Doctors are not certain what causes spina bifida, or why neural tubes do not develop or close properly in some babies, though they have identified a few risk factors for spina bifida. Risk factors include race, gender, family history, folic acid deficiency, diabetes, obesity and increased body temperature in the early months of pregnancy.
What is Spina Bifida?
Spina bifida is a serious birth defect that occurs when the tissue surrounding the developing spinal cord of a fetus does not close properly during the first month of pregnancy. It is part of a group of birth defects called neural tube defects, a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings.
In babies with spina bifida, a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones of the backbone. Infants born with spina bifida sometimes have an open lesion on their spine where significant damage to the nerves and spinal cord has occurred. Although the spinal opening can be surgically repaired shortly after birth, the nerve damage is permanent, resulting in varying degrees of paralysis of the lower limbs. Even when there is no lesion present there may be improperly formed or missing vertebrae and accompanying nerve damage. In addition to physical and mobility difficulties, most individuals have some form of learning disability. Spina bifida may also cause bowel and bladder complications, and many children with spina bifida have hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain).
The three most common types of spina bifida are:
- Myelomeningocele. The severest form, in which the spinal cord and its protective covering (the meninges) protrude from an opening in the spine.
- Meningocele. The spinal cord develops normally but the meninges protrude from a spinal opening.
- Occulta. The mildest form, in which one or more vertebrae are malformed and covered by a layer of skin.
Spina bifida is one of the more common birth defects in the United States. The incidence of spina bifida can be decrease by up to 70 percent when a daily folic acid supplement is taken prior to conception.
Who Is At Risk For Spina Bifida?
Doctors are not certain what causes spina bifida, or why neural tubes do not develop or close properly in some babies, though they have identified a few risk factors for spina bifida as follows:
- Race. Spina bifida is more common among Hispanics and whites of Northern European descent.
- Gender. More female babies are born with spina bifida.
- Family history. Couples who have had one child with a neural tube defect have a slightly higher chance of having another baby with the same defect. That risk increases if two previous children have been affected by the condition. In addition, a woman who was born with a neural tube defect, or who has a close relative with one, has a greater chance of giving birth to a child with spina bifida. However, most babies with spina bifida are born to parents with no known family history of the condition.
- Folic acid deficiency. This vitamin is important to the healthy development of a fetus. Lack of folic acid (vitamin B-9) increases the risk of spina bifida and other neural tube defects.
- Some medications. Anti-seizure medications, such as valproic acid (Depakene), seem to cause neural tube defects when taken during pregnancy, perhaps because they interfere with the body’s ability to use folic acid.
- Diabetes. The risk of spina bifida increases with diabetes, especially when the mother’s blood sugar is elevated early in her pregnancy. Careful blood sugar control and management can decrease this risk.
- Obesity. There is a link between pre-pregnancy obesity and neural tube birth defects, including spina bifida. Exactly why obese women have an increased risk of having a baby with spina bifida is not known, but is possibly because of nutritional deficits from poor eating habits or because they may have diabetes – another known risk factor for neural tube defects.
- Increased body temperature. Some evidence suggests that increased body temperature (hypothermia) in the early months of pregnancy may increase the risk of spina bifida. Elevating your core body temperature by about 3 to 4 degrees Fahrenheit above normal, due to fever or the use of saunas and hot tubs, can raise body temperature and has been associated with an increased risk of spina bifida.