Wednesday, September 21st, 2016
Purpose of review: To determine the maternal and neonatal outcomes after operative vaginal delivery of foetuses in the persistent occiput posterior position, and examine the efficacy and outcomes of techniques to rotate the foetus into an occiput anterior position prior to vaginal delivery. Summary of findings: A literature search of the MEDLINE/PubMed databases was conducted to identify all study types examining the management of persistent occiput posterior position during labour and subsequent maternal and neonatal outcomes.
Maternal posturing in the last four weeks of pregnancy or during labour has no benefit in reducing the incidence of occiput posterior position at delivery. Rotational operative vaginal deliveries tend to have a low failure rate, however may be associated with anal sphincter injury, despite the overall risk being low. The most current evidence supports the use of rotational forceps in achieving a successful vaginal delivery. Manual rotation followed by direct traction forceps is a commonly performed method of delivery for the occiput posterior positioned foetus, however has only been directly compared to rotational forceps or vacuum in one study, with no demonstrable statistical difference in maternal or neonatal outcomes. Further evidence from the POP-OUT study currently in progress may further support an increasing role for manual rotation in the management of occiput posterior position at delivery.
Occiput posterior (OP) describes the foetal head position where the base of the skull abuts the mother’s sacrum, and the forehead abuts the mother’s symphysis pubis. It is the most common foetal malpresentation and is of clinical important due to its associations with increased maternal and neonatal adverse outcomes. The management of the persistent OP position in labour continues to be an area of debate among obstetricians. Historically there has been conflicting opinion on the morbidity and mortality associated with the OP position. A number of early studies highlighted the increased incidence of operative deliveries and adverse maternal and neonatal outcomes [1, 2]. Interestingly, the basic principles for management of the OP position in labour remain largely unchanged into the modern era of obstetrics – conservative management in the first stage, and conflicting opinions in the second.
Recent studies suggest OP is the most common foetal malpresentation, with reported prevalence of 15-32% at the onset of labour and 5-8% at delivery [3, 4]. Approximately 90% of foetuses in the OP position at the onset of labour rotate into an anterior position without significant prolongation of labour [5]. Therefore the majority of OP positions at delivery arise through failure of rotation to the occiput anterior (OA) position during labour.
Maternal age greater than 35, nulliparity, or gestational age greater than 41 weeks at delivery have a higher incidence of OP position at delivery [4]. Studies have also shown an association between the use of epidural anaesthetic or oxytocin augmentation during labour, and increased rates of OP position at delivery [3]. Although not an established cause, studies have suggested inefficient uterine contractility during labour may account for a proportion of OP positions and may not always be correctible with oxytocin [6].
The OP position is associated with a number of adverse maternal outcomes including increased length of labour, augmentation of labour, chorioamnionitis, anal sphincter injury, and post-partum haemorrhage. Adverse outcomes to the neonate include lower 5-minute Apgar scores, cord blood acidosis, birth trauma, admission to neonatal intensive care units (NICU), and longer duration of stay in hospital [3, 4].
The increased rate of operative deliveries in the persistent OP position is similarly well documented. Studies suggest less than half the number of spontaneous vaginal deliveries occur in OP compared to OA. Furthermore, OP accounts for a disproportionate amount of assisted vaginal deliveries and caesarean sections [6].
Fetal head position has traditionally been determined by digital vaginal examination, by palpating the fontanelles and suture of the foetal skull. However, this has become problematic, as recent evidence suggests that vaginal examination fails to correctly determine the position of the foetal head in 72% of cases in the first stage, and 64% in the second [7]. This finding directly impacts the principles of management, as the exact position of the foetal head should be determined prior to any operative vaginal delivery to ensure safe and correct positioning of the instrument and a successful outcome. Furthermore, this brings into question the reliability of a number of studies in which the diagnosis of OP position was made with digital vaginal examination alone, as there is likely to be a large margin of error. Intrapartum ultrasonography continues to be an operator-dependent method that does not establish the exact position of the foetal head, however a recent study has shown promising results using an algorithm for quantitatively evaluating the position of the foetal head in the maternal pelvis [8]. Advances in ultrasonography techniques will likely continue to improve the utility of this technique, aiding clinicians in deciding whether or not to allow a vaginal delivery. More recent studies, such as the POP-OUT study, are implementing the routine use of transabdominal ultrasound early in the second stage of labour to reliably establish the diagnosis of OP position [9].
A number of large retrospective population based studies have examined the maternal and neonatal outcomes of instrumental vaginal deliveries, however there is limited data comparing the use of forceps and vacuum in the persistent OP position [10]. Furthermore, evidence is lacking for the effectiveness of these techniques in rotating the foetal head to an anterior position to improve outcomes during vaginal delivery.
This review aims to examine the current literature on maternal and neonatal outcomes after instrumental vaginal delivery of foetuses in the persistent OP position, as well as to examine the efficacy and outcomes of techniques to rotate the foetus into the OA position prior to vaginal delivery.
The criteria outlined below were used for consideration of studies to be included in this review.
Types of studies
All published studies of any type including randomised controlled trials, retrospective and prospective cohort studies, retrospective and prospective case-control studies, case series and systematic reviews, examining the management of persistent OP position during labour and subsequent maternal and neonatal outcomes were included.
Types of interventions
The interventions of interest were maternal posturing, operative vaginal delivery including forceps and vacuum, and manual rotation.
Types of outcomes
The primary maternal outcomes to be assessed were the occurrence of anal sphincter injury and postpartum haemorrhage.
The primary neonatal outcomes to be assessed were the occurrence of birth trauma, shoulder dystocia, 5-minute Apgar scores <7, and NICU admission.
For the purposes of this review, only the above short-term outcomes were assessed. However, it should be noted that there are a number of important longer-term outcomes that can be used to assess maternal morbidity. These include bowel and bladder dysfunction and haemorrhoids, which tend to occur more commonly in operative vaginal deliveries, as well as an increased risk of pelvic organ prolapse [11-13]. Recent evidence in this area suggests vacuum extraction shares a comparable risk of pelvic organ prolapse to spontaneous vaginal deliveries, however further discussion is outside the scope of this review [14]. Long-term sequelae of neonatal injury during operative vaginal deliveries appear to be uncommon [15].
Search strategy
An electronic keyword search of the MEDLINE/PubMed databases was conducted to identify studies according to the criteria above. The keywords labor, labour, and occiput posterior were used initially and combined as appropriate with rotation, rotational, operative, instrumental, forceps, vacuum, vaginal delivery using the Boolean operators AND and OR. The reference lists of review articles and other retrieved articles were also searched for relevant studies. The language was restricted to English. All studies up to the 1st of November 2015 were included in the search strategy.
Selection of studies
The author assessed all potential studies identified as a result of the search strategy for inclusion. Only articles with full electronic text available were included in the analysis. To be included in the analysis studies needed to examine at least one maternal or neonatal outcome for an intervention of interest.
A total of 198 studies were identified in the initial electronic search. 123 studies were available with full electronic text in English. 16 studies were screened for inclusion. An additional 8 studies were identified through reference lists and additional electronic searching. 14 studies were included for the final analysis based on the inclusion criteria above (Table 1). Articles were identified for all interventions to be examined. The majority of the included studies were retrospective cohort or population studies.
Table 1: Articles identified from the search strategy
| Author (Year) | Study Design | Intervention(s) | Primary outcomes |
| Damron & Capeless (2004) | ReCS | Forceps
Vacuum |
Anal sphincter injury |
| Demissie et al. (2004) | ReCS | Forceps
Vacuum |
Various maternal and neonatal outcomes |
| Johnson et al. (2004) | ReCS | Forceps
Vacuum |
Various maternal and neonatal outcomes |
| Kariminia et al. (2004) | RCT | Maternal posturing | Incidence of OP at delivery |
| Benavides et al. (2005) | ReCS | Forceps | Anal sphincter injury |
| Wu et al. (2005) | ReCS | Vacuum | Anal sphincter injury |
| Le Ray et al. (2007) | ReCCS | Manual rotation | Manual rotation failure |
| Bahl et al. (2013) | PCS | Manual rotation
Rotational vacuum Rotational forceps |
PPH
Anal sphincter injury Neonatal trauma |
| Desbriere et al. (2013) | RCT | Maternal posturing | Incidence of OP at delivery |
| Stock et al. (2013) | ReCS | Rotational forceps | Various maternal and neonatal outcomes |
| Tempest et al. (2013) | ReCS | Rotational forceps
Rotational vacuum |
Various maternal and neonatal outcomes |
| Phipps et al. (2014) | SR | Prophylactic manual rotation | Various maternal and neonatal outcomes |
| Al Wattar et al. (2015) | SR | Rotational forceps | Various maternal and neonatal outcomes |
| Phipps et al. (2015) | RCT (in progress) | Manual rotation | Various maternal and neonatal outcomes |
RCT – Randomized control trial; ReCS – Retrospective cohort study; PCS – Prospective cohort study; ReCCS – Retrospective case-control study; SR – Systematic review
A number of studies have examined the effect of maternal posturing and pelvic rocking exercises as an intervention for malposition of the foetus, however substantive evidence has been lacking. One study investigated the effect of ten minutes of hands and knees positioning with slow pelvic rocking beginning in the 37th week of gestation and continuing to the time of labour, as a prophylactic intervention to reduce the incidence of foetal malposition [16]. This large, multi-centre randomised controlled trial showed no difference in the incidence of persistent OP position at delivery. In this study foetal position was determined through ultrasonography at the onset of labour. Persistent OP accounted for 32% of all OP neonates at delivery, with the remaining likely to have come about through malrotation, consistent with the literature. This suggests maternal posturing before the start of labour would be of no benefit.
This was further explored in another randomised controlled trial where the intervention group were randomised at the onset of labour after ultrasonography confirmation of the foetal head in the OP position [17]. This study found that intervention with three different maternal postures corresponding to various stages of descent of the foetal head into the maternal pelvis had no significant effect on the foetal head rotation to the anterior position.
Several studies were identified examining maternal and neonatal outcomes in operative vaginal deliveries, however in two of these the data was not separated for OP position and will therefore not be discussed in detail. Briefly, Demissie and colleagues [18] found vacuum deliveries resulted in a lower risk of birth injuries, neonatal seizures, and anal sphincter injury. However in this study, rates of shoulder dystocia and postpartum haemorrhage were higher for vacuum deliveries. This study was limited by the data being sourced from birth certificates and administrative data, however the large sample size provided sufficient power to detect important differences in outcomes. In a smaller retrospective cohort study, the investigators showed vacuum deliveries resulted in less episiotomies (81.8% vs. 90.5%, p = 0.01), and a lower incidence of anal sphincter injury (27.9% vs. 44.4%, p < 0.001) [19]. Interestingly, more periurethral tears were seen in the vacuum-assisted group. Similar Apgar scores and NICU admissions were seen in both groups.
This data suggests vacuum-assistance is superior to forceps in operative vaginal deliveries, however neither of these studies were specific to deliveries in the OP position. A retrospective case study by Damron and Capeless [20] obtained data from 364 operative deliveries in the OP position. The authors found vacuum-assistance had a higher risk of primary instrument failure (33.1% vs. 13.6%, p < 0.0001), but a lower risk of anal sphincter injury (33.1% vs. 71.6%, p < 0.0001). The overall increase in the risk of anal sphincter injury with the use of forceps compared to vacuum has been shown in previous studies [21]. Interestingly this study showed the risk of anal sphincter injury was further increased in the OP position compared to OA (OR 3.25 vs OR 5.25). There was no evaluation of neonatal outcomes measured in this study. The authors’ exclusion of operative rotational procedures limited this study for the purposes of comparing the techniques.
Two further retrospective cohort studies examined the risk of anal sphincter injury in the OP vs. OA position with forceps-assisted or vacuum-assisted vaginal deliveries. Benavides and colleagues [22] showed that anal sphincter injury in forceps-assisted vaginal delivery was significantly more common in the OP position (51.5% vs. 32.9%, p = 0.003). In this study the absolute risk was shown to be lower than previously described [20]. The authors also excluded rotational forceps in the initial analysis, however a subsequent analysis showed that in 39 foetuses rotated from the OP to OA position with forceps, 31% resulted in anal sphincter injury, a rate comparable to the absolute risk for the OA position. A concurrent study examining vacuum-assisted vaginal deliveries also showed anal sphincter injury was more common in the OP position (41.7% vs 22.0%, p = 0.003) [23]. In comparison to the absolute risk shown previously [22], vacuum-assisted vaginal deliveries in the OP position appear to be associated with a reduced risk of anal sphincter injury. None of the above-mentioned studies were designed to show superiority, and further comparative studies would aid clinicians in deciding which instrument to choose.
Survey suggest that rotational forceps (RF) are being much less frequently used when when malposition delays delivery, attributed to a rise in use of rotational vacuum (RV) or caesarean section [24]. In a comparative retrospective study, women were eight times more likely to undergo caesarean section if RV was selected to assist birth rather than RF [25]. The low numbers in the RV group compared to RF in this study (107 vs. 1038) did not allow statistical comparison of maternal outcomes. Of the results obtained however, the absolute incidence of anal sphincter injury with RF remained low (2.4%), and no cases of anal sphincter injury were observed with the use of RV. The incidence of maternal haemorrhage was similar in both groups (1.8% RF vs. 1.9% RV). No significant differences were seen in neonatal outcomes such as lower 5-minute Apgar scores, admission to NICU, or cord blood acidosis, however there was a non-significant increase in shoulder dystocia in RF deliveries (6.2% vs. 3.7%). While this data suggests that RF is associated with the highest chance of achieving a vaginal birth without significant increase in maternal or neonatal morbidity, further studies are required for a definitive conclusion. Furthermore, delivery of the malpositioned foetus was either conducted or directly supervised by experienced obstetrician with at least 6-7 years of specialist training. This may have introduced bias as the skill level of the clinician may have impacted the outcomes of the chosen technique. This is further highlighted by the overall risk of anal sphincter injury being much lower than previous studies [20].
In a similar study, Stock and colleagues [26] also examined the maternal and neonatal outcomes of RF deliveries. This study was primarily designed for descriptive purposes and included a comparison with other types of deliveries in a secondary analysis. Thus, caution should be taken when interpreting this data. The initial analysis of 873 rotational forceps deliveries found a rate of anal sphincter injury of 6.1%. The secondary comparative analysis was limited by the inclusion of only successful RF deliveries in a single year (2008) and the lower number of cases in the RF group (n = 150). No comparison was made to RV, nor did the study include data on patients undergoing manual rotation prior to instrumental delivery. The rate of anal sphincter injury after RF delivery was 9.3% and comparable with non-rotational forceps (8.5%, p = 0.64), but higher than vacuum (1.9%, p = 0.005) or spontaneous delivery (2.9%, p < 0.001). No statistically significant differences in postpartum haemorrhage were observed between RF and non-rotational forceps (5.3% vs. 7.2%, p = 0.49) or ventouse delivery (5.3% vs. 2.5%, p = 0.25), however lower rates were observed for spontaneous delivery (5.3% vs. 2.3%, p = 0.027). It should be noted that the comparison groups are not specific for the OP position. There were no statistical differences in NICU admissions or neonatal encephalopathy between the modes of vaginal delivery. Interestingly, delivery by emergency caesarean showed an increase in NICU admission compared to RF (3.3% vs 11.2%, p = 0.002). Despite the limitations, this study showed RF deliveries overall had a low incidence of neonatal and maternal morbidity.
A recent meta-analysis compared the safety and efficacy of RF and RV [27]. Data was obtained for 5870 rotational vaginal deliveries performed with forceps. Most of this data came from retrospective cohort studies, with only one prospective study included. In direct comparison to RF, RV showed a significantly higher risk of failure in achieving vaginal delivery. There were no significant differences in maternal outcomes such as anal sphincter injury, haemorrhage, or extended tears. Furthermore, there was a significantly lower risk of neonatal trauma with RF, and no significant difference in NICU admission, neonatal jaundice, or shoulder dystocia. This study currently provides the most robust evidence in this area. However, it is important to note that no randomised controlled trials have been performed and the authors state the quality of included studies was generally poor with significant sources of bias such as moderate selection bias and a high risk of comparability and outcome assessment bias.
Manual rotation (MR) of the foetal head from OP to OA position during the second stage of labour is a relatively simple intervention that may increase the chance of normal vaginal delivery. In one study, investigators showed that MR was a successful intervention in 90.3% of cases, with 69.6% successful on the first attempt [28]. Interestingly, none of the fourth or fifth attempts were successful, suggesting that more than three attempts may have no benefit. Rotation failure was more common in nulliparity and a maternal age >35 years. The authors showed the risk of anal sphincter injury was minimal in both successful and unsuccessful rotations, and that although manual rotation may induce foetal heart rate abnormalities, there is no association between foetal heart rate abnormalities after manual rotation and caesarean delivery.
Overall, this study suggests that MR may be an effective technique for reducing the caesarean delivery rate in patients with an OP position during labour. Although this opinion is shared by 97% of obstetricians in Australia and New Zealand, only a minority regularly perform MR [29]. Furthermore, it has been suggested that more obstetricians would be willing to perform the procedure if more robust evidence showed a reduction in the operative delivery rate [29].
Bahl and colleagues [30] conducted a prospective cohort study of 381 nulliparous women who had rotational operative vaginal deliveries, comparing MR with RV and RF. It is important to note that in this study, direct traction forceps followed MR. In this study MR was the most commonly performed method of rotation accounting for 42.8% of deliveries (followed by RF 38.1% and RV 19.1%). There were no significant differences in anal sphincter injury or postpartum haemorrhage between the three interventions. Additionally, there were no significant differences between the groups when comparing neonatal outcomes including 5-minute Apgar scores <7, cord blood acidosis, birth trauma, NICU admissions or shoulder dystocia. Compared with RV, MR was significantly less likely to result in sequential use of instruments (OR 0.01; 95% CI 0.002-0.09 p<0.05). This data showed rotational operative vaginal deliveries including MR, RV and RF had a low failure rate (6.8%) and are associated with few adverse maternal and neonatal outcomes. This study was limited by its cohort design and low number of cases. Additionally, the authors presented no significance levels for their findings.
A recent systematic review investigating the efficacy of prophylactic MR to reduce operative delivery found only one small pilot study, which showed no clear difference in the operative delivery rate [31, 32]. Thus, there remains insufficient evidence to determine the efficacy of MR. However the POP-OUT study, a randomised controlled trial currently in progress, will determine the effect of MR at full dilatation in reducing the operative delivery rate, as well as a number of secondary maternal and neonatal outcomes [9]. The results of this trial may provide the robust evidence needed to inform future practice amongst obstetricians.
Based on the current available evidence, this review has demonstrated the following. Maternal posturing in the last four weeks of pregnancy or during labour has no benefit in reducing the incidence of OP position at or before delivery. Therefore, no posture should be imposed on women with OP position during labour. Rotational operative vaginal deliveries tend to have a low failure rate when performed by experienced clinicians, however may be associated with anal sphincter injury, despite the overall risk being low. Despite current trends favouring the use of rotational vacuum, the most current evidence supports the use of rotational forceps in achieving a successful vaginal delivery with no increase in maternal morbidity, and a lower rate of neonatal trauma. Manual rotation followed by direct traction forceps is a commonly performed method of delivery for the OP positioned foetus, however has only been directly compared to rotational forceps or vacuum in one study, with no demonstrable statistical difference in maternal or neonatal outcomes. At the completion of the POP-OUT study, new evidence may support an increasing role for manual rotation in the management of OP position at delivery.
Acknowledgements
The author would like to acknowledge Associate Professor Andrew Bisits from the Royal Hospital for Women for his mentorship and continuing passion for teaching medical students.
Conflicts of Interest
None declared.
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