http://informahealthcare.com/jmf ISSN: 1476-7058 (print), 1476-4954 (electronic) J Matern Fetal Neonatal Med, Early Online: 1–5 ! 2014 Informa UK Ltd. DOI: 10.3109/14767058.2014.972925
ORIGINAL ARTICLE
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Asynclitism: a literature review of an often forgotten clinical condition Antonio Malvasi1,2, Antonio Barbera3,4, Giovanni Di Vagno5, Alexis Gimovsky6, Vincenzo Berghella6, Tullio Ghi7, Gian Carlo Di Renzo8, and Andrea Tinelli2,9 1
Department of Gynecology and Obstetric, Santa Maria Hospital, Bari, Italy, 2Department of Applied Mathematics, Moscow Institute of Physics and Technology (State University), International Translational Medicine and Biomodelling Research Group, Moscow, Russian Federation, 3Banner Health Clinic, Ob-Gyn Department, North Colorado Medical Center, Greeley, CO, USA, 4School of Medicine, University of Denver, Aurora, CO, USA, 5 Department of Obstetric & Gynecology, Umberto I Hospital, Corato-Terlizzi, Bari, Italy, 6Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Jefferson Medical College of Thomas, Jefferson University, Philadelphia, PA, USA, 7Department of Obstetric & Gynecology, Policlinico S.Orsola-Malpighi, Bologna, Italy, 8Department of Obstetric & Gynecology and Centre for Perinatal and Reproductive Medicine, Santa Maria della Misericordia University Hospital, Perugia, Italy, and 9Department of Gynecology and Obstetrics, Vito Fazzi Hospital, Lecce, Italy, Lecce, Italy Abstract
Keywords
Asynclitism is defined as the ‘‘oblique malpresentation of the fetal head in labor’’. Asynclitism is a clinical diagnosis that may be difficult to make; it may be found during vaginal examination. It is significant because it may cause failure of progress operative or cesarean delivery. We reviewed all literature for asynclitism by performing an extensive electronic search of studies from 1959 to 2013. All studies were first reviewed by a single author and discussed with coauthors. The following studies were identified: 8 book chapters, 14 studies on asynclitism alone and 10 papers on both fetal occiput posterior position and asynclitism. The fetal head in a laboring patient may be associated with some degree of asynclitism; this is seen as usual way of the fetal head to adjust to maternal pelvic diameters. However, marked asynclitism is often detected in presence of a co-existing fetal head malposition, especially the transverse and occipital posterior positions. Digital diagnosis of asynclitism is enhanced by intrapartum ultrasound with transabdominal or transperineal approach. The accurate diagnosis of asynclitism, in an objective way, may provide a better assessment of the fetal head position that will help in the correct application of vacuum and forceps, allowing the prevention of unnecessary cesarean deliveries.
Asynclitism, birth canal, cesarean section, delivery, fetal head, malposition, obstructed labor, occiput position, pelvis
Introduction Synclitism of the fetal head is the specific condition in which neither of the parietal bones precedes the sagittal suture into the maternal birth canal. Another definition of synclitism is ‘‘a condition in which the sagittal suture of the fetal head is in line with the transverse diameter of the inlet, equidistant from the maternal symphysis pubis and sacrum’’ [1]. This position is usually detected during vaginal examination, either in late pregnancy or in early labor, when the fetal head enters the pelvic inlet [1]. The absence of synclitism; when one of the parietal bone preceds the sagittal suture is called asynclitism. The one of the earliest documented descriptions of asynclitism, called ‘‘anterior obliquity’’ was presented by Franz Karl Na¨gele in his book published in 1842 [2]. In 1871, Carl Conrad Theodor Litzmann reported the ‘‘posterior
Address for correspondence: Dr. Andrea Tinelli, MD, Department of Gynecology and Obstetrics, Vito Fazzi Hospital, P.zza Muratore, Lecce 73100, Italy. E-mail: [email protected]
History Received 23 June 2014 Revised 1 October 2014 Accepted 1 October 2014 Published online 29 October 2014
obliquity’’ described below as posterior asynclitism [3]. In 1885, Smith described the protuberance of the right parietal bone, after delivery, as ‘‘obliquity of the head’’ [4], while other authors reported asynclitism especially when it was associated with fetal complications [5]. The etymology of asynclitism derives from an ancient Greek word, i.e. Gk, a + syn, not together, kleisis, to lean [6]. In almost any normal labor, the fetal head engages the maternal pelvis with a certain degree of asynclitism. When the anterior parietal bone precedes the sagittal suture, there is an anterior asynclitism (Na¨gele obliquity), whereas if the posterior parietal bone precedes the sagittal suture, there is a posterior asynclitism (Litzmann obliquity) [7,8]. Asynclitism is also defined as the ‘‘oblique malpresentation of the fetal head in labor’’ [9]. Figure 1 shows a vaginal examination in the case of posterior asynclitism in a left occiput transverse position. The first step in the diagnosis of asynclitism is the assessment of the fetal occiput in relationship to the maternal pelvis. Any position of the fetal head, i.e. anterior, transverse and posterior, both left or right, may show a peculiar type of asynclitism (Table 1). In case of anterior
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Figure 1. Sterile vaginal examination. Fetal head is in left occiput transverse position with posterior asynclitism. The sagittal suture is palpated closer to the symphysis.
Table 1. Different type of asynclitism in each vertex presentation.
J Matern Fetal Neonatal Med, Early Online: 1–5
Asynclitism, especially if marked, is frequently associated with the occiput posterior position [11], but it can be diagnosed in the occiput anterior, right and left, posterior and transverse positions [7]. Asynclitism is usually considered as a physiological part of the birth process, by which the fetal head engages and progresses in the birth canal. When entering the pelvis at the level of the inlet, the fetus is not lying in a perfectly vertical position. Furthermore, a woman’s pelvis is often tilted as well. [9] At the time of a digital examination during labor, identification of the sagittal suture occurs. The sagittal suture will usually be parallel to the largest diameters of the pelvis: the oblique diameter at the inlet and the antero– posterior at the mid and lower pelvis. The next step will be the identification of the anterior or posterior fontanelles, diagnosing the orientation of the occiput in the maternal pelvis, i.e. anterior, posterior, left, right, transverse. Only after the identification of a specific fetal landmark in the maternal pelvis, either the anterior or posterior fontanel, that the correct diagnosis of asynclitism can be made. In cases of minor asynclitism and molding of the fetal head, a safe vaginal delivery, spontaneous or operative, can often be accomplished [11]. However, in the patient with a difficult vaginal examination, as in the presence of excessive molding and caput or occiput posterior and transverse positions, clinical diagnosis may be difficult. Many of these cases are failure to labor progress that need to be resolved with operative vaginal or cesarean delivery [12].
Review of asynclitism literature
asynclitism, the more prominent parietal bone is the one on the opposite side to which the head is rotated towards, whereas in posterior asynclitism the more prominent parietal bone is the one on the same side to which the head is rotated towards. For example, in left occiput position, anterior asynclitism is diagnosed when the right parietal bone is more prominent, whereas posterior asynclitism is diagnosed when the left parietal bone is more prominent. This concept is applicable regardless of the occiput being positioned anteriorly, posteriorly, or transverse.
Asynclitism rates in labor In the literature it is reported that the occiput posterior position is the most common malposition of the fetal head during labor. It occurs in 10–30% of fetuses in the first stage of labor, but most cases resolves spontaneously [10].
Pubmed, Medline, Embase, CINAHL PlusÕ , Web of Science Reference, Scopus, Science Direct and Cochrane Databases online databases were searched, using ‘‘asynclitism’’ as the keyword. Only 14 studies were identified. The word ‘‘asynclitism’’ was reported also in obstetrics books, dictionaries, monographs, and guidelines. The terminology, definitions, and classifications used are the same as those used in the 19th century and early 20th centuries. So, the question that comes spontaneously is why are there so few asynclitism studies in the obstetric literature? There may be various reasons for this. First, there is variability in the definition of asynclitism, its diagnosis and the subsequent obstetric outcomes [13]. A second reason may be that many researchers feel that asynclitism is a normal phenomenon of labor; they consider it to be non-concerning until its degree is so marked that it becomes responsible for a prolonged or obstructed labor. Another possible cause is that with today’s reduction in operative vaginal deliveries, both via forceps or vacuum, and the increase of cesarean deliveries, that this negates the need for an accurate diagnosis of asynclitism. Approximately 5% of all deliveries in the United States are operative vaginal deliveries (1 in 20); the past 20 years have seen a progressive shift away from the use of forceps in favor of the vacuum extractor as the device of choice [14]. The study of Bofil et al. [15] evaluated asynclitism and vaginal operative delivery and concluded that the M-cup
DOI: 10.3109/14767058.2014.972925
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vacuum extractor cup appears to be as efficient (and faster) than forceps, but is associated with significantly more fetal cephalohematomas, whereas maternal injuries are more common when using forceps. Digital vaginal examination has limitations in the diagnosis of asynclitism during the second labor stage. Additionally, at time of delivery, a common sign of asynclitism is a molded or misshapen infant head in parietal zone [8,9]. It has been only since the recent use of ultrasound during labor that new objective signs for the diagnosis of asynclitism have been described [16].
Clinical evaluation: accuracy and limits Sherer [17] demonstrated an overall high rate of error (76%) when fetal head position was assessed in active labor by digital examination compared with diagnosis performed by ultrasound. The jigh rate of error of digital examination persisted (65%) in the second stage of labor, independent of years of clinical experience. (senior residents versus full trained physicians). Uguwumadu et al. [18] reported that in dystocic labor, the presence of the caput succedaneum or scalp hair, especially with associated asynclitism, was responsible for the large error of the digital examination, in a percentage even greater than that reported by Sherer [17,19].
Intrapartum sonography and new diagnosis tools The use of intrapartum ultrasound has been shown to increase the accuracy of detecting abnormal fetal head positions during the second stage of labor [18]. Furthermore, ultrasound has been recently used as a more objective tool in supporting and validating the clinical diagnosis of asynclitism. Different ultrasonographic approaches including transabdominal, transperineal and transvaginal, usually in 2D, have been utilized in the determination of fetal position, using specific fetal landmarks like orbits, cerebellum, midline echo of the brain and
Figure 2. Left occiput posterior position, with anterior asyncitism. Only the anterior orbit is visualized by ultrasound, as the ‘‘squint sign’’ [18] (panel A: graphic representation; panel B: transbdominal ultrasound used up to the beginning of the second stage of labor, with the ‘‘squint sign’’).
A review on asynclitism in modern obstetrician
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occiput. Ghi et al. [20], have used a 3-D probe for the diagnosis of asynclitism. In making an ultrasonographic diagnosis of asynclitism, Sherer [17] affirmed: ‘‘of note, we find asynclitism may be appreciating subjectively an indirect fashion when difficulty is encountered in depicting symmetrically positioned midline fetal intracranial structure’’. This may lead the operator to use an acute angle of the ultrasound transducer by the operator (in either maternal cephalic or maternal caudal directions) in order to capture the optimal symmetric fetal intracranial image. In the absence of well-depicted maternal structures (symphysis pubis or sacral promontory), the appreciation of asynclitism is very limited. Asynclitism can also be easily diagnosed by ultrasound in occiput posterior position by transabdominal ultrasound. Diagnosis is based on the observation of only a single orbit instead of two, the so-called ‘‘the squint sign’’ (Figures 2 and 3) [9,16]. This sign is confirmed also with translabial sonography in both sagittal and transverse plane, identifying the midline intracranial structures and asymmetry of the cerebellum and the thalamus. An objective diagnosis of asynclitism can also be achieved in case of occiput tranverse position (Figure 4). An early diagnosis of persistent transverse position may allow a more objective management of labor. Uncertainty in clinical assessment of fetal position prior to an operative vaginal delivery, noted in up to 25% of cases, has been objectively improved by the use of intrapartum ultrasound [21]. Our group described two signs for diagnosing asynclitism: the ‘‘squint sign’’ and the ‘‘sunset of thalamus and cerebellum signs’’ [22]. These are two simple ultrasonographic signs allowing detection of anterior and posterior asynclitism. One proposed mechanism for malposition during labor is epidural anesthesia. Labor with low-dose epidural analgesia does not increase the incidence of occipital posterior position, transverse position or asynclitism [23,24]. Transverse fetal head positioning with anterior or posterior asynclitism does
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J Matern Fetal Neonatal Med, Early Online: 1–5
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Figure 3. Right occiput posterior position, with anterior asyncitism (with the ‘‘squint sign’’ in ultrasonographic image).
Figure 4. A left occiput tranverse position (panel A: graphic representation; panel B: transbdominal ultrasound used up to the beginning of the second stage of labor, showing the ‘‘sunset of thalamus and cerebellum signs’’).
not seem to be promoted by drug or technique-related mechanisms, but rather could be the consequence of cephalopelvic disproportion [24,25]. Another way to diagnose asynclitism by ultrasound is with the visualization of the fontanels and sutures. Dikkeboom et al. [26] reported that 3D ultrasound can be a reliable technique for visualizing most fetal cranial sutures and fontanelles. Utilizing sagittal and transverse scans, most of the sutures and fontanels can be visible during the second half of pregnancy. Fuchs et al. [27] showed various images of fetal sutures and fontanelles obtained by 3D ultrasound during labor. The conclusion was that, once the technical difficulties involved in its intrapartum use, 3D ultrasound may be indicated for the determination of the fetal head position in the birth canal in particular for the diagnosis of asynclitism.
Conclusions The presence of asynclitism can frequently be responsible for arrest of labor, and its missed diagnosis may contribute to suboptimal intrapartum management. Even in the presence of
a normal size pelvis [7–9]. Moreover, asynclitism is often associated with other malpositions, especially the transverse and the occipital posterior positions [11,28]. Currently, there are only a few studies on this important clinical entity, indicating a clear need for prospective multicenter randomized trials. Intrapartum sonography has been shown to be of a great help in the diagnosis of asynclitism compared to the more subjective digital examination. Since among the reasons for failure of the vacuum extractor are the occiput posterior position, asynclitism, and uncertain position of the fetal head (a contraindication for operative vaginal delivery) [29], it is important to emphasize that the correct diagnosis of any of these malpositions performed by ultrasound may improve outcomes [21]. The ultrasound diagnosis of occiput posterior position and asynclitism is an objective assessment, and its repercussion is of paramount importance. Increased awareness of the possibility of asynclitism and its correction could significantly decrease the incidence of primary cesarean section [30]. Furthermore, it could be important for correct documentation, for better use of CPT codes and for objective support in cases
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DOI: 10.3109/14767058.2014.972925
with bad outcomes and consequent legal litigation. Diagnosis of asynclitism performed by ultrasound is not meant to replace the digital vaginal exam, but its purpose is to support the diagnosis and improve the management of the second stage of labor. This should encourage physicians to introduce clinical ultrasound examination into their daily practice for the diagnosis and documentation of head malposition and asynclitism [20,22]. Awareness of this very specific obstetric entity is valuable during both the first and the second stage of labor. If diagnosed early, the provider managing labor will be supported in having a more expectant management, whereas if diagnosis is made during the second stage of labor, it will help in making a decision on which route of delivery to choose.
Declaration of interest The authors declare no conflicts of interests. The authors alone are responsible for the content and writing of this article.
References 1. Mosby’s Medical Dictionary, 8th ed. St Louis,. MO: Elsevier; 2009. 2. Nagele FK. Lehrbuch der Geburtshu¨lfe fu¨r Hebammen. Heidelberg: J.C.B. Mohr; 1842. 3. Litzmann CCT. Uber die hintere scheitelbeineinstellung, eine nitch seltene Art der fehlerhaften Einstellung des Koppfelsunter delGeburth Arch.f.Geb.u. Gyn, Vol.XLVIII; 1871. 4. Smith WT. The mechanism of labor. In: A manual of obstetrics: theoretical and practical. Chapter XXII. Chandon Street London: Savill and Edwards. Printers; 1858:265–82. 5. Siciliano G, Marchiafava G. Asynclitic ventral shoulder presentation; two cases with deflection and epidural hemorrhage. Monit Ostet Ginecolog 1952;23:233–55. 6. Farlex Partner Medical Dictionary. Farlex; 2012. 7. Akmal S, Peterson Brown S. Malpositions and malpresentations of foetal head. Obstet Gynecol Reprod Med 2009;19:240–6. 8. Kilpatric S, Garrison E. Normal labor and delivery. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics normal and problem pregnancies, 5th ed., vol 12. Philadelphia (PA): Churcill Livingstone Elsevier; 2007:307–8. 9. Barbera AF, Tinelli A, Malvasi A. Asynclitism: clinical and intrapartum diagnosis in labor. In: Malvasi A, ed. Intrapartum ultrasonography for labor management, Vol. 6. Heidelberg: Springer-Verlag; 2013:73–86. 10. Simkin P. The fetal occiput posterior position: state of the science and a new perspective. Birth 2010;37:61–71. 11. Malvasi A, Tinelli A, Barbera A, et al. Occiput posterior position diagnosis: vaginal examination or intrapartum sonography? A clinical review. J Matern Fetal Neonatal Med 2013 Sep 13. 2014;27:520–6. 12. McQuivey RW. Vacuum-assisted delivery: a review. J Matern Fetal Neonatal Med 2004;16:171–80.
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13. Dupuis O, Ruimark S, Corinne D, et al. Fetal head position during the second stage of labor: comparison of digital vaginal examination and transabdominal ultrasonographic examination. Eur J Obstet Gynecol Reprod Biol 2005;123:193–7. 14. Ali UA, Norwitz ER. Vacuum assisted vaginal delivery. Rev Obstet Gynecol 2009;21:5–17. 15. Bofill JA, Rust OA, Schorr SJ, et al. A randomized prospective trial of obstetric forceps versus the M-cup vacuum extractor. Am J Obstet Gynecol 1996;175:1325–30. 16. Malvasi A, Tinelli A, Stark M. Intrapartum sonography sign for occiput posterior asynclitism diagnosis. J Matern Fetal Neonatal Med 2011;24:553–4. 17. Sherer DM, Miodovnik M, Bradley KS, Langer O. Intrapartum fetal head position I: Comparison between transvaginal digital examination and transabdominal ultrasound assessment during the active stage of labour. Ultrasound Obstet Gynecol 2002;19:258–63. 18. Ugwumadu A. The role of ultrasound scanning on the labor ward. (Opinion). Ultrasound Obstet Gynecol 2002;19:222–4. 19. Sherer DM, Miodovnik M, Bradley KS, Langer O. Intrapartum fetal head position II: comparison beetween transvaginal digital examination and transabdominal ultrasound assessment during the second stage of labour. Ultrasound Obstet Gynecol 2002;19:264–8. 20. Ghi T, Youssef A, Pilu G, et al. Intrapartum sonographic imaging of fetal head asynclitism. Ultrasound Obstet Gynecol 2012;39:238–40. 21. Ali UA, Norwitz ER. Vacuum-assisted vaginal delivery. Rev Obstet Gynecol 2009;2:5–17. 22. Malvasi A, Stark M, Ghi T, et al. Intrapartum sonography for fetal head asynclitism and transverse position: sonographic signs and comparison of diagnostic performance between transvaginal and digital examination. J Matern Fetal Neonatal Med 2012; 25:508–12. 23. Malvasi A, Tinelli A, Brizzi A, et al. Intrapartum sonography head transverse and asynclitic diagnosis with and without epidural analgesia initiated early during the first stage of labor. Eur Rev Med Pharmacol Sci 2011;15:518–23. 24. Malvasi A, Tinelli A, Brizzi A, et al. Intrapartum sonography for occipito posterior detection in early low dose combined spinal epidural analgesia by sufentanyl and ropivacaine. Eur Rew Med Pharmacol Sci 2010;14:799–806. 25. Akmal S, Tsoi E, Howard R, et al. Investigation of occiput posterior delivery by intrapartum sonography. Ultrasound Obstet Gynecol 2004;24:425–8. 26. Dikkeboom CN, Roelfsema NM, Van Adrichem LN, Wladimiroff JW. The role of three-dimensional ultrasound in visualizing the fetal cranial sutures and fontanels during the second half of pregnancy. Ultrasound Obstet Gynecol 2004;24:412–6. 27. Fuchs I, Tutschek B, Henrich W. Visualization of the fetal fontanels and Skull by three-dimensional translabial ultrasound during the second stage of labor. Ultrasound Obstet Gynecol 2008;31:484–6. 28. Barbera AF, Tinelli A, Pacella E, Malvasi A. Occiput posterior position and intrapartum sonography. In: Malvasi A, ed. Intrapartum ultrasonography for labor management, Vol. 5. Heidelberg: Springer-Verlag; 2013:61–72. 29. Rozenberg P, Porcher R, Salomon LJ, et al. Comparison of the learning curves of digital examination and transabdominal sonography for the determination of fetal head position during labor. Ultrasound Obstet Gynecol 2008;31:332–7. 30. Operative vaginal delivery. Royal College of Obstetric & Gynecology, Greentop guideline n 26; 2011.
ORIGINAL ARTICLE
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Asynclitism: a literature review of an often forgotten clinical condition Antonio Malvasi1,2, Antonio Barbera3,4, Giovanni Di Vagno5, Alexis Gimovsky6, Vincenzo Berghella6, Tullio Ghi7, Gian Carlo Di Renzo8, and Andrea Tinelli2,9 1
Department of Gynecology and Obstetric, Santa Maria Hospital, Bari, Italy, 2Department of Applied Mathematics, Moscow Institute of Physics and Technology (State University), International Translational Medicine and Biomodelling Research Group, Moscow, Russian Federation, 3Banner Health Clinic, Ob-Gyn Department, North Colorado Medical Center, Greeley, CO, USA, 4School of Medicine, University of Denver, Aurora, CO, USA, 5 Department of Obstetric & Gynecology, Umberto I Hospital, Corato-Terlizzi, Bari, Italy, 6Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Jefferson Medical College of Thomas, Jefferson University, Philadelphia, PA, USA, 7Department of Obstetric & Gynecology, Policlinico S.Orsola-Malpighi, Bologna, Italy, 8Department of Obstetric & Gynecology and Centre for Perinatal and Reproductive Medicine, Santa Maria della Misericordia University Hospital, Perugia, Italy, and 9Department of Gynecology and Obstetrics, Vito Fazzi Hospital, Lecce, Italy, Lecce, Italy Abstract
Keywords
Asynclitism is defined as the ‘‘oblique malpresentation of the fetal head in labor’’. Asynclitism is a clinical diagnosis that may be difficult to make; it may be found during vaginal examination. It is significant because it may cause failure of progress operative or cesarean delivery. We reviewed all literature for asynclitism by performing an extensive electronic search of studies from 1959 to 2013. All studies were first reviewed by a single author and discussed with coauthors. The following studies were identified: 8 book chapters, 14 studies on asynclitism alone and 10 papers on both fetal occiput posterior position and asynclitism. The fetal head in a laboring patient may be associated with some degree of asynclitism; this is seen as usual way of the fetal head to adjust to maternal pelvic diameters. However, marked asynclitism is often detected in presence of a co-existing fetal head malposition, especially the transverse and occipital posterior positions. Digital diagnosis of asynclitism is enhanced by intrapartum ultrasound with transabdominal or transperineal approach. The accurate diagnosis of asynclitism, in an objective way, may provide a better assessment of the fetal head position that will help in the correct application of vacuum and forceps, allowing the prevention of unnecessary cesarean deliveries.
Asynclitism, birth canal, cesarean section, delivery, fetal head, malposition, obstructed labor, occiput position, pelvis
Introduction Synclitism of the fetal head is the specific condition in which neither of the parietal bones precedes the sagittal suture into the maternal birth canal. Another definition of synclitism is ‘‘a condition in which the sagittal suture of the fetal head is in line with the transverse diameter of the inlet, equidistant from the maternal symphysis pubis and sacrum’’ [1]. This position is usually detected during vaginal examination, either in late pregnancy or in early labor, when the fetal head enters the pelvic inlet [1]. The absence of synclitism; when one of the parietal bone preceds the sagittal suture is called asynclitism. The one of the earliest documented descriptions of asynclitism, called ‘‘anterior obliquity’’ was presented by Franz Karl Na¨gele in his book published in 1842 [2]. In 1871, Carl Conrad Theodor Litzmann reported the ‘‘posterior
Address for correspondence: Dr. Andrea Tinelli, MD, Department of Gynecology and Obstetrics, Vito Fazzi Hospital, P.zza Muratore, Lecce 73100, Italy. E-mail: [email protected]
History Received 23 June 2014 Revised 1 October 2014 Accepted 1 October 2014 Published online 29 October 2014
obliquity’’ described below as posterior asynclitism [3]. In 1885, Smith described the protuberance of the right parietal bone, after delivery, as ‘‘obliquity of the head’’ [4], while other authors reported asynclitism especially when it was associated with fetal complications [5]. The etymology of asynclitism derives from an ancient Greek word, i.e. Gk, a + syn, not together, kleisis, to lean [6]. In almost any normal labor, the fetal head engages the maternal pelvis with a certain degree of asynclitism. When the anterior parietal bone precedes the sagittal suture, there is an anterior asynclitism (Na¨gele obliquity), whereas if the posterior parietal bone precedes the sagittal suture, there is a posterior asynclitism (Litzmann obliquity) [7,8]. Asynclitism is also defined as the ‘‘oblique malpresentation of the fetal head in labor’’ [9]. Figure 1 shows a vaginal examination in the case of posterior asynclitism in a left occiput transverse position. The first step in the diagnosis of asynclitism is the assessment of the fetal occiput in relationship to the maternal pelvis. Any position of the fetal head, i.e. anterior, transverse and posterior, both left or right, may show a peculiar type of asynclitism (Table 1). In case of anterior
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2
A. Malvasi et al.
Figure 1. Sterile vaginal examination. Fetal head is in left occiput transverse position with posterior asynclitism. The sagittal suture is palpated closer to the symphysis.
Table 1. Different type of asynclitism in each vertex presentation.
J Matern Fetal Neonatal Med, Early Online: 1–5
Asynclitism, especially if marked, is frequently associated with the occiput posterior position [11], but it can be diagnosed in the occiput anterior, right and left, posterior and transverse positions [7]. Asynclitism is usually considered as a physiological part of the birth process, by which the fetal head engages and progresses in the birth canal. When entering the pelvis at the level of the inlet, the fetus is not lying in a perfectly vertical position. Furthermore, a woman’s pelvis is often tilted as well. [9] At the time of a digital examination during labor, identification of the sagittal suture occurs. The sagittal suture will usually be parallel to the largest diameters of the pelvis: the oblique diameter at the inlet and the antero– posterior at the mid and lower pelvis. The next step will be the identification of the anterior or posterior fontanelles, diagnosing the orientation of the occiput in the maternal pelvis, i.e. anterior, posterior, left, right, transverse. Only after the identification of a specific fetal landmark in the maternal pelvis, either the anterior or posterior fontanel, that the correct diagnosis of asynclitism can be made. In cases of minor asynclitism and molding of the fetal head, a safe vaginal delivery, spontaneous or operative, can often be accomplished [11]. However, in the patient with a difficult vaginal examination, as in the presence of excessive molding and caput or occiput posterior and transverse positions, clinical diagnosis may be difficult. Many of these cases are failure to labor progress that need to be resolved with operative vaginal or cesarean delivery [12].
Review of asynclitism literature
asynclitism, the more prominent parietal bone is the one on the opposite side to which the head is rotated towards, whereas in posterior asynclitism the more prominent parietal bone is the one on the same side to which the head is rotated towards. For example, in left occiput position, anterior asynclitism is diagnosed when the right parietal bone is more prominent, whereas posterior asynclitism is diagnosed when the left parietal bone is more prominent. This concept is applicable regardless of the occiput being positioned anteriorly, posteriorly, or transverse.
Asynclitism rates in labor In the literature it is reported that the occiput posterior position is the most common malposition of the fetal head during labor. It occurs in 10–30% of fetuses in the first stage of labor, but most cases resolves spontaneously [10].
Pubmed, Medline, Embase, CINAHL PlusÕ , Web of Science Reference, Scopus, Science Direct and Cochrane Databases online databases were searched, using ‘‘asynclitism’’ as the keyword. Only 14 studies were identified. The word ‘‘asynclitism’’ was reported also in obstetrics books, dictionaries, monographs, and guidelines. The terminology, definitions, and classifications used are the same as those used in the 19th century and early 20th centuries. So, the question that comes spontaneously is why are there so few asynclitism studies in the obstetric literature? There may be various reasons for this. First, there is variability in the definition of asynclitism, its diagnosis and the subsequent obstetric outcomes [13]. A second reason may be that many researchers feel that asynclitism is a normal phenomenon of labor; they consider it to be non-concerning until its degree is so marked that it becomes responsible for a prolonged or obstructed labor. Another possible cause is that with today’s reduction in operative vaginal deliveries, both via forceps or vacuum, and the increase of cesarean deliveries, that this negates the need for an accurate diagnosis of asynclitism. Approximately 5% of all deliveries in the United States are operative vaginal deliveries (1 in 20); the past 20 years have seen a progressive shift away from the use of forceps in favor of the vacuum extractor as the device of choice [14]. The study of Bofil et al. [15] evaluated asynclitism and vaginal operative delivery and concluded that the M-cup
DOI: 10.3109/14767058.2014.972925
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vacuum extractor cup appears to be as efficient (and faster) than forceps, but is associated with significantly more fetal cephalohematomas, whereas maternal injuries are more common when using forceps. Digital vaginal examination has limitations in the diagnosis of asynclitism during the second labor stage. Additionally, at time of delivery, a common sign of asynclitism is a molded or misshapen infant head in parietal zone [8,9]. It has been only since the recent use of ultrasound during labor that new objective signs for the diagnosis of asynclitism have been described [16].
Clinical evaluation: accuracy and limits Sherer [17] demonstrated an overall high rate of error (76%) when fetal head position was assessed in active labor by digital examination compared with diagnosis performed by ultrasound. The jigh rate of error of digital examination persisted (65%) in the second stage of labor, independent of years of clinical experience. (senior residents versus full trained physicians). Uguwumadu et al. [18] reported that in dystocic labor, the presence of the caput succedaneum or scalp hair, especially with associated asynclitism, was responsible for the large error of the digital examination, in a percentage even greater than that reported by Sherer [17,19].
Intrapartum sonography and new diagnosis tools The use of intrapartum ultrasound has been shown to increase the accuracy of detecting abnormal fetal head positions during the second stage of labor [18]. Furthermore, ultrasound has been recently used as a more objective tool in supporting and validating the clinical diagnosis of asynclitism. Different ultrasonographic approaches including transabdominal, transperineal and transvaginal, usually in 2D, have been utilized in the determination of fetal position, using specific fetal landmarks like orbits, cerebellum, midline echo of the brain and
Figure 2. Left occiput posterior position, with anterior asyncitism. Only the anterior orbit is visualized by ultrasound, as the ‘‘squint sign’’ [18] (panel A: graphic representation; panel B: transbdominal ultrasound used up to the beginning of the second stage of labor, with the ‘‘squint sign’’).
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occiput. Ghi et al. [20], have used a 3-D probe for the diagnosis of asynclitism. In making an ultrasonographic diagnosis of asynclitism, Sherer [17] affirmed: ‘‘of note, we find asynclitism may be appreciating subjectively an indirect fashion when difficulty is encountered in depicting symmetrically positioned midline fetal intracranial structure’’. This may lead the operator to use an acute angle of the ultrasound transducer by the operator (in either maternal cephalic or maternal caudal directions) in order to capture the optimal symmetric fetal intracranial image. In the absence of well-depicted maternal structures (symphysis pubis or sacral promontory), the appreciation of asynclitism is very limited. Asynclitism can also be easily diagnosed by ultrasound in occiput posterior position by transabdominal ultrasound. Diagnosis is based on the observation of only a single orbit instead of two, the so-called ‘‘the squint sign’’ (Figures 2 and 3) [9,16]. This sign is confirmed also with translabial sonography in both sagittal and transverse plane, identifying the midline intracranial structures and asymmetry of the cerebellum and the thalamus. An objective diagnosis of asynclitism can also be achieved in case of occiput tranverse position (Figure 4). An early diagnosis of persistent transverse position may allow a more objective management of labor. Uncertainty in clinical assessment of fetal position prior to an operative vaginal delivery, noted in up to 25% of cases, has been objectively improved by the use of intrapartum ultrasound [21]. Our group described two signs for diagnosing asynclitism: the ‘‘squint sign’’ and the ‘‘sunset of thalamus and cerebellum signs’’ [22]. These are two simple ultrasonographic signs allowing detection of anterior and posterior asynclitism. One proposed mechanism for malposition during labor is epidural anesthesia. Labor with low-dose epidural analgesia does not increase the incidence of occipital posterior position, transverse position or asynclitism [23,24]. Transverse fetal head positioning with anterior or posterior asynclitism does
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Figure 3. Right occiput posterior position, with anterior asyncitism (with the ‘‘squint sign’’ in ultrasonographic image).
Figure 4. A left occiput tranverse position (panel A: graphic representation; panel B: transbdominal ultrasound used up to the beginning of the second stage of labor, showing the ‘‘sunset of thalamus and cerebellum signs’’).
not seem to be promoted by drug or technique-related mechanisms, but rather could be the consequence of cephalopelvic disproportion [24,25]. Another way to diagnose asynclitism by ultrasound is with the visualization of the fontanels and sutures. Dikkeboom et al. [26] reported that 3D ultrasound can be a reliable technique for visualizing most fetal cranial sutures and fontanelles. Utilizing sagittal and transverse scans, most of the sutures and fontanels can be visible during the second half of pregnancy. Fuchs et al. [27] showed various images of fetal sutures and fontanelles obtained by 3D ultrasound during labor. The conclusion was that, once the technical difficulties involved in its intrapartum use, 3D ultrasound may be indicated for the determination of the fetal head position in the birth canal in particular for the diagnosis of asynclitism.
Conclusions The presence of asynclitism can frequently be responsible for arrest of labor, and its missed diagnosis may contribute to suboptimal intrapartum management. Even in the presence of
a normal size pelvis [7–9]. Moreover, asynclitism is often associated with other malpositions, especially the transverse and the occipital posterior positions [11,28]. Currently, there are only a few studies on this important clinical entity, indicating a clear need for prospective multicenter randomized trials. Intrapartum sonography has been shown to be of a great help in the diagnosis of asynclitism compared to the more subjective digital examination. Since among the reasons for failure of the vacuum extractor are the occiput posterior position, asynclitism, and uncertain position of the fetal head (a contraindication for operative vaginal delivery) [29], it is important to emphasize that the correct diagnosis of any of these malpositions performed by ultrasound may improve outcomes [21]. The ultrasound diagnosis of occiput posterior position and asynclitism is an objective assessment, and its repercussion is of paramount importance. Increased awareness of the possibility of asynclitism and its correction could significantly decrease the incidence of primary cesarean section [30]. Furthermore, it could be important for correct documentation, for better use of CPT codes and for objective support in cases
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DOI: 10.3109/14767058.2014.972925
with bad outcomes and consequent legal litigation. Diagnosis of asynclitism performed by ultrasound is not meant to replace the digital vaginal exam, but its purpose is to support the diagnosis and improve the management of the second stage of labor. This should encourage physicians to introduce clinical ultrasound examination into their daily practice for the diagnosis and documentation of head malposition and asynclitism [20,22]. Awareness of this very specific obstetric entity is valuable during both the first and the second stage of labor. If diagnosed early, the provider managing labor will be supported in having a more expectant management, whereas if diagnosis is made during the second stage of labor, it will help in making a decision on which route of delivery to choose.
Declaration of interest The authors declare no conflicts of interests. The authors alone are responsible for the content and writing of this article.
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