ORIGINAL ARTICLE It is the first birth that does the damage: a cross-sectional study 20 years after delivery Ixora Kamisan Atan 1,2 & Sylvia Lin 3,4 & Hans Peter Dietz 1 & Peter Herbison 5 & Peter Donald Wilson 5 & for the ProLong Study Group Received: 30 August 2017 /Accepted: 26 February 2018 # The International Urogynecological Association 2018 Abstract 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. Methods 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 standard- ized 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). Results 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. Conclusions 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. Keywords Anal sphincter tears . Levator ani avulsion . Pelvic floor trauma . Pelvic organ prolapse . Vaginal parity Introduction In this era of increased women’ s life expectancy, maternal birth trauma such as levator ani muscle (LAM) avulsion and obstetric anal sphincter injury (OASIS) is seen as increasingly relevant. This may be attributed to the association with long- term morbidity including pelvic organ prolapse (POP), pelvic floor and sexual dysfunction, fecal and/ or anal incontinence (AI), affecting women’ s quality of life (QoL) and utilization of healthcare resources [1–5]. Pelvic organ prolapse affects 3– 50% [6, 7] of the female population, involving a 10–20% lifetime risk of having prolapse surgery at a cost of over one billion USD annually (in the USA) [4, 5]. The long-term cost associated with AI secondary to OASIS was reported to be USD17,166 per patient in 1996 [8]. Levator trauma following vaginal delivery may be in the form of an avulsion (macrotrauma) and/ or irreversible This study was presented as an oral presentation during the 41st IUGA Annual Meeting, Cape Town, 2016 * Ixora Kamisan Atan dr_ixoratan@hotmail.com 1 Sydney Medical School Nepean, The University of Sydney, Sydney, Australia 2 Department of Obstetrics & Gynecology, Universiti Kebangsaan Malaysia Medical Centre (UKMMC), Jalan Yaacob Latiff, Bandar Tun Razak, Cheras, 56000 Kuala Lumpur, Malaysia 3 Women’ s Health Waikato DHB, Hamilton, New Zealand 4 Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand 5 Dunedin School of Medicine, University of Otago, Dunedin, New Zealand International Urogynecology Journal https://doi.org/10.1007/s00192-018-3616-4