Complex sentence: In 1939 Philip Levine and Rufus E. Stetson published their findings about a family who had a stillborn baby who died of hemolytic disease of the newborn, which included the first suggestion that a mother could make blood group antibodies owing to immune sensitization to her fetuses RBCs.
Split into simpler sentences: In 1939 Philip Levine and Rufus E. Stetson published their findings about a family who had a stillborn baby who died of hemolytic disease of the newborn. They suggested for the "first time" that a mother could make blood group antibodies owing to sensitization by her fetuses RBCs.