Background: There is dearth of reports from Iran regarding the prevalence of postterm pregnancy and its complications. The present study was conducted to evaluate the prevalence, management and outcome of prolonged pregnancies.

Methods: This cross-sectional study included data from the hospital records of all women referred to Shariati Hospital, Tehran, from 2001 to 2002 with pregnancies of more than 40 weeks in duration. Pregnancies ≥40-42 weeks were considered postdate and those more than 42 weeks postterm pregnancy. The data compiled from the hospital records were subjected to t, χ² and Mann-Whitney U tests.

Results: Of the 1500 deliveries in this hospital, 98 patients were included in this study, 66.3% of whom were nullipara and 33.7% multipara. The prevalence of postterm pregnancy was estimated to be 3.3%. Cervix dilation of 2 cm or less on admission occurred in 65 women (73.3%). The mean Bishop score was 4.31. Of the 62 fetuses that underwent assessment tests, 54 (87.1%) were normal. The median time between the last test and induction of labor was 2.1 days, and 2.6 days for cesarean deliveries, which was not a significant difference (P=0.6). Cervical ripening with misoprostrol was performed in 36 cases (36.7%) and was successful in 18 cases. In this group, the median time for cervical ripening in multiparas was significantly less than nulliparas (4 vs. 7 hrs, P=0.004). Women not subjected to cervical ripening had a higher cesarean rate than those who did undergo cervical ripening (74.7% vs. 66.1%), although this difference was not significant (P=0.9). Vaginal and cesarean delivery rates showed no significant difference between cases that underwent induction with oxytocin and those subjected to cervical ripening with misoprostol (P=0.9). The mean Apgar score was 9.5, with all scores above 6. There were no cases of neonatal hypoglycemia, hypocalcemia, NICU admission or prenatal death. The mean nursery stay was 1.84 days with a range of 1-8 days.

Conclusions: The prevalence of postterm pregnancies was 3.3% in this study, due in part to erroneous estimation of gestational age. Sonography exam in the first half of pregnancy can provide a better estimation of gestational age and thereby reduce the rate of postterm pregnancy. Cervical ripening and induction of labor shorten the duration of pregnancy; however, whether it has any beneficial effect on neonatal outcome remains controversial.