Levator trauma in labor: a challenge for obstetricians, surgeons and sonologists

Recent advances in pelvic floor assessment have led to the rediscovery of a form of maternal birth trauma that was first described in 19071 but is absent from modern textbooks. Avulsion of the pubovisceral muscle from the pelvic sidewall seems to occur in 15–30% of vaginally parous women. Its prevalence is probably on the rise, as the likelihood of trauma seems to increase with higher maternal age at first delivery. Levator avulsion appears to be a significant part of the missing link between vaginal childbirth and prolapse and is likely to be the root cause of many cases of recurrence after prolapse surgery. At present, no techniques exist for the surgical repair of resulting defects. However, it is fortuitous that, hot on the heels of the rediscovery of levator avulsion and its significance, we seem to have chanced upon a means of dealing with anterior compartment prolapse in the presence of such trauma. Transobturator fixation of anterior compartment mesh, featured in this issue by Ralf Tunn of Berlin2, appears to cross the hiatus at the site of the defect and to provide support precisely where it is most needed. As shown by Dr Tunn, the meshes used for transobturator repair are identified easily by ultrasound, and imaging has already provided some surprising insights into the nature and mechanism of action of this new surgical technique. Over the last three decades, we have learned a lot about the epidemiological link between vaginal childbirth and pelvic floor dysfunction. Vaginal delivery is associated with a relative risk of 2–3 for fecal incontinence3, and we think we know how to explain this. Trauma to the pudendal nerve was investigated extensively in the 1980s and 90s4,5. Obstetric tears of the external and internal anal sphincters are familiar to every resident in obstetrics and gynecology after their first few weeks in training, and there is a lot of ongoing work to optimize detection and postpartum repair6,7. As regards stress urinary incontinence, the relative risk is about the same3, despite the fact that we do not really know which structures are responsible. The epidemiological link between childbirth and pelvic organ prolapse is stronger and particularly well established, with a relative risk of between 4 and 108. Despite all these research data, there really are no prospects yet for preventative intervention. Elective Cesarean section, the one potentially prophylactic intervention, may well be associated with so much shortand longterm morbidity and costs to the taxpayer as to defeat the purpose. This is an unfortunate state of affairs, as demographic change in virtually all societies, especially delayed childbearing and increasing obesity, may well be leading to increased pelvic floor morbidity9,10. The ageing population and altered perceptions of health needs will also impact on the workload of medical and paramedical practitioners dealing with pelvic floor dysfunction. There is an obvious need for research into the mitigation of pelvic floor morbidity, which results in over 200 000 surgical procedures per year in the United States alone3. It now appears that we may have missed the forest for the trees. We have overlooked a form of maternal birth trauma that occurs commonly during crowning of the fetal head, about once a day in an obstetric unit catering for a few thousand deliveries per year. Occasionally, it can be detected visually if it is combined with a vaginal tear, or, if occult, it can be detected by palpation and imaging (Figure 1). I acknowledge that this seems hard to believe. The problem should have been solved in the late 1900s, rather than being left to us. Why did it take obstetricians so long to detect a problem that must have been there forever – that is, ever since hominids assumed an upright posture and developed this peculiar compromise that is the levator ani muscle complex of Homo sapiens? In fact, delivery-related levator trauma was detected a long time ago. In 1907, Halban and Tandler published a monograph in Vienna1 that is still regarded as the finest achievement in pelvic floor anatomy by many working in this field. In this monograph on pelvic organ prolapse they describe, on Page 191, almost complete loss of the anteromedial aspects of the levator ani muscle in women with prolapse, and they put the blame squarely on childbirth, implying intrapartum trauma. In 1943, Howard Gainey, a general obstetrician from Kansas City, published data on a series of 1000 women who he had examined for pelvic floor trauma after vaginal delivery11. He confirmed his observation in another paper 12 years later12. Gainey described an incidence of trauma to the pubococcygeus muscle of approximately 20–30% in primiparous women, with a preponderance of rightsided trauma – exactly as we are observing today with the help of modern imaging methods13–16. Gainey used his fingers – but it is obvious that the digital detection of pelvic floor trauma, while possible, is not easy and requires significant training17,18. This may be one of the reasons that his publications had little, if any, impact. Another may be that he ended up advocating universal forceps and episiotomy, which is difficult to understand when, on biomechanical grounds, both may be risk factors for levator trauma, rather than being protective; forceps delivery definitely seems to be associated with increased levator trauma10,15. So Gainey probably drew the wrong conclusions, but his clinical findings are vindicated now, over