An Rh -ve female, conceive twin boys in her first pregnancy. What is the probability of suffering from erythroblastosis foetalis in this first pregnancy by the Rh +ve foetus?

Solution:

Erythroblastosis fetalis occurs when an Rh-negative mother carries an Rh-positive fetus in subsequent pregnancies. During the first pregnancy, the mother's body may get sensitized to the Rh antigen if fetal blood enters her circulation. However, erythroblastosis fetalis typically does not occur in the first pregnancy itself because the mother's immune system has not yet produced enough antibodies to significantly affect the fetus. Therefore, the probability of erythroblastosis fetalis in the first pregnancy is 0%.