Congenital Anomalies
Neural Tube Defects (NTDs)
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At 4 to 6 weeks, the embryo forms the neural tube and then it closes. Later, the neural tube becomes the spinal cord and brain. An NTD occurs when the neural tube fails to close properly which leaves the developing brain or spinal cord exposed to amniotic fluid.
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Two of the most common birth defects that occur in the first four weeks of pregnancy are spina bifida
and anencephaly.
Spina bifida
Occurs when the lower end of the neural tube fails to close. Thus, the spinal cord and backbones do not develop properly. Sometimes, a sac of fluid protrudes through an opening in the back, and a portion of the spinal cord is often contained in this sac. Paralysis of the infant's legs, loss of bowel and bladder control, water on the brain (hydrocephalus), and learning disabilities are among the disabilities associated with spina bifida. Eighty to ninety percent of infants born with spina bifida live. Despite varying degrees of disability, many lead successful and productive lives.
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Types of spina bifida
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Spina bifida occulta is the most common form. There is a defect in formation of one or more vertebrae. A layer of skin covers the defective area and it is often found incidentally. This form very rarely causes any symptoms or disabilities.
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Meningocele is characterized by a sac protruding through the defect in the vertebral column. The sac includes cerebrospinal fluid, but not neural tissue. It may or may not be covered with skin or with meninges. Patients may have minor symptoms.
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Myelomeningocele is a condition in which a segment of the spinal cord or nerves is exposed in a sac through the defective area of the vertebral column. It may or may not be covered by the meninges. Most patients with this condition have other problems.
Anencephaly
A fatal condition in which the upper end of the neural tube fails to close. In these cases, the brain either never completely develops or is totally absent. Pregnancies affected by anencephaly often result in miscarriages. Infants who are born alive usually die very soon after birth.
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