Final answer:
RhoGAM is administered to an Rh-negative pregnant woman at 28 weeks of gestation and within 72 hours after birth to prevent hemolytic disease of the newborn (HDN).
Step-by-step explanation:
The appropriate time during pregnancy to administer Rho(D) immune globulin, commonly known as RhoGAM, to an Rh-negative woman is during the 28th week of gestation. RhoGAM is crucial in preventing the development of Rh antibodies which can lead to hemolytic disease of the newborn (HDN), a serious condition that involves the destruction of the fetus's red blood cells. This medication is administered again within 72 hours following birth to ensure any fetal Rh-positive erythrocytes that may have entered the maternal circulation are destroyed, which significantly decreases the incidence of HDN in subsequent pregnancies.