Amir Hussein Asgari safdar - M.Sc. students of animal physiology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.
Hussein Daghigh Kia - Assistant Prof, Department of Animal Science, Faculty of Agriculture, University of Tabriz,Tabriz, Iran.
Ramin Farhadi - M.Sc. students of animal physiology, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.

Labor is a physiological event involving a sequential, integrated set of changes within the myometrium, deciduas, and uterine cervix that occur gradually over a period of days to weeks. Biochemical connective tissue changes in the uterine cervix appear to precede uterine contractions and cervical dilation, and all of these events usually occur before rupture of the fetal membranes. In other word Parturition is the process of delivery of the fully grown fetus on the completion of the normal pregnancy period

parturition, labor, hormones