The Fetal Occiput Posterior Position: State of the Science and a New Perspective

Abstract: Background: The fetal occiput posterior position poses challenges in every aspect of intrapartum care—prevention, diagnosis, correction, supportive care, labor management, and delivery. Maternal and newborn outcomes are often worse and both physical and psychological traumas are more common than with fetal occiput anterior positions. The purpose of this paper is to describe nine prevailing concepts that guide labor and birth management with an occiput posterior fetus, and summarize evidence to clarify the state of the science. Methods: A search was conducted of the databases of PubMed and the Cochrane Library. Additional valuable information was obtained from obstetric and midwifery textbooks, books and websites for the public, conversations with maternity care professionals, and years of experience as a doula. Results: Nine prevailing concepts are as follows: (1) prenatal maneuvers rotate the occiput posterior fetus to occiput anterior; (2) it is possible to detect the occiput posterior fetus prenatally; (3) a fetus who is occiput anterior at the onset of labor will remain in that position throughout labor; (4) back pain in labor is a reliable sign of an occiput posterior fetus; (5) the occiput posterior fetus can be identified during labor by digital vaginal examination; (6) an ultrasound scan is a reliable way to detect fetal position; (7) maternal positions facilitate rotation of the occiput posterior fetus; (8) epidural analgesia facilitates rotation; (9) manual rotation of the fetal head to occiput anterior improves the rate of occiput anterior deliveries. Concepts 1, 2, 3, 4, 5, and 8 have little scientific support whereas concepts 6, 7, and 9 are supported by promising evidence. Conclusions: Many current obstetric practices with respect to the occiput posterior position are unsatisfactory, resulting in failure to identify and correct the problem and thus contributing to high surgical delivery rates and traumatic births. The use of ultrasound examination to identify fetal position is a method that is far superior to other methods, and has the potential to improve outcomes. Research studies are needed to examine the efficacy of midwifery methods of identification, and the effect of promising methods to rotate the fetus (simple positional methods and digital or manual rotation). Based on the findings of this review, a practical approach to care is suggested. (BIRTH 37:1 March 2010)     

Research on the progress of the fetal head in the occipito-posterior position

We have studied by means of B type ultrasound, the fetal positions and their progress in 221 cases, among which 117 were serially observed. The results showed a marked increase in the incidence of occipito-posterior position (OP) after onset of labor and marked decrease of occipito-anterior position (OA). The antepartum fetal position was influenced mainly by placental site but during labor also by the type and size of the pelvis. The incidence of OP after onset of labor was 33.03% of which 53.13% could rotate spontaneously to anterior position and be delivered as such but 29.69% remained as persistent occipito-posterior position (POP). We also discussed about the differences in the duration and types of deliveries in OP as determined by different labor processes as well as the relationship between the different labor processes and the three major factors affecting labor, particularly in occiput left posterior and occiput right posterior positions.     

Diagnosis and intervention for occiput posterior malposition

OBJECTIVES: To evaluate diagnostic methods used to detect occiput posterior and to describe the efficacy of posturing to enhance rotation from occiput posterior to occiput anterior. DATA SOURCES: Keyword search using PubMed, CINAHL, Cochrane Review, and Dissertation Abstracts International. STUDY SELECTION: Studies published from 1996 to 2006 (except one published in 1983) that focused on the use of ultrasonography versus digital vaginal examination to diagnose fetal position and maternal posturing to enhance rotation from occiput posterior to occiput anterior. DATA EXTRACTION: Eight prospective studies regarding malposition diagnosis were reviewed and analyzed for error rates and predictors affecting ability to detect fetal position; five randomized controlled trials were evaluated for effects of various maternal postures on fetal rotation from occiput posterior to occiput anterior. DATA SYNTHESIS: If fetal malposition is accurately diagnosed in early labor, subsequent nursing management can focus on rotation toward occiput anterior position, leading to a safer delivery for mother and baby. CONCLUSIONS: Antepartum ultrasonography is more accurate than digital vaginal examination in diagnosing fetal malposition; however, its efficacy needs to be further explored using randomized controlled trials and cost-benefit analyses before routine use is recommended. Furthermore, Sims' posture on the same side as the fetal spine is recommended during labor to enhance rotation from occiput posterior to occiput anterior.     

Vaginal versus ultrasound examination of fetal occiput position during the second stage of labor

OBJECTIVE: The purpose of this study was to determine whether ultrasonography is more accurate than vaginal examination in the determination of fetal occiput position in the second stage of labor. STUDY DESIGN: Eighty-eight patients in the second stage of labor were evaluated by vaginal examination and by combined transabdominal and transperineal ultrasound examination to determine occiput position. These predictions of position were compared with the actual delivery position at vaginal delivery after spontaneous restitution or at cesarean delivery. Different examiners performed the vaginal examinations and the ultrasound examinations. Each examiner was blinded to the determination of the other examiner. RESULTS: Vaginal examination determined fetal occiput position correctly 71.6% of the time; ultrasound examination determined fetal occiput position correctly 92.0% of the time (P=.018). CONCLUSION: Ultrasound examination is more accurate than vaginal examination in the diagnosis of fetal occiput position in the second stage of labor.     

Sonographic assessment of fetal occiput position during the second stage of labor: how reliable is the transperineal approach?

Objective: To compare the accuracy of transperineal (TP) ultrasound with transabdominal (TA) approach in the sonographic assessment of fetal occiput position during the second stage of labour.

Methods: A series of low-risk women at term attending the labour ward of three university hospitals were prospectively recruited for the purpose of this study. During the second stage of labor patients were evaluated first by TP and than by TA ultrasound to determine the fetal position. The occiput position was labelled as DOA (direct occiput anterior), ROA (right occiput anterior), LOA (left occiput anterior), DOP (direct occiput posterior), ROP (right occiput posterior), LOP (left occiput posterior), ROT (right occuput transverse) and LOT (left occiput transverse). The agreement between the two techniques was assessed.

Results: Overall 80 patients were recruited in the study group. Ultrasound examination was performed at 21(±8) minutes from the beginning of the active pushing. The ultrasound findings of the fetal occiput position were recorded. In all cases TA ultrasound confirmed the fetal occiput position as determined at TP approach except in one case of ROA that had been recorded as ROT using TP ultrasound.

Conclusions: Ultrasound TP examination is accurate in the diagnosis of fetal occiput position during the second stage of labor.     

Influence of persistent occiput posterior position on delivery outcome.

OBJECTIVE: To evaluate the influence of intrapartum persistent occiput posterior position of the fetal head on delivery outcome and anal sphincter injury, with reference to the association with epidural analgesia. METHODS: We conducted a prospective observational study of 246 women with persistent occiput posterior position in labor during a 2-year period, compared with 13,543 contemporaneous vaginal deliveries with occiput anterior position. RESULTS: The incidence of persistent occiput posterior position was significantly greater among primiparas (2.4%) than multiparas (1.3%; P <.001; 95% confidence interval 1.4, 2.4) and was associated with significantly higher incidences of prolonged pregnancy, induction of labor, oxytocin augmentation of labor, epidural use, and prolonged labor. Only 29% of primiparas and 55% of multiparas with persistent occiput posterior position achieved spontaneous vaginal delivery, and the malposition was associated with 12% of all cesarean deliveries performed because of dystocia. Persistent occiput posterior position was also associated with a sevenfold higher incidence of anal sphincter disruption. Despite a high overall incidence of use of epidural analgesia (47% versus 3%), the institutional incidence of persistent occiput posterior position was lower than that reported 25 years ago. CONCLUSION: Persistent occiput posterior position contributed disproportionately to cesarean and instrumental delivery, with fewer than half of the occiput posterior labors ending in spontaneous delivery and the position accounting for 12% of all cesarean deliveries for dystocia. Persistent occiput posterior position leads to a sevenfold increase in the incidence of anal sphincter injury. Use of epidural analgesia was not related to the malposition.     

The association between persistent occiput posterior position and neonatal outcomes

OBJECTIVE: To examine the effect of persistent occiput posterior position on neonatal outcome. METHODS: This is a retrospective cohort study of 31,392 term, cephalic, singleton births. Women with neonates born in persistent occiput posterior position at delivery were compared to those with occiput anterior position. Women with occiput transverse position were excluded. The association between occiput posterior position and neonatal outcomes, including 5-minute Apgar scores, umbilical cord gases, meconium-stained amniotic fluid, meconium aspiration syndrome, birth trauma, admission to the intensive care nursery, and length of stay were examined using chi(2) and Student t tests. Potential confounders (maternal age, ethnicity, parity, gestational age, epidural anesthesia, labor induction, length of labor, meconium, chorioamnionitis, birth weight, and year of delivery) were controlled for by using multivariable logistic regression and linear regression analyses. RESULTS: There were 2,591 (8.2%) neonates delivered in occiput posterior position of the total cohort of 31,392 deliveries. Compared with occiput anterior, neonates delivered in occiput posterior position had higher risks for adverse outcomes, including 5-minute Apgar score less than 7 (odds ratio [OR] 1.50, 95% confidence interval [CI] 1.17-1.91), acidemic umbilical cord gases (OR 2.05, 95% CI 1.52-2.77), meconium-stained amniotic fluid (OR 1.29, 95% CI 1.17-1.42), birth trauma (OR 1.77, 95% CI 1.22-2.57), admission to the intensive care nursery (OR 1.57, 95% CI 1.28-1.92), and longer neonatal stay in the hospital (OR 2.69, 95% CI 2.22-3.25). CONCLUSION: Persistent occiput posterior position at delivery is associated with higher risks of adverse neonatal outcomes compared with neonates delivered in the occiput anterior position. This information may be important in counseling women who experience persistent occiput posterior position in labor. Level of Evidence: II-2.     

Shock management in acute fetomaternal hemorrhage

Abstract

The determination of fetal head position can be useful in labor to predict the success of labor management, especially in case of malpositions. Malpositions are abnormal positions of the vertex of the fetal head and account for the large part of indication for cesarean sections for dystocic labor. The occiput posterior position occurs in 15–25% of patients before labor at term and, however, most occiput posterior presentations rotate during labor, so that the incidence of occiput posterior at vaginal birth is approximately 5–7%. Persistence of the occiput posterior position is associated with higher rate of interventions and with maternal and neonatal complications and the knowledge of the exact position of the fetal head is of paramount importance prior to any operative vaginal delivery, for both the safe positioning of the instrument that may be used (i.e. forceps versus vacuum) and for its successful outcome. Ultrasound (US) diagnosed occiput posterior position during labor can predict occiput posterior position at birth. By these evidences, the time requested for fetal head descent and the position in the birth canal, had an impact on the diagnosis of labor progression or arrested labor. To try to reduce this pitfalls, authors developed a new algorithm, applied to intrapartum US and based on suitable US pictures, that sets out, in detail, the quantitative evaluation, in degrees, of the occiput posterior position of the fetal head in the pelvis and the birth canal, respectively, in the first and second stage of labor. Authors tested this computer system in a settle of patients in labor.     

Determination of fetal occiput position by ultrasound during the second stage of labor

OBJECTIVE: To investigate whether ultrasonography is superior to vaginal examination for determination of fetal occiput position during the second stage of labor. METHODS: We conducted a prospective cohort study of 44 parturients. During the second stage of labor, an attending obstetrician performed a vaginal examination to detect fetal occiput position. This was followed by combined abdominal and perineal ultrasound examination. The two methods were compared to the true position. Results were analyzed using Student's t test for quantitative parameters. McNemar's and Fisher's exact tests were applied in order to examine differences between the study groups. RESULTS: The error rate in detecting fetal occiput position was significantly lower using the ultrasound technique (6.8%) compared to vaginal examination (29.6%, p = 0.011). Parity, maternal body mass index or fetal weight had no influence on the error rate. CONCLUSIONS: Ultrasonographic determination of the fetal position is an accurate technique and is superior to vaginal examination.     

Determination of fetal occiput position by ultrasound during the second stage of labor

Objective: To investigate whether ultrasonography is superior to vaginal examination for determination of fetal occiput position during the second stage of labor. Methods: We conducted a prospective cohort study of 44 parturients. During the second stage of labor, an attending obstetrician performed a vaginal examination to detect fetal occiput position. This was followed by combined abdominal and perineal ultrasound examination. The two methods were compared to the true position. Results were analyzed using Student's t test for quantitative parameters. McNemar's and Fisher's exact tests were applied in order to examine differences between the study groups. Results: The error rate in detecting fetal occiput position was significantly lower using the ultrasound technique (6.8%) compared to vaginal examination (29.6%, p = 0.011). Parity, maternal body mass index or fetal weight had no influence on the error rate. Conclusions: Ultrasonographic determination of the fetal position is an accurate technique and is superior to vaginal examination.     

持续性枕后位的临床特点及分娩方式选择

目的探讨持续性枕后位的临床特点及分娩方式。方法采用回顾性分析方法，对1998年1月至2004年12月在重庆医科大学两所附属医院住院分娩的112例持续性枕后位（枕后位组）和112例枕前位（枕前位组）的临床资料进行分析，比较两组产程情况、分娩方式及母儿结局。结果两组头位分娩评分、第一产程、第二产程及总产程时间比较，差异有显著性意义（P〈0．05）。枕后位组产钳助产、剖宫产、会阴裂伤、产后出血、胎儿窘迫、新生儿窒息率等均明显高于枕前位组，差异均有显著性意义（P〈0．05）。枕后位组宫口扩张及胎头下降延缓和第二产程延长的发生率均高于枕前位组，差异均有显著性意义（P〈0．05）。剖宫产组富口扩张延缓、胎头下降停滞和第二产程延长的发生率明显高于阴道分娩组（P〈0．05）。而剖宫产组和阴道分娩组骨盆临界狭窄、潜伏期及活跃期延长的发生率比较，差异无显著性意义（P〉0．05）。结论持续性枕后位导致母儿并发症增加，及时处理并选择最佳分娩方式可减少母儿并发症的发生。     

Labor with abnormal presentation and position

Abnormal presentation and position are encountered infrequently during labor. Breech and transverse presentations should be converted to cephalic presentations by external cephalic version or delivered by cesarean section. Face, brow, and compound presentations are usually managed expectantly. Persistent occiput transverse positions are managed by rotation to anterior positions and delivered as such. Occiput posterior positions can be delivered as such or rotated to occiput anterior positions. As with any position or presentation, an obstetrician should not hesitate to abandon any rotational or operative vaginal procedure and proceed to cesarean delivery if rotation or descent does not occur with relative ease.     

持续性枕横位和枕后位病例的产程特点及影响

目的探讨持续性枕横位和枕后位的产程特点及对母儿结局的影响。方法回顾性分析64例持续性枕横位和51例持续性枕后位病例的各阶段产程时间、异常产程及产道损伤、产后出血、羊水粪染(Ⅱ°以上)、新生儿Apgar评分(5min评分≤7分)等情况,并与同期100例枕前位病例进行对比分析。结果持续性枕横位和枕后位的异常产程发生率、产道损伤、产后出血率均较对照组明显增加(P<0.05);羊水粪染及新生儿窒息发生率均较对照组明显增加,两组比较差异均有统计学意义(P<0.05)。结论重视对持续性枕横位和枕后位的早期诊断和及时处理对减少母儿并发症有重要意义。     

Fetal cerebellar measurements in second trimester ultrasonography--clinical value

During routine ultrasound examination of 178 normal pregnant women at 17-24 weeks, several biometric measurements were performed including transverse cerebellar diameter, cavum septum pellucidum, anterior and posterior horns of cerebral ventricles and nuchal soft tissue. The transverse cerebellar diameter is easy to obtain at this gestational age even in occiput posterior position and seems to be independent of head shape and inter-individual constitutional discrepancies. Transverse cerebellar diameter seems to be a good marker for gestational age compared to other clinical and biometric parameters.     

Manual rotation in occiput posterior or transverse positions: risk factors and consequences on the cesarean delivery rate

OBJECTIVE: To identify the risk factors for failure of manual rotation in patients with occiput posterior or transverse positions during labor and to study the cesarean rate according to the success of the rotation. METHODS: Case-control study comparing failure and success of manual rotation. Cases were all fetuses for whom rotation failed. We used computerized randomization (without matching) to select one control with a successful rotation during the same period for each case with a failed rotation. Maternal, neonatal, and obstetric risk factors for failed rotation were studied with bivariable and multivariable analyses. Mode of delivery was analyzed according to success of the rotation. RESULTS: During the study period, manual rotations were performed in 796 patients. The procedure failed in 77 (9.7%) women. Attempted rotation before full dilatation tripled the risk of failure in comparison with rotation at full dilatation (adjusted odds ratio 3.4, 95% confidence interval 1.3-8.6), and rotation for failure to progress quadrupled that risk in comparison with prophylactic rotation (adjusted odds ratio 3.3, 95% confidence interval 1.2-8.5). Failure of manual rotation was associated with a higher cesarean delivery rate than was success (58.8% compared with 3.8%, P<.001). All women with unsuccessful manual rotations who delivered vaginally delivered in the occiput posterior position, and all women with successful manual rotation delivering vaginally delivered in the occiput anterior position. CONCLUSION: Manual rotation may be an effective technique for reducing the cesarean delivery rate in patients with an occiput posterior or transverse position during labor. The success or failure of attempted manual rotation depends upon obstetric conditions, including the indication for rotation and cervical dilatation.     

Impact on delivery outcome of ultrasonographic fetal head position prior to induction of labor

OBJECTIVE: To assess clinical and sonographic fetal head position before induction of labor, position at delivery, and whether occiput posterior (OP) position is associated with adverse delivery outcome. METHODS: Abdominal palpation and ultrasonographic fetal head and spine position were determined at 36 weeks or more of gestation in 289 women immediately before induction of labor and the head position at delivery noted. Chi-square, Mann-Whitney U tests, and logistic regression were used to assess whether OP position was associated with cesarean delivery. RESULTS: Ninety-seven (36%) of 270 women with full outcome data had an OP position on ultrasonography before induction of labor. Of these 97 women, eight (8%) were OP at delivery. Sixty-eight percent of the 25 OP positions at delivery occurred due to a mal-rotation from a non-OP position during labor. Logistic regression showed that OP position before induction of labor was not an independent predictor of cesarean delivery (odds ratio 1.75, 95% confidence interval 0.97-3.15, P=.06). CONCLUSION: Two thirds of OP positions at delivery after induction of labor occur due to a mal-rotation in labor from a non-OP position. Ultrasonography is an easy method of assessing fetal head position before induction of labor. In clinical practice, its usefulness is limited by the fact that, contrary to conventional teaching, OP position before induction of labor does not appear to be associated with an increased risk of cesarean delivery. LEVEL OF EVIDENCE: II.     

Fetal head position during the second stage of labor: comparison of digital vaginal examination and transabdominal ultrasonographic examination

OBJECTIVE: To study the correlation between digital vaginal and transabdominal ultrasonographic examination of the fetal head position during the second stage of labor. METHODS: Patients (n = 110) carrying a singleton fetus in a vertex position were included. Every patient had ruptured membranes and a fully dilated cervix. Transvaginal examination was randomly performed either by a senior resident or an attending consultant. Immediately afterwards, transabdominal ultrasonography was performed by the same sonographer (OD). Both examiners were blind to each other's results. Sample size was determined by power analysis. Confidence intervals around observed rates were compared using chi-square analysis and Cohen's Kappa test. Logistic regression analysis was performed. RESULTS: In 70% of cases, both clinical and ultrasound examinations indicated the same position of the fetal head (95% confidence interval, 66-78). Agreement between the two methods reached 80% (95% CI, 71.3-87) when allowing a difference of up to 45 degrees in the head rotation. Logistic regression analysis revealed that gestational age, parity, birth weight, pelvic station and examiner's experience did not significantly affect the accuracy of the examination. Caput succedaneum tended to diminish (p = 0.09) the accuracy of clinical examination. The type of fetal head position significantly affected the results. Occiput posterior and transverse head locations were associated with a significantly higher rate of clinical error (p = 0.001). CONCLUSION: In 20% of the cases, ultrasonographic and clinical results differed significantly (i.e., >45 degrees). This rate reached 50% for occiput posterior and transverse locations. Transabdominal ultrasonography is a simple, quick and efficient way of increasing the accuracy of the assessment of fetal head position during the second stage of labor.     

Dystocia in late labor: determining fetal position by clinical and ultrasonic techniques

A failure of adequate progression during late labor occurs often and may prohibit an accurate determination of the fetal head position from scalp edema or caput formation. This investigation was undertaken to determine whether ultrasonic evaluation could confirm or correct the digital examination impressions of the fetal head position. Eighty-six attempted vaginal deliveries had recent evidence for arrested cervical dilation after 7 cm or more. An occiput transverse position in 24 (28%) cases was diagnosed accurately, with the need for additional ultrasonic information only in the presence of scalp edema. Distinguishing between a persistent occiput posterior (15 cases, 17%) or anterior (47 cases, 55%) position was often inexact by palpation alone. Combined clinical and ultrasonic impressions allowed for a significantly more precise diagnosis. Ultrasonic imaging allowed for more security while waiting, more confidence with midforceps application, or a prompter decision for cesarean section, depending on the head position.     

Intrapartum sonography for fetal head asynclitism and transverse position: sonographic signs and comparison of diagnostic performance between transvaginal and digital examination

Objective: The primary goal of this study was to determine the ultrasonographic signs of asynclitic and transverse head positioning. In addition, we compared the performance of intrapartum ultrasound to vaginal digital examination. Material & Methods: 150 women were evaluated by 2D transabdominal and translabial ultrasound (US) to detect the asynclitic and deep transverse positions. Transvaginal sterile digital examinations were performed immediately after each intrapartum US assessments, the examinations were repeated at intervals of 45–90 minutes. Examiners were blinded to each other’s findings (clinical or sonographic). Data were reviewed and analyzed by an independent reviewer. Results: The efficacy of digital examination was significantly lower than US evaluation for the detection of either transverse position or asynclitism. The most frequent transverse position was the left one, while the most frequent asynclitism was the anterior one. Conclusions: Digital pelvic examination for detection of fetal head transverse position during labor is inferior to US, especially in the deep transverse positioning, where caput succedaneum occurs and reduces the diagnostic accuracy of vaginal digital examination. The US examination leads to early detection of persistent transverse position allowing for earlier timing and optimal technique for the operative vaginal delivery. We describe two signs for diagnosing asynclitism. The “squint sign” and the “sunset of thalamus and cerebellum signs” are two simple US signs allowing detection of anterior and posterior asynclitism.     

Asynclitism: a literature review of an often forgotten clinical condition

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 co-authors. 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.