Anal dilation during labor

ObjectiveTo determine the incidence and range of anal dilation during the final phase of the second stage of labor and shortly after delivery; determine whether parity affects anal dilation; and obtain anthropometric data for future projects.MethodsThe anal diameter was measured on admission, when the fetal head crowned, and after suturing perineal injury in 142 women delivered between August 2008 and May 2009 at University Hospital Pilsen and District Hospital Klatovy, in the Czech Republic.ResultsThe anus was dilated during the second stage of labor in all women, and differences between primiparas and multiparas were not significant. The medians for both the anteroposterior and transverse diameters were 25 mm. No measured variable was statistically associated with anal sphincter dilation.ConclusionAnal dilation during the second stage of labor causes anthropometric changes to the perineum. This ought to be considered when designing anthropometric studies and in studies aiming at minimizing anal sphincter trauma during delivery.