During that pregnancy, the mother's antibodies cross the placenta to fight the Rh positive cells in the baby's body. As the antibodies destroy the red blood cells, the baby can become sick. This is called erythroblastosis fetalis during pregnancy.
Sometimes, however, as in a lyric poem, the effect intended may be the rendering or creation of a mood, such as that of happy content, and in that case the poem may not have an easily expressible concrete theme. Lyric poems are expressions of spontaneous emotion and are necessarily short.
A narrative tells a story or a tale; drama is presented on a stage, where actors embody characters; lyric has been loosely defined as any short poem other than narrative and drama, where poets express their state of mind.