New directions in understanding how the pelvic floor prepares for and recovers from vaginal delivery
2015; Elsevier BV; Volume: 213; Issue: 2 Linguagem: Inglês
10.1016/j.ajog.2015.05.016
ISSN1097-6868
Autores Tópico(s)Pelvic and Acetabular Injuries
ResumoSee related articles, pages 188 and 191 See related articles, pages 188 and 191 Depending on your view, physicians who medicalize childbirth are either saints or sinners—saints for saving lives or sinners for turning a natural process into an unnatural one. Nearly a century ago, Joseph DeLee1DeLee J.B. The prophylactic forceps operation.Am J Obstet Gynecol. 1920; 1: 24-44Google Scholar likened the process of vaginal delivery to that of the mother falling on a pitchfork and driving the handle through her perineum. His recommendation to use episiotomy and forceps to protect both mother and baby became applied routinely. Decades later, it became apparent that both routine episiotomy and forceps deliveries caused more harm than good in terms of the pelvic floor.2Carroli G. Mignini L. Episiotomy for vaginal birth.Cochrane Database Syst Rev. 2009; 1: CD000081PubMed Google Scholar, 3Volløyhaug I. Mørkved S. Salvesen Ø. Salvesen K.Å. Forceps is associated with increased risk of pelvic organ prolapse and muscle trauma: a cross-sectional study 16-24 years after first delivery.Ultrasound Obstet Gynecol. 2015; ([Epub ahead of print])PubMed Google Scholar Cesarean delivery, which was used initially to save lives, is chosen increasingly to save women from purported ravages of pelvic floor disorders and sexual dysfunction.4D'Souza R. Caesarean section on maternal request for non-medical reasons: putting the UK National Institute of Health and Clinical Excellence guidelines in perspective.Best Pract Res Clin Obstet Gynaecol. 2013; 27: 165-177Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar Yet, similar to the episiotomy and forceps recommended by DeLee, this ultimate medicalization of childbirth has unintended consequences as providers caught in an epidemic of hemorrhage related to abnormal placentation can attest. That women delivered by cesarean are less likely to have pelvic organ prolapse in the future is well documented.3Volløyhaug I. Mørkved S. Salvesen Ø. Salvesen K.Å. Forceps is associated with increased risk of pelvic organ prolapse and muscle trauma: a cross-sectional study 16-24 years after first delivery.Ultrasound Obstet Gynecol. 2015; ([Epub ahead of print])PubMed Google Scholar But that cesarean delivery is the only intervention in our armamentarium to decrease childbirth-related pelvic floor morbidity strikes me as a failure of imagination. What if we thought about vaginal delivery as sports medicine physicians think about other soft tissue injuries that are sustained in the course of strenuous activity? We would then focus research on fully understanding what structures are injured, how they can be repaired, and how we can improve the recovery process. Given that the demand for care for pelvic floor disorders is projected to increase by 35% between 2010 and 2030,5Kirby A.C. Luber K.M. Menefee S.A. An update on the current and future demand for care of pelvic floor disorders in the United States.Am J Obstet Gynecol. 2013; 209: 584.e1-584.e5Abstract Full Text Full Text PDF Scopus (55) Google Scholar the elimination of even a small proportion of disorders caused in part by childbirth would have a large impact. Two research studies in this month's Journal provide needed information about maternal recovery after vaginal delivery. Miller et al6Miller J. Low K.L. Zielinski R. Smith A. DeLancey J. Brandon C. Evaluating maternal recovery from labor and delivery: bone and levator ani injuries.Am J Obstet Gynecol. 2015; 213: 188.e1-188.e11Abstract Full Text Full Text PDF PubMed Scopus (45) Google Scholar use data from the Evaluating Maternal Recovery from Labor and Delivery study to demonstrate women's recuperative powers after delivery. Participants had at least 1 risk factor for levator ani muscle injury, as established by previous research: a long second stage, anal sphincter tear, or older maternal age. They underwent an innovative musculoskeletal magnetic resonance scan with fluid-sensitive sequences 7 weeks and 8 months after delivery. Seven weeks after delivery, 91% of women showed some form of musculoskeletal injury that involved the pubic bone or levator ani muscle: 66% had pubic bone marrow edema; 29% had pubic subcortical fracture; 90% had levator muscle edema, and 41% had low-grade or greater levator ani muscle tear. Although, as expected, the magnitude of levator muscle tear did not change substantially, the muscle edema and bony injuries resolved almost completely in most women. The 4 women with persistent levator ani edema at 8 months had each sustained a high-grade levator ani muscle tear. Thus, using methods created for evaluation of sports-related injuries, the investigators furthered our understanding of recovery after an arguably more common soft tissue injury—vaginal delivery. I am sure you have wondered how the pelvic floor muscle manages to stretch to over 3 times its usual length to allow egress of the fetal head.7Hoyte L. Damaser M.S. Warfield S.K. et al.Quantity and distribution of levator ani stretch during simulated vaginal childbirth.Am J Obstet Gynecol. 2008; 199: 198.e1-198.e5Abstract Full Text Full Text PDF PubMed Scopus (85) Google Scholar, 8Lien K.C. Mooney B. DeLancey J.O. Ashton-Miller J.A. Levator ani muscle stretch induced by simulated vaginal birth.Obstet Gynecol. 2004; 103: 31-40Crossref PubMed Scopus (318) Google Scholar Even in the most flexible of women, no other muscle in the body can do this. That 70-85% of the time the pelvic floor muscles can stretch so far without tearing is a testament to the power of this natural system. In this month's Journal, Alperin et al9Alperin M. Lawley D.M. Esparza M.C. Lieber R.L. Pregnancy induced adaptations in the intrinsic structure of rat pelvic floor muscles.Am J Obstet Gynecol. 2015; 213: 191.e1-191.e7Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar used a rat model to elucidate part of how this is possible.9Alperin M. Lawley D.M. Esparza M.C. Lieber R.L. Pregnancy induced adaptations in the intrinsic structure of rat pelvic floor muscles.Am J Obstet Gynecol. 2015; 213: 191.e1-191.e7Abstract Full Text Full Text PDF PubMed Scopus (41) Google Scholar Beginning in midpregnancy and continuing through the gestational period, the normalized fiber length of the pelvic floor muscles increased by 21-37% (no change was seen in the tibialis anterior, which was used as a control). This happened because the number of sarcomeres in a series actually increased. Although there was no change in either the cross-sectional area of the muscles or in the length of the sarcomeres, the quantity of extracellular matrix inside the pelvic floor muscles increased by 140% in the coccygeus muscle at late pregnancy (and again, was unchanged in the tibialis anterior). The normalized fiber length then decreased after delivery and, by 12 weeks, was similar to that of virgin rats. However, the extracellular collagen matrix content of the coccygeus muscle remained significantly higher than that of virgin controls, even at 12 weeks. The authors note that increased fiber length is protective against muscle injury because large mechanical deformations are distributed across a greater number of sarcomeres. That the increased extracellular collagen matrix may shield the muscle fibers from excessive mechanical strain during delivery by providing a parallel elastic element that limits fiber strain. Similar to findings in these rats, nascent research in humans also indicates that adaptations that enable vaginal delivery appear to begin long before delivery.10Oliphant S.S. Nygaard I.E. Zong W. Canavan T.P. Moalli P.A. Maternal adaptations in preparation for parturition predict uncomplicated spontaneous delivery outcome.Am J Obstet Gynecol. 2014; 211: 630.e1-630.e7Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar These studies raise many intriguing questions that, once answered, may open the door to new preventive strategies. Can we affect fiber strain during pregnancy and thereby decrease the magnitude of muscle injury? Can we favorably influence other pregnancy-induced adaptations to minimize pelvic floor trauma? Do adaptations or recovery differ in those with predisposition genes for pelvic organ prolapse? What factors might enhance postpartum pelvic floor recovery? Should certain activities be minimized or maximized during the acute healing phase of recovery? What can we learn from the majority of women who do not demonstrate pelvic floor injury after vaginal delivery? DeLee's1DeLee J.B. The prophylactic forceps operation.Am J Obstet Gynecol. 1920; 1: 24-44Google Scholar pitchfork analogy suggests a violent, irreparable, explosive injury. Although this analogy fits a small minority of women who experience devastating urinary and fecal incontinence and pelvic organ prolapse immediately after their first delivery, the research presented in this month's Journal suggests that a bendy person toy would be a better (and certainly more gentle!) analogy with which to think about pelvic floor changes during uncomplicated vaginal delivery. With a more perfect understanding of how pregnancy and delivery impact the structure and function of pelvic floor structures comes the opportunity for preventive strategies heretofore unconsidered. Pregnancy-induced adaptations in the intrinsic structure of rat pelvic floor musclesAmerican Journal of Obstetrics & GynecologyVol. 213Issue 2PreviewMaternal birth trauma to the pelvic floor muscles (PFMs) is a major risk factor for pelvic floor disorders. Modeling and imaging studies suggest that demands placed on PFMs during childbirth exceed their physiologic limits; however many parous women do not sustain PFM injury. Here we determine whether pregnancy induces adaptations in PFM architecture, the strongest predictor of muscle function, and/or intramuscular extracellular matrix (ECM), responsible for load bearing. To establish if parallel changes occur in muscles outside of the PFM, we also examined a hind limb muscle. Full-Text PDF Evaluating maternal recovery from labor and delivery: bone and levator ani injuriesAmerican Journal of Obstetrics & GynecologyVol. 213Issue 2PreviewWe sought to describe occurrence, recovery, and consequences of musculoskeletal (MSK) injuries in women at risk for childbirth-related pelvic floor injury at first vaginal birth. Full-Text PDF
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