Causes Of Neural Tube Defects

Michael Bennett
October 10, 2015 - 253 Views

A neural tube defect (NTD) is a type of birth defect that affects the spinal cord and the brain. In our country, some 3,000 babies each year are born with an NTD. The neural tube usually develops into the spinal cord and the brain. In utero, it starts as a flat, tiny ribbon and then slowly develops into a tube. By the end of the first pregnancy month, the tube is fully formed. However, in some pregnancies, the tube doesn’t close properly and this can lead to an NTD. An NTD is a serious medical condition that can lead to death.

If a woman who is trying to get pregnant takes folic acid (400 micro-grams) daily before she attempts to get pregnant and up to the first month of pregnancy, the risk of her unborn baby developing an NTD is significantly reduced. Folic acid, a type of B vitamin, is needed by every cell in the body in order to promote normal development and growth.

A number of NTDs can be found in babies:

Spina bifida
Anencephaly
Encephalocele
Hydrocephalus

What Is Spina Bifida?

Out of the various NTDs, spina bifida is the most common. Around 1,500 babies are born with it in this country each year. In a body with spina bifida, the tiny vertebrae bones don’t completely close, which means that some of the spinal cord actually pokes through the person’s spine. Sometimes, surgery can be used before or after birth to treat spina bifida. However, it is not uncommon for children with this NTD to have problems controlling their bowel movements and bladder and to have paralyzed legs. Spina bifida can also be reasonably mild, in which case it also causes fewer problems.

What Is Anencephaly?

This is the most severe of all neural tube defects. Around 1,000 children are born with this condition in this country each year. These children are lacking major parts of their scalp, skull and brain. Usually, babies only survive for a few hours after birth. The condition occurs when the neural tube that goes on to form the brain doesn’t completely close. In most cases, a child born with this condition will also have other birth defects to the face and head and other parts of the body. It has been observed that it is three times more common for anencephaly to occur in girls than in boys.

What Is Encephalocele?

Encephalocele is the rarest of the four common NTDs. It affects the skull and the brain. In this country, some 375 babies are born with the condition each year. The membranes that cover the brain are normally contained within a sac, but in someone with encephalocele, the sac pokes through an opening somewhere in the skull. Often, a part of the brain also pokes through. While it can happen at any part of the skull, it is most common in:

• The base of the skull, at the point where the neck and skull come together. This is the most common place for encephalocele to develop.
• Between the nose and the forehead.
• In the middle of the skull’s top part.

A baby born with encephalocele will usually require surgery to ensure that the parts of the brain that poke out are placed inside the skull. The opening is then closed. This surgery is reasonably successful, although complications may occur. The outlook for these children varies, depending mainly on where the opening is and which parts of the brain have been affected. Additionally, many of these children have other birth defects as well, which can complicate the situation. The birth defects often affect the head and face. Twenty percent of children born with encephalocele are still born, which means that they died in the womb after the 20th week of pregnancy. Children who do survive often have lasting disabilities, such as:

• Learning disabilities, which are present in around 75% of cases. As such, only around 25% have “normal” intelligence.
• Physical disabilities affecting movement in particular, with some children being paralyzed
• Problems with vision, including blindness
• Seizures

What Is Hydrocephalus?

Hydrocephalus is a form of fluid build up in the brain. Babies who are born with hydrocephalus will be offered surgery, where a shunt (a type of tube) is inserted into the brain. The excess fluid in the brain is drained through the shunt, which runs just underneath the skin and leads to either the abdomen or the chest. The fluid then passes directly into the body, and it is not harmful to overall health.

What Causes Neural Tube Defects?

Unfortunately, it isn’t entirely clear as to what are the causes of NTDs. A number of possible causes include:

• Genetics, whereby a condition is inherited from one of the parents. As parents pass on a variety of traits to their children, including hair and eye color, they can also pass on birth defects, which can be present in their genes.
• Environment. Unfortunately, we live on a heavily polluted planet, which means that it is possible to come into contact with various toxins and chemicals that can be harmful, particularly to unborn children. These include cigarette smoke and lead exposure, for instance.

Who Could Have a Baby with an NTD?

Anyone could have a baby that has an NTD, even if they do take folic acid before and during pregnancy. However, some people are at higher risk. These include:

• Couples where there is a family history of or genetic link to NTDs. If, for instance, you or someone in your family has had a baby with an NTD, the chance of you having one is larger. In fact, if you have had a baby with an NTD, the chance of a subsequent child also having one is 4%. While that is still relatively low, it is a huge increase compared to people who do not have a history of NTDs. If you have had two children with an NTD, the chance of having a third one with an NTD as well is as high as 10%. This is why it is vital that couples who have experienced neural tube defects are treated by a genetic counselor to discuss the risks and possible options.

• Women who take certain medication against seizures. Any woman who takes anti-seizure medication should first speak to a health professional about pregnancy. Data is available in terms of which medication carries a higher risk of NTDs, and a health care professional will be able to advise you on that.

• Women who are obese. A number of independent studies have now shown that obesity carries an increased risk of NTD development. This is why it is important to be at a healthy weight before becoming pregnant.

• Women with diabetes. Diabetes, both type 1 and type 2, are believed to increase the chances of having babies with an NTD. It is possible that this is due to the elevated levels of glucose in the blood.

• Being of a certain ethnicity. Statistics have shown that Hispanic people have the greatest chance of having a baby with an NTD, followed by Caucasians. They are the least common among Ashkenazi Jews, African Americans and the majority of Asians.

How to Prevent NTDs

One of the most important and easiest ways to prevent an NTD is by taking folic acid, the B vitamin. It is vital that a woman’s body has sufficiently high levels of folic acid before they fall pregnant and during the first month of pregnancy. Once the neural tube has closed, they no longer have to take folic acid supplementation.

It is recommended that women of childbearing age take daily multivitamins and that these should contain at least 400 micro-grams of folic acid. They should take this whether they are trying to get pregnant or not. Those who want to get pregnant or who are already pregnant and in the first month could take up to 1,000 micrograms of folic acid daily. It is not recommended to take more than 1,000 micrograms unless specifically told to do so by a physician.

It is also vital that women continue to take folic acid during their first month of pregnancy. They can do this by continuing to take the multivitamin supplement, but they must increase their folic acid intake to at least 600 micrograms per day. Again, it should not exceed 1,000 micrograms, unless specifically told to do so by a physician.

Women who have already had a pregnancy resulting in an NTD, or who are otherwise at greater risk, will generally be told to take more folic acid. Usually, this will be as much as 4,000 micrograms per day, from one month before starting to try to become pregnant to the end of the first month of pregnancy. Studies have shown that doing this can reduce the chances of having a baby with a neural tube defect by as much as 70%. Taking 4,000 micrograms of folic acid is also recommended for women with seizure disorders, diabetes or spina bifida. Because these levels are so high, it is recommended to consult with a physician on how to take such amounts.

Folic Acid and Food

It is possible to get folic acid from your diet as well. A number of flour products, as well as pasta, cereals and breads, may contain folic acid. Search for products like these that specifically say they have been fortified or enriched with folic acid. Certain corn products, like corn meal and tortillas, are no longer fortified, although it is possible that some manufacturers will return to adding folic acid to them. Certain fruits and vegetables also have folic acid in them. In its natural form, folic acid is called ‘folate’. Folate can be found in leafy green vegetables, beans and orange juice. However, in order to reach the right levels of folic acid, you will need to eat a lot of them every day. This is why it is recommended to still supplement your diet with folic acid or a multivitamin.

Is It Possible to Detect an NTD Before Birth?

As medical science improves, a number of different pregnancy screening tests have been devised that allow NTDs to be identified before birth. Most women are offered these tests routinely, although it is up to them whether or not they accept them. Those who are at increased risk of having children with a neural tube defect will be strongly encouraged to take these tests. The screening tests available at the moment are:

The quad screen, which is a simple blood test. It measures four specific substances that will tell medical professionals whether the chance of an NTD being present is high or not. It does not, however, give details about possible encephalocele.
The ultrasound scan, whereby physical deformities can be picked up. Most women will have an ultrasound at around 18 to 20 weeks pregnancy anyway, which will be able to detect NTDs in 95% of the cases.

If either of these tests show that an NTD may indeed be present, further tests are likely to be recommended. These include more detailed ultrasound and amniocentesis, whereby a sample of amniotic fluid will be tested for chromosomal abnormalities.

Why It Is Advisable to Detect an NTD Before Birth

If a test shows that an NTD is likely to be present, an expectant mother will be able to make decisions as to the next steps to take. These include:

• Giving birth in a hospital with a specialized unit for babies with NTDs, so that they can have the necessary treatment immediately.
• Deciding whether it is better for the baby to be delivered vaginally or through cesarean section.
• Looking into having surgery on the baby while it is still in the womb, which may be offered to babies with spina bifida. Completing this surgery during pregnancy, while the baby is still in the womb, has been shown to be more effective than having the same surgery performed after birth. However, this surgery is not without risks and should be carefully considered.

Additional Resources:

American Academy of Pediatrics Resource on the Importance of Folic Acid
Spina Bifida Association Resource on This NTD
Centers for Disease Control and Prevention Resource on the Effects of Folic Acid
National Institutes of Health Resource on the Causes of NTDs

Michael Bennett

About Michael Bennett

Michael Bennett is Editor-in-Chief of Consumer Protect.com. Since 1999, he's worked across a multitude of areas of consumer protection including defective products, environmental issues, identity theft, predatory lending and more. If you find his articles helpful please share them with your readers.