Neural Tube Defects - NTDs Introduction Neural tube defects are also known as NTDs. They happen when the spine and brain do not fully develop while the fetus is forming in the uterus. Worldwide, there are more than 300,000 babies born with NTDs each year. Getting enough folic acid, a type of vitamin B, before and during pregnancy prevents most neural tube defects. Treatments vary depending on the type of defect. This reference summary explains what neural tube defects are. It also discusses common NTDs and prevention. What Are Neural Tube Defects? Birth defects of the brain and spine happen during the first few weeks of pregnancy. The neural tube is the structure that eventually develops into the brain and spinal cord. It starts out as a small band of tissue. By 28 days into the pregnancy, the band of tissue folds inward and forms a tube. If the tube does not close completely, it can cause neural tube defects. There are many different types of NTDs. NTDs can cause problems with the: Brain. Skull. Spinal cord. Vertebrae, which are the small bones of the spine. 1
NTDs can be mild or severe. Some can cause death. The most common NTDs are spina bifida and anencephaly. These types are discussed in the following sections. Spina Bifida Spina bifida is a common, potentially disabling birth defect. It affects the spinal column while the fetus is forming in the womb. Spina bifida happens if the fetal spinal column does not close completely during the first month of pregnancy. This may cause some paralysis of the legs. Most infants with open spina bifida are born with an open wound in their back connecting the spine and spinal cord to the outside. This can be repaired surgically, but often the nerve damage is permanent. Closed spina bifida is when there is no open wound but there may be missing or damaged vertebrae in the spinal column. This may also be associated with nerve damage. Depending on the severity of the case, some patients may have no symptoms whatsoever. Many people with spina bifida will need devices such as braces, crutches or wheelchairs to help them move. They may also have learning difficulties, urinary and bowel problems or hydrocephalus. Hydrocephalus is a buildup of fluid in the brain. Often a shunt must be surgically placed to drain the fluid from the brain. There are also milder forms of spina bifida. Children with mild forms may develop normally. There is no cure for open spina bifida. Treatments focus on the complications caused by the defect. Treatments for spina bifida may include surgery, medicine and physical therapy. Ongoing Hydrocephalus therapy, medical care and surgical treatment may be needed to prevent and manage complications throughout life. With proper treatment and care, most children with spina bifida live well into adulthood. Anencephaly Anencephaly is a more serious type of NTD. In this condition, much of the brain and skull do not develop. Anencephaly happens if the upper part of the neural tube does not close all the way. This often results in a baby being born without the front part of the brain. The remaining parts of the brain are often not covered by bone or skin. 2
Babies with anencephaly often have other defects of the head and face. They often have defects in other organ systems, such as the heart. Girls are much more likely than boys to develop anencephaly. Almost all babies born with anencephaly either die shortly after birth or are stillborn. Stillborn means a baby dies in the womb before birth, but after 20 weeks of pregnancy. Causes & Risks The cause of NTDs is not known. Environmental and genetic factors may play a part. But about 95% of babies with NTDs are born to families without a history of these disorders. Some women may be at an increased risk of having a baby with an NTD. For example, if the mother has a condition such as diabetes or obesity, there is an increased risk of NTDs. Women who use specific seizure medications, like valproic acid, may also be at an increased risk of having a baby with an NTD. NTDs also happen more often in some ethnic groups. Hispanics have the highest risk in North America, followed by Caucasians. Talk to your health care provider to learn more about which ethnic groups are at higher risk of NTDs. The risk of having a baby with an NTD cannot be eliminated. But women can reduce the risk by getting enough folic acid before and during pregnancy. Diagnosis In most cases, NTDs can be diagnosed during pregnancy. Screening tests, or prenatal tests, are used to check for NTDs. An ultrasound done around 18 to 20 weeks into pregnancy can show almost all NTDs. An ultrasound uses sound waves to create a picture of the baby and its internal organs. This test is a normal part of prenatal care. Testing a sample of the mother s blood can also show if the baby is at risk of NTDs. The Ultrasound blood test measures the levels of different substances in the mother s blood. If the baby is at risk, an ultrasound is done. 3
A special test called an amniocentesis may also be used to see if the baby has certain NTDs. For this test, a small sample of amniotic fluid surrounding the baby in the womb is taken. The fluid is then checked for birth defects and genetic problems. In some cases, NTDs may not be diagnosed until after a baby is born. Some NTDs, such as anencephaly, are immediately seen at birth. Others, like spina bifida, may require imaging tests, such as an x-ray, MRI or CT scan. An MRI uses strong magnets to create images of the inside of the body. A CT scan is an x-ray machine linked to a computer. A CT scan takes a series of detailed pictures of the organs. Prevention The exact cause of NTDs is not known. However, a vitamin called folate, or folic acid, may help. Folic acid is a B vitamin. Our bodies use it to make new cells. Everyone needs folic acid, but it is particularly important for women who can become pregnant. If a woman has enough folic acid in her body before and during pregnancy, it can help prevent some NTDs. Women who are capable of becoming pregnant need 400 micrograms (mcg) of folic acid every day. NTDs happen within the first few weeks of pregnancy, often before a woman finds out she is pregnant. For folic acid to help prevent NTDs, a woman must: Start taking it at least one month before becoming pregnant. Continue taking it throughout the pregnancy. Talk to your health care provider about taking folic acid before you become pregnant. Your health care provider may recommend a different dose or that you start taking it earlier than one month before becoming pregnant. This is especially true if you have already had a baby with an NTD. 4
Summary Neural tube defects, or NTDs, happen when the spine and brain do not develop completely while the fetus is forming in the uterus. Worldwide, there are more than 300,000 babies born with NTDs each year. There are many different types of NTDs. NTDs can cause problems with the: Brain. Skull. Spinal cord. Vertebrae, which are the small bones of the spine. NTDs can be mild or severe. Some can cause death. The two most common NTDs are spina bifida and anencephaly. In most cases, NTDs can be diagnosed during pregnancy. Screening tests, or prenatal tests, are used to check for NTDs. Treatments vary depending on the type of defect. Getting enough folic acid, a type of B vitamin, before and during pregnancy prevents most neural tube defects. 5