As I hinted, the cause of developmental abnormalities
that receives the most attention is not the
genetic and chromosomal ones which actually
cause most of the abnormalities where we know
of a cause. It’s about factors in the environment.
Again, there’s an emotional component to that.
People are very concerned that they
might have done something or been exposed
to something which caused an abnormality in their
child. But one important thing to understand
about this, something that’s not generally
well understood is that there’s generally
not a specific relationship between a cause and
an effect, where one cause has a particularly
clear outcome on the development of the baby.
Perhaps, the most famous agent which caused
abnormalities or teratogen, as they are known,
is thalidomide, which is a drug given to a
pregnant woman, and there’s a very high
likelihood of causing abnormalities.
People often think of the thalidomide defects as
being related to limbs and it’s certainly
true that they affect limbs. But if you remember
our diagram about frequencies, limbs are one
of the things that frequently go wrong. Therefore,
if you increase the total number of abnormalities,
then you may well increase the number of limb
abnormalities in a marked manner.
In reality, we know that thalidomide caused a whole
range of defects, and the time at which the mother
was exposed to thalidomide is a significant
factor. There are occasional agents which
have very specific effects. So some antibiotics
will specifically affect tooth development,
for instance. But I would say that they are
probably unusual rather than common.
Again, bear in mind that this is only a small proportion
of all causes of developmental abnormalities.
What are the kinds of environmental factors
that might be involved? I’ve classified
them into three groups; biological, physical,
and chemical. Biological, one example might
be infection with German measles or rubella.
This is something which can cause really significant
abnormalities in the early stages, particularly,
during the embryonic period. So, embryonic
death or heart defects, eye and ear defects
are all things that can commonly arise from
the mother being exposed to rubella. And it’s
also why it’s so important to maintain population
levels of vaccination at very high levels to
make sure the pregnant women are not exposed
to rubella in the community. Physical forces,
and although is the most common is x-rays.
Therefore, a good practice is never to radiate,
never to x-ray the abdomen of a woman of childbearing
age unless you are absolutely confident that
she’s not pregnant. So, a precautionary
principle would say, “Do not x-ray the abdomen
of a female of childbearing age,” and that
could be a very wide time span since women
could be pregnant from the age of 12 to the
age of 60 these days. Therefore, caution is
required under these circumstances.
Then finally, there are chemical causes, and I’d named
thalidomide as being perhaps the classic example
of that. But of course, these still represents
a relatively small proportion of the total
number of developmental abnormalities. But
one of the problems that can arise is that
parents often feel extremely bad about the
fact that their child has been born with an
abnormality and even though it’s inappropriate,
they may well feel personally guilty, personally
at fault. If, for instance, there was a genetic
cause, there is absolutely no fault or blame
that should attach to the parents, but nonetheless,
people will often feel that, and sometimes
the attempt to discharge that through finding
something else to blame. So that’s not an
uncommon feature of parents of children with
developmental abnormalities. They’re looking
for something outside themselves to blame,
even though in reality, they themselves were
never to blame at all. Sometimes that takes
the form of seeking compensation, but in my
experience, that’s not the main driver.
The main driver is this emotional need to
try and discharge the inappropriate guilt
they feel by finding somebody else whose fault
it might appear to be.