Concept:Rhesus factor incompatibility can cause serious pregnancy complications, so it is checked during marriage counseling.
Explanation:The Rhesus (Rh) factor is a protein present on the surface of red blood cells.
A person is Rh-positive if the protein is present, and Rh-negative if it is absent.
A risk arises when an Rh-negative mother conceives a child with an Rh-positive father.
The baby may inherit the Rh-positive factor from the father.
The mother’s immune system can then produce antibodies against the baby’s Rh-positive blood cells.
These antibodies usually do not harm the first pregnancy, but they can affect later pregnancies severely.
This condition is known as Rh incompatibility, which may lead to hemolytic disease in the newborn.
Therefore, couples are advised to know their Rhesus factor status before marriage.
Height, fingerprints, and skin colour are not medical concerns, so they are not considered in marriage counseling.
Answer:C. Rhesus factor