FAMILY MEDICAL CARE: Rh BABIES

In Western lands such as Australia, New Zealand, and America and the U.K., about 85 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 15 per cent do not have the Rh factor, and are called Rh negative.

The Rh factor is a complex, inherited characteristic. 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 manner.

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 too.

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GENERAL HEALTH