What is the significance of the head-to-body delivery interval in ...

What is the significance ofthe head-to-body delivery intervalin shoulder dystocia?A longer interval may be more likely to lead to persistentbrachial plexus injury and neonatal depression, according to thisobservational case-control analysis.The median intervalfrom head-to-bodydelivery inuncomplicated birthswas 1.0 minute,compared with2.0 minutes for birthscomplicated bybrachial plexuspalsy alone, and5.3 minutes for birthscomplicated by bothbrachial plexus palsyand neonataldepressionLerner H, Durlacher K, Smith S, Hamilton E. Relationshipbetween head-to-body delivery interval in shoulder dystociaand neonatal depression. Obstet Gynecol. 2011;118(2 Pt1):318–322.}expert commentaryWilliam A. Grobman, MD, MBA, Associate Professorof Obstetrics and Gynecology, Feinberg School ofMedicine, Northwestern University, Chicago, Ill.Shoulder dystocia is a well-describedobstetric complication that occurs inapproximately 1% of deliveries. 1 It has beenassociated with adverse maternal outcomesas well as adverse perinatal outcomes,including fracture, nerve palsy, and hypoxicischemic encephalopathy.Although multiple risk factors for shoulderdystocia have been described, expertshave not yet been able to combine theminto an accurate, discriminating, clinicallyuseful shoulder dystocia prediction model;therefore, shoulder dystocia remains anunpredictable event. 2 We also lack a strategyto prevent shoulder dystocia. Becausewe cannot predict or prevent it, a provider’sresponse to shoulder dystocia, once it occurs,is seminal, in terms of management.Details of the studyAs Lerner and colleagues concisely state,when shoulder dystocia occurs, there is aneed for caution in the application of forceduring maneuvers and a “countervailingneed to achieve delivery.” It is in a provider’sinterest, then, to have knowledge of whetherthere is a time at which that countervailingneed to achieve delivery takes on greater relativesignificance.In an effort to address this issue, theauthors examined the relationship betweenthe duration of shoulder dystocia and neonataldepression (defined as the need for cardiopulmonaryresuscitation or intubation; apH level below 7.0; an Apgar score below 6 at5 minutes; or death).In their study, 127 births involvinguncomplicated shoulder dystocia (i.e., noevidence of neonatal trauma or depression)from a single institution were comparedwith 55 births involving complicated shoulderdystocia (i.e., the occurrence of brachialplexus palsy with or without neonataldepression).Lerner and colleagues found a correlationbetween the duration of shoulderdystocia and the extent of neonatal complications.For example, the medianinterval from head-to-body delivery foruncomplicated births was 1.0 minute;for births complicated by brachial plexuspalsy alone, it was 2.0 minutes; and forbirths complicated by brachial plexus palsyand neonatal depression, the interval was5.3 minutes (P

Strengths and weaknessesof the trialAs the authors note, one limitation of theirstudy is a lack of precision in the recordedduration of shoulder dystocia cases, giventhat “it appears that clinicians often rounded”the stated times.Other types of bias that may have affectedthe findings include:• Selection bias. In an observational studysuch as this, it is typically ideal to draw thecases and controls from the same underlyingpopulation in an effort to limit theoccurrence of other potentially confoundingfactors, both known and unknown. Inthis study, however, the uncomplicatedcases came from one institution over10 years, whereas the complicated casescame from a medicolegal database oneauthor had accumulated over 15 years.Because these clearly are very differentpopulations, the reported associationbetween head-to-body delivery intervaland brachial plexus palsy or neonataldepression may be related to characteristicsother than, or in addition to, durationof the dystocia. For example, there mayhave been complicated cases that did notresult in legal action. If the duration of thedystocia is in any way related to the chancethat medicolegal action occurs, the relationshipbetween duration and the presenceof complication will be affected.• Ascertainment bias. Because this studylacked a standard approach to the recordingof duration, ascertainment bias mayhave affected the results. It is possible,for example, that the knowledge that acomplication did or did not occur couldhave affected whether the duration wasrecorded or how much time was documented.What this evidence meansfor practiceThe data published to date, 3,4 includingthis study, should offer some reassuranceto obstetric care providers. Longtermadverse outcomes are uncommonin shoulder dystocia. Even intermediateoutcomes such as neonatal depression,when they do occur, appear to beuncommon when the shoulder dystocia isof relatively short duration.When shoulder dystocia does occur,however, providers should maintainsituational awareness, being cognizantof the time that elapses, so that the continuationof appropriate and coordinatedmaneuvers can be ensured.››William A. Grobman, MD, MBAComplications of shoulderdystocia are rareUltimately, the primary question posed inthis article is difficult to answer. Althoughshoulder dystocia occurs in approximately1% of births, major adverse perinatal outcomesoccur in only a fraction of these cases.That fact means that an event such as permanentbrachial plexus palsy or neonataldepression, let alone actual hypoxic ischemicencephalopathy, occurs only in the context ofthousands of births.References1. Gherman RB. Shoulder dystocia: an evidence-basedevaluation of the obstetric nightmare. Clin Obstet Gynecol.2002;45(2):345–362.2. Grobman WA, Stamilio DM. Methods of clinical prediction.Am J Obstet Gynecol. 2006;194(3):888–894.3. Allen RH, Rosenbaum TC, Ghidini A, Poggi SH, Spong CY.Correlating head-to-body delivery intervals with neonataldepression in vaginal births that result in permanent brachialplexus injury. Am J Obstet Gynecol. 2002;187(4):839–842.4. Leung TY, Stuart O, Sahota DS, Suen SS, Lau TK, LaoTT. Head-to-body interval and risk of fetal acidosis andhypoxic ischaemic encephalopathy in shoulder dystocia: aretrospective review. BJOG. 2011;118(4):474–479.Although shoulderdystocia occurs inapproximately 1% ofbirths, major adverseperinatal outcomesoccur in only afraction of thesecasesDid you see this related article?Does the use of multiple maneuvers in the managementof shoulder dystocia increase the risk of neonatal injury?Robert B. Gherman, MD (Examining the Evidence, August 2011)Find it in the archive at obgmanagement.comobgmanagement.com Vol. 23 No. 12 | December 2011 | OBG Management 51