Genetics Northern California

Spina Bifida

Spina bifida is the most common permanently disabling birth defect. Approximately 3,000 pregnancies per year are affected by spina bifida in the United States - more than muscular dystrophy and cystic fibrosis combined. Spina bifida affects approximately 7 out of every 10,000 newborns in the United States.

Spina bifida is a general term used to refer to spinal cord malformations. Spina bifida is part of a group of birth defects called neural tube defects or myelodysplasia. Other forms of neural tube defects include anencephaly and encephalocele. Neural tube defects occur when the brain and spinal column fail to form normally in the first month of pregnancy. The most severe form of spina bifida is called myelomeningocele. In this condition, a sac consisting of meninges (the spinal cord's protective covering) and portions of the spinal cord protrude through an opening in the defective vertebral column. The sac may also protrude through the skin, leaving the cord unprotected. Surgery to close the baby's back is usually done within the first 24 to 48 hours of life to protect the spinal cord and nerves from trauma, to guard against further loss of functional ability, and to prevent infection.

Spina bifida usually results in multiple medical problems as a result of spinal cord damage. The extent of medical problems is usually related to where the spinal cord lesion is located. Related problems can include lower extremity (feet and legs) paralysis, problems with bowel and bladder control, accumulation of fluid in the brain (hydrocephalus), learning disabilities, and latex allergy. These medical issues often require extensive follow-up and surgery.

Spina bifida can happen in any pregnancy. In fact, 95% of women who have a spina bifida-affected pregnancy have no family history of the condition. In most cases, spina bifida is caused by a combination of environmental factors during pregnancy and the unique genetic make-up of the individual. This is also called multifactorial inheritance because it involves many different contributing factors, both genetic and environmental.  Usually the exact combination of factors involved is unknown. A few specific risk factors are known to increase the chance for neural tube defects. These risk factors include a family history of a neural tube defect, prenatal exposure to certain medications (e.g.,Tegretol, Depakote, Trileptal), and poorly-controlled diabetes prior to pregnancy.

Less often, spina bifida is part of a genetic syndrome caused by a change in the genetic instructions. In this circumstance, the person with spina bifida may have other birth defects or developmental delays due to the syndrome.

Research studies indicate that more than half of all neural tube defects could be prevented by taking 0.4 mg of folic acid (a B vitamin) before conception and during the first three months of pregnancy. It is now recommended that all women of child-bearing age (between 15 and 45) should consume 0.4 mg of folic acid daily, even when they aren't actively trying to become pregnant. 

Fertility is normal in women with spina bifida, while many men with this condition are infertile. Women with spina bifida should have the same success in becoming pregnant as women without spina bifida. There are sometimes problems that develop during pregnancy and delivery in women with spina bifida. Although there are few obstetricians with specific experience in working with these women, a caring, interested doctor can work closely with them to provide appropriate care. Men with spina bifida may be infertile, but they can often have erections. Testing can be done to determine if a man has an adequate number of active sperm. A man's urologist can work with him to discuss relevant tests and reproductive options.

Recurrence risk
A woman who has had one baby with spina bifida is more likely to have subsequent affected pregnancies. There is also an increased chance for spina bifida in any child of a parent who has spina bifida. In both situations, the chance for spina bifida is estimated to be about 3% for each pregnancy. Research shows that women who have had a previous pregnancy with spina bifida or women who themselves have spina bifida can significantly reduce their risk of in any future pregnancy by taking a folic acid supplement. The Center for Disease Control (CDC) recommends a dose of 4 mg daily, starting at least one month prior to any planned pregnancy and continuing through the first three months of pregnancy. A genetic counselor can meet with you to discuss recurrence risks and prevention strategies for the parent with spina bifida, a couple who has already had a child with spina bifida, and for relatives of the parents or child.

Prenatal Diagnosis 
Most babies with spina bifida can be detected during pregnancy. The California Prenatal Screening Program helps to finds pregnancies that are at increased risk for several different types of birth defects, including spina bifida. Part of the test includes a blood sample taken between 15-20 weeks in the pregnancy. Testing includes the measurement of a protein called alpha fetoprotein (AFP). AFP is made by the fetus, and is normally present in a pregnant woman's blood. Abnormally high amounts of AFP in the mother's blood means that the pregnancy is at increased risk for a neural tube defect (NTD) such as spina bifida. This simple screening test can detect about 80-95% of pregnancies with a neural tube defect (including anencephaly), but it is not foolproof.

If the AFP blood level is abnormal, further testing is offered, including a detailed ultrasound exam. Most neural tube defects can be seen during pregnancy with a detailed ultrasound, however, sometimes the defect may be difficult to see because of the baby's position or the location or size of the lesion.

AFP can also be measured in the fluid surrounding the fetus, by a procedure called amniocentesis. In addition to examing the developing baby's chromosomes, the AFP level in the amniotic fluid is able to help identify neural tube defects. Amniocentesis, carries a small risk of miscarriage (less than 1 in 300).

The Kaiser Permanente Regional Spina Bifida Clinic was created in 1986 to provide well-coordinated state-of-the-art care for persons diagnosed with a neural tube defect, such as spina bifida. Today the clinic actively follows approximately 200 children and adults from throughout northern California, currently ranging in age from newborn to 70 years old. Because spina bifida was historically just a pediatric condition, most spina bifida programs were established at pediatric hospitals, and so do not treat adults. Kaiser Permanente's Regional Spina Bifida Clinic (SBC) is one of the few nationwide that does.

Individuals with spina bifida usually have complex medical needs that require coordinated care for multiple systems, including:

central nervous system (brain and spinal cord)
genitourinary (bladder, kidney)
gastrointestinal (colon)
musculoskeletal (spine and lower extremities).

These individuals may also experience multiple developmental and psychosocial issues. For this reason, the SBC includes a clinic team consisting of care providers from a wide range of disciplines.