We assist women in all stages of life

What do we have to thank the rhesus monkeys for?

In every pregnancy, the blood group including the rhesus factor D is determined as part of the maternity guidelines.
The Rh factor (Rh) is a group of surface proteins of the red blood cells. There are five surface antigens in total: D, C, c, E and e and Rh factor D is the most important Rh parameter.

The Rh system was first demonstrated in 1940 by Karl Landsteiner and Alexander Solomon Wiener in rhesus monkeys and is, next to the AB0 system, the second most important blood group characteristic in humans.

If this factor D is present, the blood group is considered Rh-positive and if it is not present, Rh-negative.

About 85% of people in Europe are Rh positive (RhD+) and 15% are Rh negative (RhD-). These percentages vary by ethnicity; people of African descent show about 8% Rh negativity and people of Chinese descent show about 0.3%.

A woman with Rh negative blood can carry a foetus with Rh positive blood if the father has Rh positive blood. This is called Rh incompatibility.

This situation can be problematic if the Rh-positive blood of the foetus enters the bloodstream of the Rh-negative mother. The mother’s immune system identifies the foetus’s red blood cells as foreign bodies and produces Rh antibodies against them, which destroy the baby’s Rh-positive blood cells.
This antibody production is called Rh sensitisation.
If the red blood cells of the foetus or newborn are thereby broken down faster than the foetus can produce new ones, anaemia can develop in the foetus. Such degradation is called haemolytic disease in the foetus (erythroblastosis fetalis) or in the newborn (erythroblastosis neonatorum).
The pregnancy in which sensitisation occurred is not affected. However, once women are sensitised, complications are more likely to occur with each future pregnancy if the foetus’ blood is Rh-positive.

• Important to know: Rh incompatibility usually does not cause problems in the first pregnancy. However, the risk is greater with each subsequent pregnancy because Rh antibodies are produced in greater quantities and at an earlier stage. The mothers do not have any symptoms of this.

What can be done about it

Since sensitisation cannot be reversed, prevention of this situation is the gold standard.
This means preventing Rhesus AK from passing from the fetus into the maternal blood. This can be achieved by intravenous administration of anti-D immunoglobulin (rhesus prophylaxis).
These anti-D immunoglobulins are made from human blood donations and can be considered very safe.

When to administer rhesus prophylaxis

Anti-D administration is recommended in all Rh negative pregnant women and Rh positive fetuses at higher risk of fetomaternal transfusion, ideally within 72h.
Nowadays, fetal Rh determination from maternal blood is possible even before birth, or from the 18th week of gestation.
Rhesus prophylaxis (anti-D immunoglobulin) can then be administered specifically only to Rh pregnant women and Rh+ fetuses.
In risk situations for fetomaternal transfusion and unknown fetal BG, anti-D administration within 72 hours is recommended.

The following are considered risk situations for fetomaternal transfusion:

Birth, Termination of pregnancy (medical or surgical), Abortion (medical or surgical), Bladder mole , Chorionic villus sampling , Amniocentesis, Cordocentesis , Extrauterine gravidity, Vaginal bleeding (Abortus imminens, Premature placental abruption, Placenta previa) , External turn , Abdominal trauma.

Anti-D administration to be repeated every 12 weeks until birth.

Fetal blood grouping before birth

In Europe, about 40 per cent of RhD-negative women give birth to RhD-negative offspring, which means that in 40 per cent of cases anti-D administration during pregnancy is not necessary.
The Swiss Society for Gynaecology and Obstetrics recommends molecular genetic fetal RHD testing from maternal blood in all RhD-negative pregnant women between the 18th – 24th week of pregnancy.

• If the unborn child tests RhD-positive, the usual RhD prophylaxis with 300ug Rhophylac is given in the 28th week of pregnancy or earlier in risk situations.
• If the unborn child tests RhD-negative, there is no need for RhD prophylaxis during pregnancy.

In any case, the RhD factor is determined after birth according to the guidelines,
preferably from umbilical cord blood.

The costs for the fetal blood group determination are covered by the health insurance funds.

Rhesus D-negative pregnant women must nowadays be informed about the possibility of non-invasive molecular genetic fetal RHD determination and thus about the potential waiver of anti-D administration.

„Determination of rhesus factor in the child during pregnancy“, Gesundheit heute, SRF
Interview with Dr. Alina Staikov