Birth defects of the brain and spinal cord are called "neural tube defects." These defects occur when the brain and spinal cord do not develop correctly early on in pregnancy. The cause is often unknown.

The brain and spinal cord begin developing in the third week of pregnancy from a flat piece of tissue called the "neural plate". The neural plate forms a long tube which should close to form the brain and spinal cord during the fourth week of pregnancy. After this occurs, the brain continues to develop into its special sections throughout pregnancy. Normally the cells of the brain and spinal cord grow and divide without a problem. However, neural tube defects will occur if this process is altered.

There are two common types of neural tube defects. Both occur most commonly in the lower spine because that is the last area of the neural tube to close during development. The two types are called a meningocele and a myelomeningocele.

A meningocele is a hernia-like protrusion through an opening in the vertebral column over the lower back. This protrusion contains only spinal fluid. A myelomeningocele is a hernia-like protrusion of the neural tube through a defect in the vertebral column. This defect is more serious because the protrusion contains elements of the spinal cord which send and receive messages to and from the lower body. Depending on the extent of the defect, the baby may have varying degrees of paralysis below the level at which the defect occurs.

Hydrocephalus, commonly called "water on the brain," may result from neural tube defects. This is because the brain and spinal cord are surrounded by spinal fluid. The spinal fluid is located in the head in spaces call ventricles. When a neural tube defect occurs, the defect can obstruct the flow of the spinal fluid, which may cause the fluid to build up in the ventricles of the head. Although this may not be readily noticed in the fetus or newborn by the size of the head, we can see the enlarged ventricles through special scanning procedures such as ultrasound.

Babies with neural tube defects will require surgery shortly after birth to close the defect. This helps to prevent infection and preserve as much neurological function as possible. If hydrocephalus has occurred, surgery may also need to be performed to drain the excess spinal fluid that has built up in the ventricles of the head. This is important so that the brain can grow normally.

GASTROSCHISIS

Gastroschisis is an abnormality of the abdominal wall which allows the abdominal contents to fall outside of the body. It does not seem to be hereditary, and the cause is not known. We do know that the problem occurs early in the development when the abdomen is forming.

This abnormality usually occurs just to the right of the umbilical cord. Abdominal contents that may be present outside of the body include:

• Intestines
  
• Stomach
  
• Gall bladder
  
• Uterus
  
• Fallopian tubes
  
• Part of the liver (rarely)

An infant with gastroschisis will require surgery soon after birth to place the contents back into the abdominal cavity. A team of specialists, including a maternal-fetal medicine specialist, a pediatric surgeon and a neonatologist will plan the delivery and care of your baby before and after birth. If possible, you will be able to have a consultation with the pediatric surgeon for a more complete discussion of your baby's diagnosis.

An omphalocele is an abnormality in the abdominal wall which allows the abdominal contents to protrude out from the abdomen.

To understand how this problem occurs, a brief explanation of abdominal development is necessary. During normal early development, the abdominal cavity is too small to accommodate the intestines and, therefore, they are normally located in the umbilical cord. After the 10th week of development,  the intestinal contents should return to the abdominal cavity.

An omphalocele occurs when there is failure in the growth of the wall of the abdominal cavity. This interferes with the intestines returning to the abdominal cavity. Therefore, the organs which are normally located within the abdominal cavity remain in the base of the umbilical cord. An omphalocele can vary in size and may contain any or all of the following structures:

• Small and large intestine
  
• Stomach
  
• Liver
  
• Spleen
  
• Bladder
  
• Uterus
  
• Ovaries

A baby's kidneys become functional at about 14 weeks gestation. The kidneys filter waste from the blood, regulate the concentration of chemicals in the blood and extracellular fluid, and remove excess water from the body. The liquid waste from the kidneys, urine, passes to the bladder through the ureters. The bladder stores the urine. The urine is released from the body by a narrow tube from the bladder called the urethra.

• Hydronephrosis is distention of portions of the kidneys by urine that cannot flow past a blockage in the ureter. This causes backflow and distention of the kidney.
  
  
• Vesicoureteral reflux is abnormal backflow of urine from the bladder to the ureter resulting from a congenital defect-abnormal placement of the ureter on the bladder or obstruction of the outlet of the bladder.
  
  
• Cystic kidneys are kidneys that are enlarged with fluid-filled cavities due to imperfect formation. Therefore, the kidneys are unable to function correctly.
  
  
• Posterior urethral valves usually occur in males and cause an obstruction to the flow of urine.