"Fetal heart monitoring is the primary way doctors have tried to identify babies who may later be diagnosed with brain injury," said Janyne Althaus, M.D., a perinatology fellow at Johns Hopkins. "If the fetal monitoring that we currently have doesn't help us identify those babies who are later diagnosed with these brain lesions, then we need to explore other options."
During labor, if a fetus has difficulty getting an adequate supply of oxygen from the mother's blood supply, white matter brain injury can occur. White matter is located in the border zones between the ends of major blood vessels, an area that is very sensitive to cerebral blood flow. Doctors think that less than 10 percent of cerebral palsy cases are caused by this so-called hypoxic-ischemic encephalopathy.
For some years, doctors have thought they would be able to tell when a baby was about to undergo this type of brain injury by electronically monitoring fetal heart rate. "Doctors assumed that they could decrease cerebral palsy incidence by intervening when they identified babies in trouble," Althaus said.
Because the incidence of CP has not gone down in 40 years, Hopkins researchers decided to take a close look at this monitoring system to see if it was doing its job. They searched through a database of infants born between June 1999 and September 2001, and identified 40 babies who were born with white matter brain injury. They then matched those infants with 40 babies who were delivered at the exact same gestational age and in the same manner. All babies were born at Hopkins between the ages of 23 and 34 weeks.
The researchers then scrutinized fetal heart monitoring data to see if they could detect any differences that would have warned of impending brain injury. The researchers did not find any signs from the last hour of the first stage of labor in vaginal deliveries or the hour prior to delivery in cesarean deliveries.
"We may need to go back to the drawing board," Althaus said.
Other Hopkins collaborators on the study include Scott Petersen, M.D.; Harold Fox, M.D.; Cynthia Holcroft, M.D.; and Ernie Graham, M.D.