It is the first birth that does the damage: a cross-sectional study 20 years after delivery

  • Ixora Kamisan Atan
  • Sylvia Lin
  • Hans Peter Dietz
  • Peter Herbison
  • Peter Donald Wilson
  • for the ProLong Study Group
Original Article


Introduction and hypothesis

Levator ani muscle (LAM) and anal sphincter tears are common after vaginal birth and are associated with female pelvic organ prolapse and anal incontinence. The impact of subsequent births on LAM and external anal sphincter (EAS) integrity is less well defined. The objective of this study was to determine the prevalence of LAM and EAS trauma in primiparous (VP1) and multiparous (VP2+) women who had delivered vaginally to assess if there were differences between the two groups. The null hypothesis was: there is no significant difference in the prevalence of LAM and EAS trauma between the two groups.


This was a cross-sectional study involving 195 women, participants of the Dunedin arm of the ProLong study (PROlapse and incontinence LONG-term research study) seen 20 years after their index birth. Assessment included a standardized questionnaire, ICS POP-Q and 4D translabial ultrasound. Post-imaging analysis of LAM and EAS integrity was undertaken blinded against other data. Statistical analysis was performed using Fisher’s exact test and results were expressed as odds ratios (OR).


LAM avulsion and EAS defects were diagnosed in 31 (16%) and 24 (12.4%) women respectively. No significant difference in the prevalence of levator avulsion and EAS defects between primiparous (VP1) and multiparous (VP2+) women who had delivered vaginally (OR 1.9, 95% CI 0.72–5.01, p = 0.26) and (OR 1.2, 95% CI 0.4–3.8, p = 0.76) respectively.


Most LAM avulsions and EAS defects seem to be caused by the first vaginal birth. Subsequent vaginal deliveries after the first were unlikely to cause further LAM trauma.


Anal sphincter tears Levator ani avulsion Pelvic floor trauma Pelvic organ prolapse Vaginal parity 



The authors would like to thank the women who participated in this study, and Gaye Ellis, the Research Coordinator in Women’s and Children’s Health, Department of Obstetrics & Gynecology, Dunedin School of Medicine & Health Sciences, University of Otago, for her involvement in the follow-up administration. We also acknowledge the loaned ultrasound equipment from GE Medical for this study.


This study was funded by The University of Otago Research Grant, without having any influence or conflicts of interest in the results of the study.

Compliance with ethical standards

Details of ethics approval

This study was approved by the New Zealand Health and Disability Ethics Committee (LRS/05/04/009/AM01).

Conflicts of interest

HP Dietz has received honoraria from GE Medical. None of the other authors has any conflict of interest to declare.


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Copyright information

© The International Urogynecological Association 2018

Authors and Affiliations

  1. 1.Sydney Medical School NepeanThe University of SydneySydneyAustralia
  2. 2.Department of Obstetrics & GynecologyUniversiti Kebangsaan Malaysia Medical Centre (UKMMC)Kuala LumpurMalaysia
  3. 3.Women’s Health Waikato DHBHamiltonNew Zealand
  4. 4.Faculty of Medical and Health SciencesUniversity of AucklandAucklandNew Zealand
  5. 5.Dunedin School of MedicineUniversity of OtagoDunedinNew Zealand

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