Obstet Gynecol 116 (6): 1281 - 1287, 2010. doi: 10.1097/AOG.0b013e3181fdef6e Etiology Protracted labor may result from fetopelvic disproportion (the fetus cannot fit through the maternal pelvis), which can occur because the maternal pelvis is abnormally small or because the fetus is abnormally large or abnormally positioned (fetal dystocia).