Prevention of shoulder dystocia related birth injuries: Myths and facts

Table 5 Incidence of shoulder dystocia in the United States between 1949 and 2005

Time periods (yr)	Number of reports	Ref. numbers of reports1	Average incidence per 100 births2
1949-1974	5	[55,65-68]	0.26%
1975-1990	10	[49,55,56,69,70-74]	1.22%
1991-2005	11	[56,74-81]	1.65%

¹Two authors presented multiple reports;

²Some reports referred to number of cases per 100 vaginal births. These were adjusted under the premise that the rate of cesarean section was 20%. Note that the rate of shoulder dystocia increased almost 5-fold by the 2^nd and more than 6-fold by the 3^rd time period as compared to the 1949 to 1974 average.