen levels, called OxiFirst, was conditionally approved by the Food and Drug Administration in 2000. That approval was conditional because of questions regarding the impact of the device on the rate of Caesarean delivery, said Dr. Steven Bloom, chairman of the department of obstetrics and gynecology at UT Southwestern.

"We didn't find a device that could help us, but I think the good news is that these results have served to protect pregnant women from being exposed to equipment and a technology that appears to provide no benefit," Dr. Bloom said.

Obstetricians would like to find better ways to measure the health of the fetus during labor, he said.

The current NEJM study involved 5,341 first-time mothers at 14 university hospitals. Specialized oximetry sensors were fed through the cervix and positioned against the fetus's face to measure the level of oxygen in its blood.

With computers recording the data, the women in the study were randomly placed into one of two groups – in one, the clinicians could see the oxygen readings, and in the other, they couldn't.

The rates of Caesarean section or forceps or vacuum delivery were very close in both groups, as was the overall health of the babies. There also was no difference in labor complications between the two groups.

In 507 cases, the devices were removed because of technical problems or at the request of the mother or doctor.

The study was originally planned to involve 10,000 women, but was stopped early because "the results were conclusive at that point, conclusive that knowledge of fetal oxygen saturation did not improve Caesarean rates or fetal condition," Dr. Bloom said.

The FDA originally approved the device in the wake of a study of 1,010 women in labor with "non-reassuring fetal heart rates," such as speeding up or slowing down of the heart rate. In that study, oximetry greatly reduced the Caesarean section rate due to non-reassuring fetal heart rate patterns, but unexpectedly also greatly increased the number of Caesareans due to other labor complications.

Because those data were inconclusive, and researchers wanted to determine in a larger group whether it was safe to withhold Caesarean sections when oximetry showed normal blood oxygen levels but heart monitors showed abnormal heart rate, and to find whether oximetry improved the baby's health.

Source: UT Southwestern Medical Center