March 19, 2001 -- Kathy Schuler dreaded the thought of a cesarean section. She had seen friends struggle through recovery and hated the idea of being cut open. But after five hours of labor and signs that her baby might be in trouble, there usually was no other choice in cases such as hers. Until now.
A new device called the fetal oxygen saturation monitor, designed to measure the level of oxygen in a fetus' blood, is giving doctors, nurses, and expectant mothers the reassurance that babies who may seem to be struggling during labor are actually fine.
"From my perspective, this is one of the most significant technological advancements in obstetrics in a long time," says Thomas J. Garite, MD, professor and chairman of obstetrics and gynecology at the University of California-Irvine. "It is technology that allows us to do the right thing for the right reason, and that is an important advance."
For the past 30 years, doctors and nurses have monitored fetal condition through the heart rate monitor -- a belted device that is strapped around the mother's belly. However, about 30% of all labors (about 1.2 million births per year) will produce an abnormal or "nonreassuring" heart rate at some point, according to the CDC. Such an abnormal rate could be due to a serious concern such as the baby receiving an insufficient amount of oxygen. But it also could be due to an inconsequential one like the baby falling asleep. Unfortunately, the heart monitor is usually not capable of distinguishing between the two, leaving the obstetrical team with the difficult decision of whether to allow labor to continue or proceed with a C-section.
About seven of every 10 cesarean sections performed because of presumed fetal distress are unnecessary, says Kathleen Simpson, PhD, RN, a nurse researcher in labor and delivery at St. John's Mercy Medical Center in St. Louis. However, the fetal oxygen saturation monitor, approved by the FDA last year, has the potential to change that. Called by the FDA "the first major technological development in fetal monitoring" in decades, the OxiFirst system takes some of the guesswork out of deliveries.
"It gives more information and objective information so we can say, 'This baby needs to come out and needs to come out in an emergency fashion,' or 'This baby can tolerate labor a little longer and perhaps have a vaginal birth,'" says Simpson, a co-investigator in the multicenter study on fetal oxygen monitors.
In the past, medical teams have used fetal scalp blood sampling to determine fetal oxygen levels, but Simpson tells WebMD the process of obtaining the blood from the baby's scalp is invasive, and often must be repeated several times.
The fetal oxygen monitor, on the other hand, usually causes no more discomfort than a traditional vaginal exam, Simpson says. A disposable sensor connected to a cable is inserted through the birth canal after rupture of the amniotic membranes ("breaking of water"), and rests against the baby's cheek, temple, or forehead, pressing up against the uterine wall. Using red and infrared light, the sensor analyzes the fetus' blood oxygen level, and this information is displayed on a monitor, providing real-time data to the OB team.
With the oxygen monitor, Schuler was able to avoid the scalpel and vaginally deliver a healthy baby girl.
"It was kind of scary, because in five minutes they had me numbed up and the operating room ready to go," Schuler says. "But it turned out the baby was fine, which was great because no one wants to get a C-section if you don't have to."
The percentage of C-sections recently has been rising after a steady decline from 1989 to 1995. About 22% of live births in 1999 were delivered by C-section, a 4% increase from 1998, the CDC reports. What's more, the rehospitalization rate after C-sections was 80% compared to the 30% of those rehospitalized following an uncomplicated vaginal birth. In general, women who undergo C-sections risk infections of the uterus or around the incision, as well as urinary and gallbladder complications.
Of the 6,800 babies born annually at St. John's, about 23% are delivered by C-section. Simpson says she is hopeful that the oxygen monitor will reduce that.
A clinical study of more than 1,000 births at nine sites nationwide suggested that fetal oxygen monitors, when used in conjunction with heart rate monitors, could halve the number of C-sections related to a "nonreassuring" heart rate. But the study, published in the November 2000 issue of the American Journal of Obstetrics and Gynecology, also found an increase in the overall number of cesarean deliveries due to dystocia -- failure of the baby to pass through the pelvis. The company that makes the monitors and which funded the study, St. Louis-based Mallinckrodt Inc., is paying for further research to determine what effect the monitors might be having, if any, on women who encounter such difficulties. "It's a very puzzling finding from the study," says Garite, a co-author of the study. "We are doing a follow-up, multicenter study to look at the question."
Researchers also are examining whether the oxygen monitors could be useful in evaluating premature infants, Garite says. Currently, the monitor is employed only in women dilated past two centimeters whose water has broken after a fetal heart monitor shows an abnormal rate. Women who are carrying more than one fetus, who are less than 36 weeks pregnant, or who are carrying a breech baby cannot use the device.
Mallinckrodt declined to disclose the number of hospitals using OxiFirst, but says more and more are adopting the system. At the time of FDA approval, the fetal oxygen monitor had been relied on in more than 35,000 births. The technology has been available in Europe since 1996 and in Canada since 1998.
Garite says he envisions every hospital eventually making use of the technology, which could improve what he considers the often overly intense circumstances under which babies are born.
"We are unnecessarily scaring our moms," Garite says. "When they see us looking at the [heart rate] monitor and becoming concerned and putting oxygen on their faces, they put two and two together. That kind of unnecessary intervention increases the whole anxiety level. As people begin to realize with this monitor that actual hypoxia is so much less frequent, the whole environment will improve."
Kimberly Sanchez is a freelance writer in St. Louis and a frequent contributor to WebMD. She also has written for the Los Angeles Times, New York Newsday, the Chicago Sun-Times, and the Dallas Morning News.