itself. So, these are the defects that can
arise; neural tube defects and these are actually
quite common as abnormalities go. Perhaps,
0.3% of all pregnancies, three babies per
thousand that may show an identifiable neural
tube defect. How many babies are actually
born alive with a neural tube defect? It depends
upon local laws. It’s relatively easy to
detect on ultrasound scans, you can see that a part
of the neural tube that’s not closed properly.
That then presents parents with a
dilemma, as whether they wish to attempt
the termination of the pregnancy or
to allow the pregnancy to continue,
as we’ll see, there are significant problems
that can arise from a neural tube defect of that kind.
Variety of different versions of it. It may be an open or a closed neural tube defect.
And of course, it may be at different levels.
So it may be at the head-end, more commonly,
turned towards the lower back. If the defect is at the
head end, this condition is called anencephaly.
That means that the fore-brain has
not closed properly. Therefore,
much of the neural structures
of the brain cannot develop.
We will see that it’s largely the brain
that drives the formation of the skull.
That might be surprising. You tend to think of the
skull as being very solid, very well-determined
structure, and the brain is being something
which is relatively soft and pliable.
It’s actually the other way around. There’s the
development of the brain that induces and
drives the development of the skull. Therefore,
if the fore-brain does not close properly,
if there’s a neural tube defect, anencephalic defect
at the head end and so what that means is
that the bony plates of the skull will not form either and there’ll
be a massive opening at the anterior end.
And this will be a massive opening at the back of the baby's head as a result.
As a result of this skull and brain failing to
develop properly, then this condition will
invariably be fatal after birth. It’s just
not something that the baby can survive, but
the baby will survive during its time in the
uterus. As a result, what can sometimes happen
is that if a baby is born with this condition,
one possibility is that that baby might be
used as an organ donor for other babies or
adults who are lacking some important structure,
kidneys, for instance, or heart. But there’s
a very difficult ethical dilemma of allowing
an anencephalic pregnancy to continue to full
term because of course that in turn will pose
some risks for the mother. A
closed defect of the spine
will still have the membranes
covering the spinal cord
and therefore, the damage is less severe as a result.
If it’s open, then there will
be an interruption of the function of the
spinal cord. That can mean in time that when
the baby is born, there may well be severe
nerve problems resulting from that. So, for
instance, you could have paralysis and loss
of function, and that loss of function is
very likely to affect the bladder and bowels,
and of course in the extreme, such a condition
will lead to death. So again, it can be fatal.
At the very minor end, you can have what’s
called spina bifida occulta. That means that
everything has happened fairly normally, but
the vertebrae at the lower part of the spine
have failed to fuse over. So there’s a kind
of opening in the spine itself. A little bit
of the spinal cord is perhaps a little more
exposed than it would be normally. But essentially,
you may not even be aware of that. One odd
consequence is that in spina bifida occulta,
you sometimes get a little patch of hair to
the base of the spine. So that’s something
that you can check for. But spina bifida occulta
is not a defect. It’s merely a variation,
and the chances are, that there will not be
of any clinical significance during the course
of your development if you have this condition.
So the incidence of neural tube defects can
be significantly reduced, perhaps, by up to
70% by giving folic acid beforehand.
Folic acid is a vitamin that is found in some food,
but it’s really hard to eat the amount of
these particular kinds of foods, broccoli,
for instance, to get the amount of folic acid
that you would need. So it’s common to advice
women who are thinking of becoming pregnant
to supplement their diet with folic acid tablets
beforehand. Even if you haven’t been taking
it beforehand, there may be the benefit as
soon as you realize that you’re pregnant
and stepping up your folic acid. But absolutely,
the best thing is to take it before you actually
become pregnant. Now, of course, we can also
have twinning. About one pregnancy in 90 will