FAMILY MEDICAL CARE: Rh BABIES
In Western lands such as Australia, New
per cent of people contain a blood factor, or
"antigen" called the Rh factor. This is short
for "rhesus," because it was first discovered in
rhesus monkeys. These people are referred to as
Rh positive. The remaining
per cent do not have the Rh factor, and are
called Rh negative.
The Rh factor is a complex, inherited
Problems are possible when an Rh negative woman becomes
pregnant to her Rh positive husband and the
foetus is Rh positive.
At the time of labour, some of the baby's
Rh positive blood enters the maternal
circulation. This can cause the production of
chemicals called "antibodies," which will
circulate in the mother's blood from that time
on. The risks of this having an adverse effect
on the first baby are not high, but if a
subsequent pregnancy yields another Rh positive
baby, then risks start to mount. The mother's
antibodies can pass the placental barriers and
enter the foetal circulation. Here they can have
a highly destructive effect. They can
progressively destroy the baby's red cells. In
severe instances they can result in the death of
the infant before birth.
An enormous amount of work has been carried
out to try to prevent this situation from
occurring. It is now well established that if an
Rh negative woman receives a blood transfusion
during her life, this may act in a similar
manner, and anti-Rh antibodies may be formed.
This may have a similar adverse effect on her
next baby, whether it is the first or not.
In general terms,
the risks to the first baby are small, if the
mother has not previously been sensitized with a
Rh positive blood transfusion or injection. But
with each subsequent pregnancy, the risk to the
foetus increases dramatically. Many methods of
gauging the risk to the infant have been worked
out. As pregnancy advances, samples of the fluid
in which the baby swims (called the amniotic
fluid) can be checked, and the rate of red cell
destruction can be calculated from the amount of
a product called bilirubin contained in the
fluid. The greater the amount, the higher the
risk to the foetus.
Babies adversely affected were often given
an "exchange transfusion" soon after birth. In
this way, their affected blood was completely
removed and fresh blood introduced into their
system. This method saved many lives.
A New Zealand obstetrician named Liley
devised an ingenious system for giving affected
babies a transfusion while they were still in
the womb. Many lives were also saved in this
However, the most recent advance in the
field has been a dramatic one. Mothers who are
Rh negative and are carrying an Rh positive baby
can now be given a special injection of high
potency "anti-D gamma globulin" within
seventy-two hours of the birth of the baby. This
effectively reduces the formation of maternal
antibodies to the baby's cells. In short, it
removes the possibility of Rh disease occurring
in a subsequent pregnancy.
This must be carried out on each occasion.
The method has now been in operation for several
years, and the results are extremely promising.
It may not completely eliminate Rh disease, but
could go a long way in this direction.
There are still many women around who are
reproducing, and who had their initial pregnancy
prior to the introduction of the special serum.
They run the original risks, and the serum will
be of no value to them, for they have already
developed the antibodies.
But for women having their first babies,
the method offers unequalled protection. It is
one of the major advances of this modern era. In
due course it may completely remove the need for
exchange transfusions, or for Liley's uterine
transfusions. It will make the world a happier
place. It will make many mothers much happier