From the preceding analysis of prostaglandin research in the reproductive field, it is clear that there have been three major discoveries: a) prostaglandins cause contractions of the human uterus during pregnancy; b) prostaglandins are luteolytic in many subprimate species, but not in humans; and c) prostaglandin levels in the blood and amniotic fluid are elevated during labor in many species, including humans. These important findings have led to major advances in clinical medicine and animal husbandry and to a further understanding of some of the events in the reproductive cycle.