Introduction & Objective: The third stage of labor, which begins immediately after delivery of the fetus, involves the separation and expulsion of the placenta. The purpose of study was to determine some Factors on duration of third stage of labor.

Materials & Methods: This was a descriptive and analytical study that was carried out in university-affiliated teaching hospital, Hamadan city, Iran.  A total of 456 parturient women were recruited and immediately after delivery of fetus, duration of third stage of labor (separation and expulsion) was recorded. Data processing and statistical analysis were performed using EPI/ PC.

Results: The results revealed that duration of third stage of labor in majority of selected women (49.6%) was 5-7 minutes. A considerable percentage of selected women had 21-30 years old. Higher percentage of women (41.9%) had primary education. Nearly 58.3% of selected women did not use analgesic and episiotomy performed in majority of selected women (67.5%). Majority of women (84.6%) of selected women had normal anthropometrics profile. Regression analysis showed no significant relation between third stage of labor with mother's parity (P> 0.05). But there are significant relation between episiotomy, usage analgesic and newborn weight with third stage of labor (P= 0.00).

Conclusion: Regression analysis presented that usage analgesic, birth weight and episiotomy had first, second and third ranks on duration of third stage of labor. Maternal age, gestational age and life style were followed. These parameters can be applied in prediction of duration of third stage of labor.