Health & Baby

Tests for spina bifida done before birth

During your second trimester, you can have a blood test called the maternal serum triple or quadruple screen to see whether you have a higher-than-normal chance of having a baby with birth defects. This test is used to screen a fetus for certain abnormalities, including neural tube defects. The most common type of neural tube defect is spina bifida. The triple or quadruple screen test does not pose any risk to the fetus.

Pregnancy: Should I Have the Maternal Serum Triple or Quadruple Test?

If the triple or quadruple screen test shows that you have elevated levels of alpha-fetoprotein (AFP), a neural tube defect in the fetus, such as spina bifida, may be suspected. In this case, the following tests usually are done:

• High-resolution fetal ultrasound. This test can help a doctor identify severe cases of spina bifida in a fetus, such as myelomeningocele , in which tissues and nerves are exposed and protrude from the spinal cord. Fetal ultrasound does not always detect abnormalities related to spina bifida, especially in mild cases.
• Amniocentesis. This test usually is done to confirm elevated AFP levels identified by the triple screen test. It also is used to measure levels of acetylcholinesterase (ACH), an enzyme that is found in fetuses that have neural tube defects. You may have amniocentesis without first having an ultrasound or even when an ultrasound appears normal.

Severe spina bifida is strongly suspected when amniocentesis shows high levels of AFP and ACH and when fetal ultrasound results show severe spinal abnormalities.

An early diagnosis of severe spina bifida allows you to make an informed decision about your pregnancy. If you decide to carry the fetus to term, knowing about the defect can help you and your family prepare for your baby's special needs.

Testing for spina bifida after birth

Children who have mild spina bifida may have no physical symptoms. It is often not found until later in life, when the person has a back X-ray for other reasons. It usually does not cause any problems.

Severe spina bifida is usually obvious at birth, because the baby has a noticeable swelling on the back. Many babies with severe spina bifida, especially those with myelomeningocele, have enlarged heads caused by an excess of spinal fluid in the head (hydrocephalus).

After birth, tests to evaluate the extent of the spinal defect may include:

• MRI, which gives a detailed picture of the brain, spinal cord, and related nerves.
• CT scan, in which an X-ray machine rotates around the body to produce a three-dimensional view. This allows a doctor to see deformities or swelling in the brain and spinal cord.

Spina bifida often results in severe curvature of the spine-scoliosis, kyphosis (hunchback), or both. Periodic physical exams of the spine usually are recommended.

Babies with severe spina bifida often have problems related to nerve damage of the spinal cord. This nearly always affects the urinary system . Evaluation to determine the extent of this damage may include a renal ultrasound and cystourethrogram.

Nerve damage may also affect the limbs, especially the legs. During your child's physical exams, the doctor will look for limb deformities, such as clubfoot . The doctor will also observe your child's arm and leg movements.