title: Behavior of perineum during delivery before fetal head expulsion.
abstract: OBJECTIVE
  The aim of this study was to describe perineum deformation during the final part of delivery and suggest a modification of the episiotomy cut to increase accuracy for obtaining a suitable angle (45°) for surgical wound suture.
  
  
  METHODS
  This prospective study enrolled 45 primiparous women. The perineum at rest was marked with five lines (0°, 30°, 45°, 60°, 90°), and each line was marked with two dots (point A-B: to 2-3 cm from initial point in fourchette, respectively). Two digital pictures were taken: one with the women at rest and the second during fetal head crowning; displacements were calculated for each point and angle.
  
  
  RESULTS
  When the perineum is distending, the initial point of every line in the posterior fourchette moves laterally in introitus (only the 0° line remains at midline). The angle and the distance to points A and B of each line drawn do not change significantly from at rest to crowning. However, comparing original line configuration with an imaginary line from the fourchette to points A and B before expulsion, the angle and the distance is increased statistically significantly.
  
  
  CONCLUSIONS
  Perineal distension at the moment of fetal head crowning causes a linear displacement of the perineum, which causes the difference in angle between the incision and episiotomy suture. Therefore, to obtain an episiotomy suture from fourchette with an angle of 45°, theoretically, we would have several angle incision options (between 45° and 60°), with a less acute angle when the introitus cut is closer to the fourchette (45° to 6 mm and ∼60° in the fourchette) and a sharper angle with a longer episiotomy.
authors: Pelvic Floor Unit, Department of Obstetrics and Gynecology, Complejo Asistencial Universitario de León (CAULE), C/ Altos de Nava S/N, 24080, León, Spain. enriquegonzalezdiaz@hotmail.com.
authors: Enrique
authors: E
authors: Gonzalez-Díaz
authors: Department of Obstetrics and Gynecology, Complejo Asistencial Universitario de León (CAULE), León, Spain.
authors: Camino
authors: C
authors: Fernández Fernández
authors: Department of Obstetrics and Gynecology, Complejo Asistencial Universitario de León (CAULE), León, Spain.
authors: Maria Jose
authors: MJ
authors: Fernández Galguera
authors: Department of Obstetrics and Gynecology, Complejo Asistencial Universitario de León (CAULE), León, Spain.
authors: Alfonso
authors: A
authors: Fernández Corona
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000293:injuries; D036861:Delivery, Obstetric / Q000009:adverse effects*; D004841:Episiotomy / Q000379:methods*; D005260:Female; D020567:Fetal Weight; D005333:Fetus; D005865:Gestational Age; D006257:Head; D006801:Humans; D007748:Labor Stage, Second / Q000502:physiology*; D010298:Parity; D010502:Perineum / Q000502:physiology*; D011247:Pregnancy; D011446:Prospective Studies; D013536:Suture Techniques
keywords: Episiotomy technique; Mediolateral episiotomy; Obstetric anal sphincter injuries