The study by John Gilmore, M.D., of the University of North Carolina School of Medicine, and colleagues used magnetic resonance imaging. MRI did not show signs of bleeding for babies born by caesarian delivery, they reported in the February issue of Radiology.

    "Small bleeds in and around the brain are very common in infants who are born vaginally," Dr. Gilmore said. "It seems that a normal vaginal birth can cause these small bleeds."

    Gilmore said although more research is needed on the implications of the hemorrhages, vaginal birth has not suddenly become unduly risky.

    "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."

    Gilmore and colleagues said intracranial hemorrhage in full-term infants is usually associated with symptoms such as apnea, bradycardia and seizures. A variety of factors has been suggested to account for the bleeding, including prolonged labor and assisted delivery.

    But for this study, the researchers studied 88 asymptomatic newborns, evenly divided between male and female, of whom 65 were delivered vaginally and the remainder by caesarian.

    The babies were studied using a 3-Tesla MR machine, without anesthetic, between the ages of one and five weeks, the researchers said.

    Seventeen of the babies -- or 26 percent -- had bleeding, including 16 subdural, two subarachnoid, one intraventricular, and six parenchymal hemorrhages.  Seven infants had two or more types of bleeding.
None of the infants with bleeding had been delivered by C-section.

    Intracranial bleeding was significantly associated with vaginal birth, but not with prolonged duration of labor or with traumatic or assisted vaginal birth.

    Typically, such small hemorrhages resolve over time without causing problems, the researchers said, although larger events may cause such issues as seizures, learning disabilities, or problems with motor development.

    The author noted several limitations of the study which may have led to underestimates of the frequency of bleeding.

    "The images were not obtained immediately after birth but in weeks one to five after birth, and, perhaps, we missed cases of intracerebral hemorrhage that had resolved. Also, our imaging protocol did not include T2-weighted or magnetic susceptibility-weighted images, which might be even more sensitive for depiction of hemorrhage."

    They also pointed out that "no follow-up images were obtained to determine imaging resolution of hemorrhage, and no clinical follow-up was performed after the identification of intracerebral hemorrhage."

    "We just don't know at this time what these bleeds may mean over the long term," Gilmore said. "Ultimately, we hope to be able to determine whether intracerebral hemorrhage is associated with later neurodevelopmental problems."

    The group plans to follow this cohort longitudinally to see whether the perinatal bleeding is associated with future difficulties, such as idiopathic epilepsy.

    The research was support by grants from the National Institute of Mental Health and the University of North Carolina School of Medicine. The researchers said they had no financial conflicts.

    (Agencies)