Many fetal organs become fully developed during the first or early second trimester of a woman's pregnancy. The brain, however, begins to develop in the third week of pregnancy and continues developing throughout pregnancy and after birth. Because the brain is relatively immature at birth, it is more susceptible to injury from prematurity than other body organs. It is, therefore, routine to examine a premature baby's brain with ultrasound soon after birth.
Intraventricular Hemorrhage (IVH)
The most common and most feared problem in the brain of an extremely premature baby is intraventricular hemorrhage (bleeding that occurs in or around the cavities, or ventricles, of the brain). Bleeding can occur when fragile blood vessels in the brain rupture in the setting of changes in the baby's blood pressure or blood oxygen level. Blood can collect in the area of fragile blood vessels, an area of the brain called the subependymal germinal matrix; it can also spread to the ventricles of the brain or into the brain tissue itself.
Intraventricular hemorrhage is often graded from one through four, according to severity. Grade I, the least severe, refers to a small amount of blood in the subependymal germinal matrix area. In grade II, the blood has spread to the ventricles; in grade III, the pressure from the blood has caused the ventricles to become enlarged; and in grade IV, the most serious, the bleeding has spread into surrounding brain tissue.
Infants who have grade III and IV intraventricular hemorrhage are at increased risk for:
- hydrocephalus. When blood collects in the brain, it can block the flow of cerebrospinal fluid (CSF), the fluid that flows up and down the spinal column and into the brain. When blocked, the CSF builds up and the pressure causes the baby's head to enlarge. To drain off the excess fluid, doctors can perform daily spinal taps. If the hydrocephalus persists or worsens, a surgical procedure called a subgaleal or aventriculoperitoneal shunt may be needed.
- cerebral palsy.
Cerebral palsy is a neurological condition affecting motor power and coordination and is related to damage to the brain early in life. What causes the damage to the motor part of the brain is not completely known. It was long thought that trauma or lack of oxygen during delivery were the main causes, but doctors now think that most of the injury leading to cerebral palsy, especially among full term infants, occurs before birth. Recent evidence has suggested that infection and the baby's inflammatory response to infection may be associated with cerebral palsy in former premature infants, but further studies are needed in this field.
Premature babies are at greater risk for cerebral palsy than full-term babies, though doctors don't know exactly why. Premature babies who have intraventricular hemorrhage or periventricular leukomalacia (a condition in which the white matter surrounding the ventricles in the brain is injured) have the greatest risk of developing cerebral palsy.