Anal Sphincter Muscle Activity Changes in Women after Delivery

Vita Začesta

Research output: Types of ThesisDoctoral Thesis


The Doctoral Thesis was developed at Rīga Stradiņš University, Latvia. Defence: at the public session of the Council of the Clinical Medicine, on 31th March 2022 at 13.00 online via Zoom platform.An episiotomy is one of the most common surgical interventions in obstetrics. Mediolateral episiotomy is usually performed on the right side. Recent advances in pelvic floor electromyography (EMG) allow to perform functional analysis of external anal sphincter with a minimally invasive anal probe. An individual asymmetry of the sphincter exists, and it is strongly associated with postpartum incontinence, primarily when the trauma occurs on the dominant side of innervation. This Thesis aims to evaluate the external anal sphincter innervation zone distribution and EMG amplitude before and after delivery and to observe the effect of episiotomy on changes of sphincter innervation. The study is a prospective cohort study. Three hundred pregnant women were recruited to the study, and two surface EMG measurement sessions (before and 6–8 weeks after delivery) with multichannel cylindrical anal probes were performed. One hundred women participated in the third measurement session at one-year follow-up. The distribution of innervation zones and global EMG signal amplitude average rectified value was assessed, and the amplitude asymmetry index was calculated. The outcomes were compared before and after delivery between different delivery types (caesarean section, mediolateral episiotomy, spontaneous lacerations and intact perineum) and according to the asymmetry index. Additionally, the anal incontinence score was evaluated before and after delivery. The results showed a significant reduction of innervation zones in the right ventral quadrant after delivery with right side episiotomy. After delivery, a significant decrease in global EMG amplitude was observed in women with amplitude asymmetry on the right side and in those who underwent mediolateral right episiotomy. The incontinence score slightly but not significantly increased 6–8 weeks after the delivery in 20 % of caesarean and 30 % of vaginal deliveries. The main conclusions of the study are that 1) episiotomy reduces external anal sphincter muscle activity, 2) multichannel surface electromyography is a promising method to analyse the anal sphincter activity. EMG signals detected during pregnancy could be used to decide the optimal side of episiotomy, thus reducing the damage to the sphincter innervation caused by the episiotomy itself
Original languageEnglish
  • Rezeberga, Dace, First/Primary/Lead supervisor
  • Plaudis, Haralds, Second/Co-supervisor
Place of PublicationRiga
Publication statusPublished - 2022


  • Doctoral Thesis
  • Sector - Clinical Medicine
  • Sub-Sector – Obstetrics and Gynaecology
  • innervation zone
  • episiotomy
  • delivery type
  • incontinence
  • multichannel sEMG
  • external anal sphincter

Field of Science*

  • 3.2 Clinical medicine

Publication Type*

  • 4. Doctoral Thesis


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