References
  1. Selmer-Olsen T, Nohr EA, Tappert C, Eggebo TM. Incidence and risk factors for obstetric anal sphincter ruptures, OASIS, following the introduction of preventive interventions. A retrospective cohort study from a Norwegian hospital 2012-2017. Sex Reprod Healthc. 2019;22:100460.
  2. Farrar D, Tuffnell DJ, Ramage C. Interventions for women in subsequent pregnancies following obstetric anal sphincter injury to reduce the risk of recurrent injury and associated harms. Cochrane Database Syst Rev. 2014 (11):CD010374. doi(11):CD010374.
  3. Gurol-Urganci I, Cromwell DA, Edozien LC, Mahmood TA, Adams EJ, Richmond DH, et al. Third- and fourth-degree perineal tears among primiparous women in England between 2000 and 2012: time trends and risk factors. BJOG. 2013;120(12):1516–25.
  4. van Bavel J, Hukkelhoven CWPM, de Vries C, Papatsonis DNM, de Vogel J, Roovers JWR, et al. The effectiveness of mediolateral episiotomy in preventing obstetric anal sphincter injuries during operative vaginal delivery: a ten-year analysis of a national registry. Int Urogynecol J. 2018;29(3):407–13.
  5. Jangö H, Langhoff-Roos J, Rosthøj S, Sakse A. Modifiable risk factors of obstetric anal sphincter injury in primiparous women: a population-based cohort study. Am J Obstet Gynecol. 2014;210(1):59.e1-59.e596.
  6. de Leeuw JW, de Wit C, Kuijken JP, Bruinse HW. Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery. BJOG. 2008;115(1):104–8.
  7. Meister MR, Cahill AG, Conner SN, Woolfolk CL, Lowder JL. Predicting obstetric anal sphincter injuries in a modern obstetric population. Am J Obstet Gynecol. 2016;215(3):310.e1–7.
  8. Simpson KR, Knox GE. Fundal pressure during the second stage of labour. MCN Am J Matern Child Nurs. 2001;26(2):64-71. doi:10.1097/00005721-200103000-00004
  9. Merhi ZO, Awonuga AO. The role of uterine fundal pressure in the management of the second stage of labour: a reappraisal. Obstet Gynecol Surv. 2005;60(9):599-603. doi:10.1097/01.ogx.0000175804.68946.ac
  10. Hofmeyr GJ, Vogel JP, Cuthbert A, Singata M. Fundal pressure during the second stage of labour. Cochrane Database Syst Rev. 2017;3(3):CD006067. Published 2017 Mar 7. doi:10.1002/14651858.CD006067.pub3
  11. Dietz HP. Exoanal Imaging of the Anal Sphincters. J Ultrasound Med. 2018;37(1):263-280. doi:10.1002/jum.14246
  12. Turel Fatakia F, Subramaniam N, Bienkiewicz J, Friedman T, Dietz HP. How repeatable is assessment of external anal sphincter trauma by exoanal 4D ultrasound?. Ultrasound Obstet Gynecol. 2019;53(6):836-840. doi:10.1002/uog.20175
  13. Valsky DV, Messing B, Petkova R, Savchev S, Rosenak D, Hochner-Celnikier D, Yagel S. Postpartum evaluation of the anal sphincter by transperineal three-dimensional ultrasound in primiparous women after vaginal delivery and following surgical repair of third-degree tears by the overlapping technique. Ultrasound Obstet Gynecol 2007; 29: 195–204
  14. Bruce A.Orkin,M.D. SvetlanaB.Sinykin,B.A. PatriciaC.Lloyd,Sc.M The Digital Rectal Examination Scoring System (DRESS) Dis Colon Rectum 2010; 53: 1656 –1660
  15. Cosner KR. Use of fundal pressure during second- stage labour. A pilot Study. J Nurse Midwif. 1996;41: 334–337.
  16. Cuerva MJ, Tobias P, Espinosa JA, et al. Intrapartum ultrasound prior to Kristeller maneuver: an observa- tional study. J Perinat Med. 2015;43:171–175.
  17. Malvasi A, Montanari Vergallo G, Tinelli A, et al. Can the intrapartum ultrasonography reduce the legal liability in distocic labour and delivery? J Matern Fetal Neonatal Med. 2018;31:1108–1109
  18. Moiety FM, Azzam AZ. Fundal pressure during the second stage of labour in a tertiary obstetric center: a prospective analysis. J Obstet Gynaecol Res 2014; 40: 946–953
  19. Matsuo K, Shiki Y, Yamasaki M, Shimoya K. Use of uterine fundal pressure maneuver at vaginal delivery and risk of severe perineal laceration. Arch Gynecol Obstet 2009; 280: 781–786.
  20. Verghese TS, Champaneria R, Kapoor DS, Latthe PM. Obstetric anal sphincter injuries after episiotomy: Systematic review and meta‐analysis. Int Urogynecol J. 2016;27:1459–1467.
  21. Drusany Staric K, Lukanovic A, Petrocnik P, Zacesta V, Cescon C, Lucovnik M. Impact of mediolateral episiotomy on incidence of obstetrical anal sphincter injury diagnosed by endoanal ultrasound. Midwifery. 2017;51:40-43. doi:10.1016/j.midw.2017.05.008
  22. Jiang H, Qian X, Carroli G, Garner P. Selective versus routine use of episiotomy for vaginal birth. Cochrane Database Syst Rev. 2017;(2):CD000081.
  23. Coats PM, Chan KK, Wilkins M, et al. A comparison between midline and mediolateral episiotomies. Br J Obstet Gynaecol. 1980;87:408-412.
  24. Aukee P, Sandstrom H, Kairaluoma MV. The role of mediolateral episioto- my during labour: analysis of risk factors for obstetric anal sphincter tears. Acta Obstet Gynecol Scand. 2006;85(7):856-860.
  25. Poen AC, Felt-Bersma RJ, Dekker GA, et al. Third degree obstetric perineal tears: risk factors and the preventative role of mediolateral episiotomy. Br J Obstet Gynaecol. 1997;104:563-566.
  26. Eogan M, Daly L, O’Connell PR, et al. Does the angle of episiotomy affect the incidence of anal sphincter injury? BJOG. 2006;113:190-194.
  27. Youssef A, Salsi G, Cataneo I, et al. Fundal pressure in second stage of labour (Kristeller maneuver) is associated with increased risk of levator ani muscle avulsion. Ultrasound Obstet Gynecol. 2019;53(1):95-100. doi:10.1002/uog.19085
  28. Takmaz T, Aydın S, Gorchiyeva İ, Karasu AFG. The usual suspect: cross-sectional study of fundal pressure at second stage of delivery and the association with pelvic floor damage. Int Urogynecol J. 2020;10.1007/s00192-020-04523-x. doi:10.1007/s00192-020-04523-x
Figure 1: Imaging of the anal sphincters with 3D transperineal ultrasound. The white stars indicates a discontinuity in the internal anal sphincter in 3 slices that corresponds to a complete IAS defect.Figure 2: Imaging of the anal sphincters with 3D transperineal ultrasound. The black arrows indicates a discontinuity in the internal anal sphincter in 2 slices that corresponds to a incomplete IAS defect.Figure 3: Thinning of internal anal sphincter indicated with white arrows.