What Is Rh?—N.Z. Draws Attention

Press, Volume CIII, Issue 30401, 28 March 1964, Page 5

What Is Rh?—N.Z. Draws Attention

[Specially Written for "The Press" by ROBYN JENKIN) “WHAT is Rhr” is a question frequently asked, and now with New Zealand making medical history in the field of pre-birth trans-, fusions, many people will want to know what it is all about.

Since the last war, when blood groups were printed on soldiers’ "meat tickets” and with the ever increasing interest in blood banks most' people know of the blood groups, A, B, AB, and O, and the additional positive or negative attached to them. It is this positive or negative symbol which denotes the presence or absence Of. the Rh factor in the person’s Mood.'

. The chemical substance making up the Rh factor is carried in the blood of about 85 per cent of all.white persons but. is absent from the remaining 15 per cent. This Rh factor is. produced through the. action of a dominant gene, and whether a person inherits one such gene, as from one parent, Or two genes, one from each parent, he will develop the Rh factor and so be Rh positive.

If, however, he inherits two recessive Rh genes he will, not develop the factor and will be Rh negative. . To the average persoh it

does not matter whether he is Rh positive or Rh negative, for on the rare occasion when he may require a blood transfusion, the blood bank will make, sure he receives blood which is compatible with his own.

But it is - almost entirely in the life of the unborn child that the Rh factor has its importance. If both parents are Rh. positive, or if both are Rh negative, or if the husband is Rh negative and the wife Rh positive, there is little chance of the offspring being harmed by the Rh factor, but in the case of the Rh negative wife and the Rh positive husband (about 12 per cent of all marriages) there is a slight possibility that the baby may be born with the anaemia and jaundice found in these cases. Because the. father in this case is Rh positive it is most likely (without going into high-powered genetics) that the baby will be Rh positive, having inherited the dominant Rh positive gene from its father. Breakdown

When this positive factor which exists in the red blood cells of the foetus passes the placenta and into the circulation of the mother (Rh negative) who does not have the Rh factor, the mother’s body makes anti-Rh antibodies which then return to the foetus and cause the breakdown of the baby’s red blood cells.

If the mother makes more antibodies, then more of the cells of the foetus will be damaged, such as the liver cells, and a severely jaundiced condition may . arise Again, if the mother makes still more antibodies, the foetus could die before birth. However, only in about bhe sixteenth of cases where the mother, is Rh. negative and the baby Rh positive do these symptoms occur. Antibodies

For instance, if an Rh negative woman is producing her first Rh positive baby, and an interchange of their blood substances does take place, the antibodies she produces are seldom strong enough to harm the foetus in any way. Again, some women in the same position just don’t produce antibodies at all. However, if a woman who has produced antibodies with her first child has a further child, She starts. off the second pregnancy with the antibodies already present in her blood from the first pregnancy, and these antibodies are ready to attack the red cells of the baby at an earlier stage. This child, too, may be born with no ill effects or. it may require an exchange transfusion. The exchange transfusion was a major breakthrough in medicine, because it saved the lives of many babies which would otherwise have died at birth or soon after. By an exchange transfusion many people imagine that all the

baby’s blood is drained off and completely replaced by a fresh supply. In actual fact, fresh blood of a group O negative which will not be affected by the mother’s Mntibodies, is injected into- the baby’s blood stream in small amounts. Soon after each Idjection an equivalent amount of blood is drawn off. Later more is injected, more drawn off, and so on until the baby’s blood has been greatly diluted by this fresh blood supply. However, the exchange transfusion is only possible after birth and there comes a

time, perhaps with the third or . fourth child, when the mother’s antibodies have developed to such 'an extent that the baby dies before full term.

In such cases the baby may be induced before fall term, say at eight months, when the antibodies have not had time to do their worst With still later pregnancies there reaches a stage when the dangerous level, yet the baby is too undeveloped to survive in the outside world; Auckland Work And it is for these cases that the newly developed prebirth transfusions can save the baby’s life. The method, devised by Dr. A W. Liley and his fellow research workers at the Post-graduate

School Obstetrics and Gynaecology, University of Auck-

land, made use of the little known fact that red blood

cells are absorbed Intact from the baby’s abdominal cavity into the baby’s circulation, One hundred c.c.’s of red cells of a group known to be compatible with that of the baby but unable to be affected by the mother’s antibodies, were injected into the baby’s abdominal cavity from which they were absorbed into the circulation. These blood cells, followed by another injection 10 days later, meant that the baby could develop normally, for a longer time before being induced prematurely, 110

Nowadays nothing is left to chance, and routine ante-natal care includes blood grouping of the mother, and grouping the husband of an Rh negative wife. Rh negative mothers

receive further blood tests during the pregnancy to see whether they are building up antibodies, and, if this is so, a careful check is kept to make sure the antibodies have not reached a dangerous level. Even though it is less than 30 years since the Rh factor was discovered a great deal has been done to reduce the infant mortality because of this blood factor—exchange transfusions, pre-birth transfusions, and now, from America, talk of a method to eliminate the build up of anti-

All these are steps towards the day when the Rh factor and its effects wiU become a historical footnote in a medical text book.