Most irregularities are “false alarms,” and more precise measures are needed, researchers say

Researchers at Johns Hopkins have added to evidence that continuous electronic fetal heart rate monitoring, widely used during maternal labor, has so many false positive readings that it is unable to reliably identify fetal brain injury caused by oxygen deficiency. Results of the new study by a team at the Johns Hopkins University School of Medicine appeared in the September issue of Obstetrics & Gynecology, the official publication of the American College of Obstetricians and Gynecologists popularly known as “The Green Journal.”

“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, M.D., associate professor of gynecology and obstetrics at Johns Hopkins. “During the last hour of labor prior to delivery, we see many abnormal patterns in the fetal heart rate, but the vast majority of the babies are born normal.”

“Our current standard of care is to monitor the fetal heart rate during labor, but we need a more precise method to identify term babies that are born with hypoxic brain injury,” he says.

For the study, 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 at The Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center between 2007 and 2013. The investigators found some differences in the fetal heart rate tracings between the groups but report that those differences were not enough to distinguish damaged babies from normal ones. Previous studies have shown that continuous heart rate monitoring is not sensitive enough to definitively pick up specific kinds of brain damage, and the Johns Hopkins research adds further support for the need for more precise detection tools, Graham says.

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.

The monitoring aims 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, however, that his study affirms that electronic fetal monitoring appears not sensitive or specific enough to identify the rare cases of brain injury. He hopes his study leads to the development of new technologies for intrapartum fetal monitoring.

“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,” he says. “We need a more precise tool.”

Co-authors are Rebecca R. Adami of The Johns Hopkins Hospital, Stephanie L. McKenney of the Johns Hopkins University School of Medicine, Jacky M. Jennings of the Johns Hopkins Bloomberg School of Public Health, Irina Burd of the Johns Hopkins University School of Medicine and Frank Witter of the Johns Hopkins University School of Medicine.

The research was conducted internally. Burd is the recipient of a National Institutes of Health Career Development Award.

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