Question

Example of $Rh$ incompatibility is

• A. mother ${Rh}^{-}$ and father ${Rh}^{+}$
• B. father ${Rh}^{-}$ and mother ${Rh}^{+}$
• C. Both mother and father are ${Rh}^{-}$
• D. Both mother and father are ${Rh}^{+}$

Answer 1

The correct option is A mother ${Rh}^{-}$ and father ${Rh}^{+}$

Erythroblastosis fetalis is a condition which arises when a female is Rhesus negative (recessive) and the male is Rh positive (dominant)

The child from such a couple inherits the Rh positive trait from the father.

The Rh-positive red blood corpuscles of a foetus in the womb enter the blood of the mother where the development of Rh antibodies takes place in mother's blood.

These antibodies along with mother's blood on reaching the fetal circulation cause the clumping of fetal RBC. The first child is born normal because by that time the number of antibodies in mothers that remain lesser but they increase with successive pregnancy.

Hence, the correct answer is 'mother $R{h}^{-}$ and father $R{h}^{+}$'