Assistant Professor of Obstetrics & Gynecology, Ahwaz University of Medical Sciences, Ahwaz, Iran.
Background & Aims: Accurate knowledge about gestational age is very important in taking decision for pregnancy management and termination. According to Naegele’s rule the length of pregnancy is 280 days after LMP and according to studies performed in Harvard University, duration of pregnancy in nullipare and multipare women has been respectively 288 and 283 days and according to a study performed in Oxford University it is influenced by factors such as age, parity, some illnesses and personal habits. Materials and methods: In this retrospective study, all laboring women admitted in Ahwaz Medical University Hospitals in 2007 including 689 nulliparas and 774 multiparas with true labor pain and reliable LMP were studied for pregnancy duration. Data were analyzed by SPSS software. Results: Mean duration of pregnancy was 273.17, 274.31and 273.77 days in nulliparas, multiparas and overall respectively. Parity has no significant association with pregnancy duration. According to the sonography below 26 weeks duration of pregnancy is calculated 270.07 days which had no significant relationship with LMP. Conclusion: According to this study parity has no effect on pregnancy duration. Mean pregnancy duration was shorter comapared to Naegele’s rule and Harvard University studies.