You probably know your blood group as being for example O positive (O +) or O negative (O -). The positive or negative is the presence of the Rhesus factor.
Incidence of Rh-negative factor in Sri Lankan context is about 4-5%
Overall, an Rh- woman having the chance of an Rh+ fetus is about 60% irrespective of the father’s blood group.
What should you know when your blood group is Rhesus negative?
If you are an Rh- mother and if you are carrying a Rh+ fetus at some point of your pregnancy or labour Rh+ red blood cells from the fetus can cross over to the mothers side and form antibodies against Rhesus factor, then this mother is called Rh sensitised mother.
Times you can get ‘sensitised’ if you are Rh- and carrying Rh+ fetus
- Miscarriages
- Ectopic Pregnancy
- Any proceed you are Rh- such as amniocentesis (passing a needle into the womb)
- Anti-partum haemorrhage
- Intra partum or at the time of separation of the placenta in normal labour and caesarean section
Preventing Rh Sensitisation
Thanks to modern scientific invention a vaccination method available to prevent sensitisation.
So if you are Rh- mother you must tell your doctor to give you antiD Gama-globulin at the time of any of those events.
So, if you are Rh- the doctor will test your Rh anti bodies beyond 22 weeks of pregnancy. In some countries you will be given 2 doses of antiD at 28 weeks and 34 weeks to neutralise silent feto-maternal transfusion (the blood flow from fetus to mother). This is called antenatal prophylaxis.
Similarly at the time of childbirth the umbilical cord blood is tested for blood group and Rh and direct Coombs test. And if the baby is negative there is no need to give antiD prophylaxis. If the baby is positive within 72 hours of childbirth you will be given one vial of antiD.
If this preventive measures fail you will get sensitised. That means Rh+ red cells form antibodies in the maternal blood and this antibody crosses across the placenta to the fetus. Then the fetus develops destruction of red cells within its blood. As a result, fetus anaemic and swollen and can develop, a condition called hydrofetalis or will die inside the uterus. If the baby is born, baby’s liver cannot handle red cell destruction and the baby becomes yellow or jaundiced. This yellowish bile pigments can damage fetal brain nucleus and leads to condition called Kernicterus, and baby will be having a condition similar to severe mental retardation and cerebral palsy. If this sort of mother is found during antenatal period, special fetal medicine team will have to do specialized treatment methods.