Published in Panorama
Folic Acid: Can it Prevent Neural Tube Defects in Babies
The general overall ratio of Neural Tube Defects (NTD) is around 1 to 1.5 per 1000 births and in some countries they claim that it can be as high as 5 per 1000 births. In the USA, almost 2500 babies are born abnormal every year! The incidence of NTD is higher if either parent has got one or they’ve had a sibling with NTD or they’ve got some other member in the family – a third degree relative, who has got it – these tend to increase the chances 5% and recurrence risk may go up to 20% even.
Neural Tube Defects are abnormalities in the development in brain and/or spine of a baby. Basically three groups of conditions, comprise NTD: Anenecephaly, Spina bifida and Encephelocele. Out of this, what hits the maximum is anencephaly and spina bifida, reveals Dr.Janaki Gopalan, Specialist Obstetrician and Gynaecologist, Welcare Hospital, Dubai. Spina bifida is the most frequently occurring permanently disabling birth defect, which results from the failure of the spine to close properly during the first month of pregnancy. In severe cases, the spinal cord protrudes through the back and may be covered by skin or a thin membrane.
Anencephale is a condition in which the whole vault of the head is not there. The baby just comes with popping eyes and the whole forebrain is lost. It can be diagnosed as early as 12 weeks of pregnancy. This is where the expertise factor comes in. Encephalocele results in a hole in the skull through which brain tissue protrudes. These babies also do not live to survive, reveals Dr.Janaki.
What are the factors that cause NTD and who are the women prone to giving birth to babies with NTD? Women who have given birth to a baby with NTD, those who have a close relative who has an NTD, women or their partners who themselves have an NTD, women who are insulin-dependent diabetics, women with epilepsy who are on medication for the problem and obese women are at increased risk of giving birth to babies with NTDs.
In respect of the contributory factors, there exists a strong correlation between folic acid deficiency and NTDs, reveals Dr.Janaki. “Incidence of NTDs are known to decrease by as much as 50% - 70% with sufficient intake of folic acid, well before pregnancy and continuing it for up to at least 12 weeks of pregnancy. NTDs are possibly thought to be more common in the socio-economically deprived where they are not eating too well, where generally the folic acid fortification is not there. In developed parts of the world they have realized this and much of work has been put into fortifying foods with folic acid – from bread flour to cereals. What is important is that folic acid should go well before pregnancy is planned.”
Though Folic acid is present in green leafy vegetables, its consumption in this form is not sufficient fortification. Hence, it is best taken as a supplement in tablet form, emphasizes Dr.Janaki. What is normally recommended is only 400 microgram. Unlike vitamin A and vitamin B, it doesn’t get retained and therefore it can be taken for months together without coming to any harm.
Besides folic acid, environmental pollution and some genetic factor, may also be responsible for NTDs.
When can we diagnose NTD in pregnancy? What all pregnant women are now offered, is an ultrasound scan between 12 – 14 weeks of pregnancy to detect Down’s Syndrome, NTDs, etc. Or, at week 15, they are offered an Alpha fetaprotein (AFP) screening. When the neural tube fails to close, AFP, a fetal substance, leaks into the amniotic fluid and the mother's blood. If the blood test reveals a high AFP level, it most likely indicates that the pregnancy is possibly affected by an NTD. An ultrasound would confirm the diagnosis –of any of the three types of NTDs.
Definitely, if one has had an abnormal child in the family, all these tests can be recommended in them. But to someone who comes out of the blue and you talk to them about these screening tests, they don’t feel they need to have these tests done, says Dr.Janaki. However, often, NTD may only be picked out of the blue, without any risk factor being present. A genetic factor or environment pollution may have been the contributing factor leading to these abnormal fusions of the neural tube.
While the need for screening with a very good quality ultrasound machine may not be overemphasized, it is extremely important that the ultrasound be necessarily carried out by a specialist fetal medical person, trained in doing and interpreting the ultrasound, emphasizes Dr.Janaki. This is more so if the pregnant woman carries a risk factor for abnormal birth. This is more true in the case of spina bifida where diagnosis can be missed, especially in closed spina bifida, reveals Dr.Janaki.
An ultrasound examination involves the whole head of the baby having to be visualized, to see whether the cerebrum is well formed, the cerebellum is normal. Further, the entire spine has to be tracked right up to the end and each vertebrae has to be seen to observe if the fusion factor has occurred. Unless the entire spine, from top to bottom is mapped well, abnormalities may not be excluded. Because, many a times, the skin will be fused on the top and the fat underneath the skin is where you get the deformity because the vertebrae are not fused properly, explains Dr.Janaki.
But there are instances of children growing into adulthood, carrying out every normal activity, without knowing they have spina bifida. Is this true? Yes. This is what we call as spina bifida occulta where you don’t find anything except a thin tuft of hair in the spine region. Later on, at some point if they have any urinary problem or when an X Ray of the spine is taken for some other reason, it may get diagnosed. This is spina bifida which takes a lot of expertise to pick it up during the pregnancy. But per se, this form of spina bifida causes no problem at all.
What is the treatment for NTDs? There are places in America where, when they find out these abnormalities, they do the shunting when the baby is in the uterus itself so that it doesn’t cause a lasting damage. At least 20 weeks, it is saved. But eventually, what happens is only after the baby is born and when it grows, you can assess the gross level of deformity. In the case of spina bifida, Surgery to close a newborn's back is generally performed within 24 hours after birth to minimise the risk of infection and to preserve existing function in the spinal cord.
What is the prognosis for babies born with NTDs? When you offer treatment for these conditions, it is very difficult to offer a prognosis on, which baby may have a better quality of life but then who will be completely abnormal, responds Dr.Janaki. The problem is, spina bifida babies may come out with paralysis. Either both the legs go paralysed, they may have fetal incontinence, urinary incontinence, which can all be corrected. What would be the quality of the life that the child gets, is a very individual feature depending on the surgery done, on how severe the lesion was, what was the extent of the compromise. Some of them do completely well after surgery, but in some cases, a residual paralysis can be there. And this will be a persistent lifelong disability. It will never cause a trauma to the life; that is longevity of life will be there, but at an impaired quality. Spina bifida may be associated with other abnormalities involving the kidney and the children could also have neurological impairment. Physical and mental growth may be affected to varying degrees depending on the severity of the factors involved. Subnormal intelligence may also be associated with the condition.
Is it true that some children with spina bifida can also have hydrocephalus, which is fluid accumulation in the brain? While spina bifida is an entity by itself, it can be associated with hydrocephales, clarifies Dr.Janaki. “Sometimes you do get associated abnormalities. If you develop one abnormality, you can easily have associated Meningocele or myelomeningocele or hydrocephalus. That is why, when you pick up one abnormality, it should have a complete survey of the whole neurological system and often, a single scan may not give you an answer. You may need serial scans to see whether hydrocephalus is developing. Hydrocephalus can also be associated with spina bifida and you may need correction for the spina bifida and the hydrocephalus to be shunted to drain the brain. The severity of the hydrocephalus will tell us the extent of mental impairment of the child.
To what extent can NTDs be prevented? It is known that 50-70% of NTDs can be prevented through the consumption of 400 micrograms of folic acid per day, in the case of women with no risk factors. Women with high risk are advised 5 milligrams of folic acid supplements everyday much prior to conception and also through the first trimester of pregnancy, at least, emphasizes Dr.Janaki.