Known as the Rh factor, its full name is Rhesus factor. It is a protein found on the outer membrane of red blood cells.
Not everyone has it: those who have it are called Rh + (positive), while people whose red blood cells do not carry this protein are called Rh – (negative). The Rh + type is the most widespread and the presence or absence of this factor has no influence on the person’s state of health.
Why is it important during pregnancy?
If a woman is Rh – and has an Rh + partner, a phenomenon of incompatibility of the Rh factor between mother and child can occur, as the latter could inherit the presence of this protein from the father.
Contact between maternal blood Rh – and fetal blood Rh + could trigger a rejection reaction by the mother’s body. The maternal immune system, in fact, would recognize the baby’s blood, of type Rh +, as foreign. And it would begin to produce antibodies against the red blood cells of the unborn child (anti-D antibodies): in this case we speak of maternal immunization against Rh + blood.
Contact between different blood types: when does it occur?
Contact between maternal and fetal blood can occur:
- during childbirth
- during invasive examinations such as amniocentesis and chorionic villus sampling, methods that normally do not pose particular problems, but which could in some cases bring maternal blood into contact with fetal blood
- during a transfusion.
If the contact occurs during childbirth, the anti-D antibodies produced by the mother would not have the time necessary to harm the unborn child.
The situation is different in subsequent pregnancies or if the contact occurred during pregnancy. In these cases, in fact, the anti-D antibodies produced by the mother would have plenty of time to cross the placenta and attack the fetal red blood cells. When this happens, a condition of anemia occurs that can reach very serious levels, leading in some cases to the death of the baby in the womb.
What can be done? Maternal and fetal surveillance
Fortunately, the cases of babies who die in utero due to this disease are less than 10%. And this is thanks to the improvement of maternal-fetal surveillance.
Before trying to get pregnant, each couple should know their blood type and Rh factor, to identify possible cases of incompatibility. If this occurs, it is necessary for the expectant mother to undergo the indirect Coombs test: this analysis is able to establish whether the mother is producing anti-D antibodies against the baby’s red blood cells.
If so, the fetus and mother will be monitored closely. In some cases, it may be necessary to transfuse the baby through the umbilical cord, or immediately after delivery to prevent the development of anemia.
Joycelyn Elders is the author and creator of EmpowerEssence, a health and wellness blog. Elders is a respected public health advocate and pediatrician dedicated to promoting general health and well-being.
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