If you have been delivered to this world the natural way, you may have experienced at that moment one of the worst hemorrhages in your life.

A research team discovered, using magnetic resonance imaging (MRI), that the brains of one quarter of the babies delivered vaginally soon after birth presented a small amount of bleeding in and around the brains.

"Small bleeds in and around the brain are very common in infants who are born vaginally," said John H. Gilmore, M.D., professor of psychiatry and Vice-Chair for Research and Scientific Affairs at the University of North Carolina School of Medicine in Chapel Hill. "It seems that a normal vaginal birth can cause these small bleeds."

88 infants, 65 delivered vaginally and 23 by cesarean section, all with a normal appearance and aged 1 to 5 weeks, were equally divided between male and female and underwent MRI.

17 (26 %) of the vaginally delivered infants presented intracranial hemorrhages (ICH) (small bleeds in and around the brain), as MRI investigation revealed and 7 infants even had two or more types of ICH.

Previous approaches depicted a lower percentage (about 10 %) of ICH linked to vaginal birth.

ICH was not connected to prolonged labor or traumatic 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 fetal skull bones are not fused together, so they can shift and often overlap each other during vaginal birth, permitting the baby's head to pass through the vagina.

The shifting can put pressure on the brain, making the blood vessels tear and bleed. Most of the bleedings proved to be tiny subdural hematomas (between the brain and the thick membrane that wraps the brain below the skull bones) and many were situated in the occipital lobe or cerebellum, both in the lower back part of the brain.

This type poses no problems, but larger ones can be harmful later on in the child's life, triggering seizures, subtle learning problems or motor problems. "We just don't know at this time what these bleeds may mean over the long term," Dr. Gilmore said.

Dr. Gilmore points that this research should not make parents discard vaginal delivery. "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."