Fetal heart monitoring does not identify babies who
are diagnosed with white matter brain injury after birth,
according to a new study by Johns Hopkins researchers. The
study, reported during the Society for Gynecologic
Investigation's meeting March 24 to 27 in Houston, helps
explain why the incidence of cerebral palsy in term infants
has not changed since the 1960s.
"Fetal heart monitoring is the primary way doctors
have tried to identify babies who may later be diagnosed
with brain injury," said Janyne Althaus, 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 Johns 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 are Scott
Petersen, Harold Fox, Cynthia Holcroft and Ernie Graham.
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