Explain $Rh$-incompatibility in humans.

(N/A) $1$. $Rh$-incompatibility occurs when an $Rh$-negative mother carries an $Rh$-positive fetus.
$2$. During the first pregnancy,the mother's blood is exposed to the $Rh$ antigens of the fetus during delivery,leading to the formation of anti-$Rh$ antibodies in the mother's blood.
$3$. In subsequent pregnancies,these anti-$Rh$ antibodies can cross the placenta and destroy the $Rh$-positive fetal red blood cells,causing severe anemia and jaundice,a condition known as erythroblastosis fetalis.
$4$. This can be prevented by administering anti-$Rh$ antibodies (RhoGAM) to the mother immediately after the first delivery.