ObjectivesShoulder dystocia (SD) is an obstetrical emergency with well-recognized risk factors. We aimed to identify trends of changes in the specific contribution of risk factors for SD over time.MethodsA nested case control study comparing all singleton deliveries with and without SD was undertaken. A multivariable logistic regression model was used in order to identify independent risk factors for SD and a comparison of the prevalence and the specific contribution (odds ratio (OR)) of the chosen risk factors in three consecutive eight-year intervals from 1988 to 2014 was performed.ResultsDuring the study period, there were 295,946 deliveries. Of them 514 (0.174%) were complicated with SD. Between 1988 and 2014 the incidence of SD has decreased from 0.3% in 1988 to 0.1% in 2014. Using a logistic regression model grandmultiparity, diabetes mellitus (DM), fetal weight, and large for gestational age (LGA) were found to be independent risk factors for SD (OR 1.25 95% CI 1.04–1.51, p=0.02; OR 1.53 95% CI 1.19–1.97, p=0.001; OR 1.002 95% CI 1.001–1.002, p ConclusionsThe individual contribution of selected risk factors for the occurrence of SD has significantly changed throughout the years. The contribution of DM has demonstrated a linear increase over time, emphasizing the great impact of DM on SD.