As many as one in four infants experienced bleeding in or
around their brains soon after they were delivered vaginally, according to a
new study published in the February issue of Radiology.
"Small bleeds in and around the brain are very common
in infants who are born vaginally," said John H. Gilmore, M.D., coauthor
of the study at the University of North Carolina School of Medicine in
Chapel Hill.
Gilmore and colleagues suggested that the small bleeds are
likely caused by the shifting of the bones of the skull, but they may not cause
much harm
in most of cases
if any.
For the study, Gilmore and team used magnetic resonance
imaging (MRI) to study the brains of 44 asymptomatic female infants and 44 male
infants between the ages of one and five weeks, 65 born vaginally and 23 by
cesarean section.
MR images showed that 26 percent of the babies delivered
vaginally had so called intracranial hemorrhages (ICH), or small bleeds in and
around the brain.
Seven infants had two
or more types of ICH.
In comparison, none of the infants with bleeding had been
delivered by C-section.
The new findings differ from prior studies which have shown
approximately 10 percent of intracranial hemorrhage was associated with vaginal
birth.
Earlier studies suggest that not all vaginal births
experience the same risk of small bleeds, which may be determined by other risk
factors such as vacuum extraction in addition to the vaginal pressure.
In a study published in the November 2005 issue of British
journal of obstetrics and gynecology, Boo N. Y. and colleagues from Hospital
Univesiti Kebangsaan
Malaysia
reported that vacuum extraction was associated with subaponeurotic hemorrhage.
But, the researchers said the bleeding examined in the
current study was not due to prolonged duration of labor or on traumatic or
assisted vaginal birth.
"In our study, neither the size of the baby or the
baby's head, the length of the labor, nor the use of vacuum or forceps to
assist the delivery caused the bleeds," Dr. Gilmore said.
"The bleeds are probably caused by pressure on the
skull during delivery."
The researchers explained that the bones of the skull in
newborns are not fused, so they can shift and often overlap each other during
vaginal delivery, compressing the brain and causing blood vessels to tear and
bleed.
But in most cases, the bleeding occurred between the brain
and the thick membrane that covers the brain below the skull, the researchers
noted.
They said these small bleeds resolve over time without
causing problems, but large ones may cause problems such as seizure, subtle
learning problem or problem with motor development later in the child's life.
"We just don't know at this time what these bleeds may
mean over the long term," Dr. Gilmore said.
More studies are needed to assess the long-term effects of
ICH in infants. But Dr. Gilmore noted that these findings do not suggest that
expectant parents should opt to abandon vaginal delivery for C-section.
Experts say that C-section has its own problems as
well.
Other than probably harming the
infants, the mothers are more likely to experience a series of physical
problems including
severe
bleeding, blood clots and emergency hysterectomy, longer-lasting and more
severe pain and infection compared to a vaginal birth.
"Obviously, the vast majority of us who were born
vaginally and may have had these types of bleeds are doing just fine," he
said.
"Humans have been born vaginally for a very long time,
and our brains probably evolved to handle vaginal birth without major difficulty."
Source:
"Intracranial Hemorrhage n Asymptomatic Neonates:
Prevalence on MR Images and Relationship to Obstetric and Neonatal Risk
Factors." Collaborating with Dr. Gilmore were Christopher B. Looney, B.S.,
J. Keith Smith, M.D., Ph.D., Lisa H. Merck, M.D., M.P.H., Honor M. Wolfe, M.D.,
Nancy C. Chescheir, M.D., and Robert M. Hamer, Ph.D.
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