Abstract: Migration of human peripheral leukocytes in response to chemotactic factors during pregnancy. The methods include determining the likelihood of a pregnant subject undergoing delivery within about 7 days by obtaining peripheral leukocytes from the pregnant subject and determining a chemotactic activity of the leukocytes, wherein an increased likelihood of delivery within about 7 days is indicated when the chemotactic activity is at a level characteristic of a full term pregnancy. Chemotactic activity is assessed by measuring migration of peripheral leukocytes towards a chemoattractant which is a factor present in a sample comprising human fetal membrane obtained from a full term pregnant subject. Other biomarkers or F-actin polarization of peripheral leukocytes are also indicative of the likelihood of a pregnant subject undergoing delivery. Further methods disclosed include minimizing complications of preterm delivery by administration of an IL-1 antagonist when there is a likelihood of preterm delivery.