- Objective: To characterize seasonal patterns of placental abruption among Jewish and Bedouin parturients in the Southern part of Israel. Methods: A retrospective population-based study comparing all singleton pregnancies of patients with and without placental abruption was conducted. Deliveries occurred between the years 1988 and 2010. A 'classical' model of time series was used, allowing to assess trend and periodic patterns of placental abruption. Results: During the study period, 241,408 deliveries took place, of which 1685 (0.7%) were complicated with placental abruption. Placental abruption was significantly more common among Bedouin parturients: 0.77% (n = 948) vs. 0.623% (n = 737), p < 0.001. A non-linear negative correlation was noted in the incidence of placental abruption (coefficient = -0.002) during the entire study period. Time series analysis demonstrated annual cycle frequency, seasonal cycle and weekly cycle of placental abruption. The seasonal incidence of placental abruption was higher during spring (B = 7.15) and lower during summer (reference) for both populations (Jewish and Bedouins). Weekly cycle showed significantly higher incidence on Saturday (B = 3.4) and lowest on Tuesday (B = -4.66) for both groups. The daily differences were accentuated in the Bedouin population (B = 3.7 vs. B = 2.93 in the Jewish population). Conclusion: Placental abruption was significantly more common in the Bedouin population. Both populations demonstrated the same annual and seasonal patterns, with higher incidence in spring and autumn.