these had been tested again and again. The most important stress for the fetus is hypoxia.  In a normal pregnancy and labour hypoxia is prevented by the physiological mechanisms in place. Please read the structure and function of placenta. Placenta acts as the fetal lung during pregnancy and labour.

Consider position of the presenting part during delivery, has the fetus undergone the appropriate cardinal movements through the pelvis, any obstruction could cause stress. Fetal axis pressure is exaggerated when liquor is low. 

Could also consider pushing methods, valsalva pushing and hyperventilation have links to fetal hypoxia. 

You need to define what you mean by "fetus in the pelvis".  Are you looking for a relationship to fetal station?  Hyperstimulation can decrease the time available for recovery.  The lower the station the more restrictive the blood flow in those cases with tight nuchal cords. I would suggest you design your study with input from an actively practicing obstetrician so that you understand their thinking on when they intervene for presumed or risk for hypoxia.

its relation between contraction and umblical cord position and placenta position.

ofcourse they are so many factors depond on

Though the origin of fetal distress is hypoxia, there are various related factors. Currently it is preferable to call None reassuring fetal heart pattern. The causes may include compression of umbilical cord between the maternal pelvic bones, abrasio placenta, inadequate perfusion of nutrients and oxygen through placenta, titanic uterine contractions and possible other causes.