False positives make fetal heart monitors unreliable

"We were looking for more subtle but definitive changes on the monitor tracings indicative of brain injury to incorporate into our training of young physicians, but we did not find them," says Ernest Graham. "We need a more precise tool." (Credit: iStockphoto)

Used during childbirth, electronic fetal heart monitors don’t reliably warn doctors of possible brain damage from oxygen deficiency, research shows.

The commonly used procedure, often involving a belt or band holding a sensor against the mother’s abdomen, triggers too many false positives to be useful, researchers say.

The study, by a team from the Johns Hopkins University School of Medicine, appears in the journal Obstetrics & Gynecology.

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“Brain injuries caused by oxygen deprivation in newborns are rare, and our study shows that in most cases, irregularities detected by an electronic heart rate monitor are false alarms,” says Ernest Graham, associate professor of gynecology and obstetrics.

“We need a more precise method to identify term babies that are born with hypoxic brain injury.”

The researchers analyzed medical records and monitor readouts for the last hour of labor before delivery of 39 babies with hypoxic-ischemic encephalopathy and 78 babies without such brain injuries. The infants were born at the Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center between 2007 and 2013.

Previous studies showed that continuous heart rate monitoring as currently used is not sensitive enough to definitively pick up specific kinds of brain damage.

A more precise tool

“We were looking for more subtle but definitive changes on the monitor tracings indicative of brain injury to incorporate into our training of young physicians, but we did not find them,” Graham says. “We need a more precise tool.”

Hypoxic-ischemic encephalopathy, characterized by restricted blood flow to the brain, is blamed for 23 percent of neonatal deaths globally, but it occurs at a rate of one to four cases in every 1,000 births. Treating the infant within six hours of birth with whole-body cooling reduces symptoms and mortality.

Monitoring is intended to alert physicians if the fetal brain is deprived of oxygen during labor and delivery. Data show that if the heartbeat slows, it may signal oxygen deprivation. When that happens, the choice is often a rapid cesarean section to limit or prevent any damage from oxygen loss.

Graham says he hopes his study leads to the development of new technologies for intrapartum fetal monitoring.

Source: Johns Hopkins University