Occipitoposterior position: associated factors and obstetric outcome in nulliparas

The impact of manual rotation of the occiput posterior position on spontaneous vaginal delivery rate: study protocol for a randomized clinical trial (RMOS)

Background

The frequency of posterior presentations (occiput of the fetus towards the sacrum of the mother) in labor is approximately 20% and, of this, 5% remain posterior until the end of labor. These posterior presentations are associated with higher rates of cesarean section and instrumental delivery. Manual rotation of a posterior position in order to rotate the fetus to an anterior position has been proposed in order to reduce the rate of instrumental fetal delivery. No randomized study has compared the efficacy of this procedure to expectant management. We therefore propose a monocentric, interventional, randomized, prospective study to show the superiority of vaginal delivery rates using the manual rotation of the posterior position at full dilation over expectant management.

Methods

Ultrasound imaging of the presentation will be performed at full dilation on all the singleton pregnancies for which a clinical suspicion of a posterior position was raised at more than 37 weeks’ gestation (WG). In the event of an ultrasound confirming a posterior position, the patient will be randomized into an experimental group (manual rotation) or a control group (expectative management with no rotation). For a power of 90% and the hypothesis that vaginal deliveries will increase by 20%, (10% of patients lost to follow-up) 238 patients will need to be included in the study. The primary endpoint will be the rate of spontaneous vaginal deliveries (expected rate without rotation: 60%). The secondary endpoints will be the rate of fetal extractions (cesarean or instrumental) and the maternal and fetal morbidity and mortality rates. The intent-to-treat study will be conducted over 24 months. Recruitment started in February 2017.

To achieve the primary objective, we will perform a test comparing the number of spontaneous vaginal deliveries in the two groups using Pearson’s chi-squared test (provided that the conditions for using this test are satisfactory in terms of numbers). In the event that this test cannot be performed, we will use Fisher’s exact test.

Discussion

Given that the efficacy of manual rotation has not been proven with a high level of evidence, the practice of this technique is not systematically recommended by scholarly societies and is, therefore, rarely performed by obstetric gynecologists.

If our hypothesis regarding the superiority of manual rotation is confirmed, our study will help change delivery practices in cases of posterior fetal position. An increase in the rates of vaginal delivery will help decrease the short- and long-term rates of morbidity and mortality following cesarean section.

Manual rotation is a simple and effective method with a success rate of almost 90%. Several preliminary studies have shown that manual rotation is associated with reduced rates for fetal extraction and maternal complications: Shaffer has shown that the cesarean section rate is lower in patients for whom a manual rotation is performed successfully (2%) with a 9% rate of cesarean sections when manual rotation is performed versus 41% when it is not performed. Le Ray has shown that manual rotation significantly reduces vaginal delivery rates via fetal extraction (23.2% vs 38.7%, p < 0.01). However, manual rotation is not systematically performed due to the absence of proof of its efficacy in retrospective studies and quasi-experimental before/after studies.

Trial registration

ClinicalTrials.gov, Identifier: NCT03009435. Registered on 30 December 2016

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2497-7) contains supplementary material, which is available to authorized users.

Neonatal outcomes of deliveries in occiput posterior position when delayed pushing is practiced: a cohort study

Background

To examine the impact of occiput posterior position, compared to occiput anterior position, on neonatal outcomes in a setting where delayed pushing is practiced. The specific aim was to estimate the risk of acidaemia.

Methods

Cohort study from a university hospital in Sweden between 2004 and 2012. Information was collected from a local database of 35,546 births. Umbilical artery sampling was routine. Outcomes were: umbilical artery pH < 7.00 and <7.10 and short-term neonatal morbidity. The association between occiput posterior position and neonatal outcomes was examined using logistic regression analysis, presented as adjusted odds ratio (AOR) with 95% confidence interval (CI).

Results

Of 27,648 attempted vaginal births, 1292 (4.7%) had occiput posterior position. Compared with occiput anterior, there was no difference in pH < 7.00 (0.4% vs. 0.5%) but a higher rate of pH < 7.10 in occiput posterior births (3.8 vs. 5.5%). Logistic regression analysis showed no increased risk of pH < 7.10 (AOR 1.28 95% CI 0.93–1.74) when occiput posterior was compared with occiput anterior births but, an increased risk of Apgar score < 7 at 5 min (AOR 1.84, 95% CI 1.11–3.05); neonatal care admission (AOR 1.68, 95% CI 1.17–2.42) and composite morbidity (AOR 1.66, 95% CI 1.19–2.31).

Conclusions

With delayed pushing, birth in occiput posterior compared with anterior position is not associated with acidaemia. The higher risk of neonatal morbidity is of concern and any long-term consequences need to be investigated in future studies.

Epidurals: Do They or Don't They Increase Cesareans?

The controversy over whether epidurals increase the risk of cesarean has raged since the 1970s. This article provides a history of of the early observational research designed to answer this question and an in-depth analysis of the most recent randomized control trials. Based on the research, the author concludes that we cannot assure women that epidurals do not increase the risk of cesarean.

[Labor duration: from normality to dystocia]

"Normal" labor has been surprisingly little studied in the past 60 years even though it is a central axis in obstetrics. Standards were proposed 60 years ago by Emmanuel Friedman and adopted by many countries to become then, driven from Dublin school, the conditions allowing the management of labor: rupture of membranes and oxytocin with, in case of failure for dynamic dystocia, cesarean. Recent data have suggested that labor duration had changed since the 1960s. Changes in women's characteristics and in obstetric practice especially with the widespread use of oxytocin and realization of epidural may have an impact on labor duration. Current studies suggest that it may be possible to authorize longer labor duration without significant increase in maternal or neonatal morbidity. However, it is premature to change practices following the latest American recommendations without prior studies.

Persistent Occiput Posterior position - OUTcomes following manual rotation (POP-OUT): study protocol for a randomised controlled trial

BACKGROUND

Occiput posterior position is the most common malpresentation in labour, contributes to about 18% of emergency caesarean sections and is associated with a high risk of assisted delivery. Caesarean section is now a major contributing factor to maternal mortality and morbidity following childbirth in developed countries. Obstetric intervention by forceps and ventouse delivery is associated with complications to the maternal genital tract and to the neonate, respectively. There is level 2 evidence that prophylactic manual rotation reduces the caesarean section rate and assisted vaginal delivery. But there has been no adequately powered randomised controlled trial. This is a protocol for a double-blinded, multicentre, randomised controlled clinical trial to define whether this intervention decreases the operative delivery (caesarean section, forceps or vacuum delivery) rate.

METHODS/DESIGN

Eligible participants will be (greater than or equal to) 37 weeks' with a singleton pregnancy and a cephalic presentation in the occiput posterior position on transabdominal ultrasound early in the second stage of labour. Based on a background risk of operative delivery of 68%, then for a reduction to 50%, an alpha value of 0.05 and a beta value of 0.2, 254 participants will need to be enrolled. This study has been approved by the Ethics Review Committee (RPAH Zone) of the Sydney Local Health District, Sydney, Australia, and protocol number X110410. Participants with written consent will be randomised to either prophylactic manual rotation or a sham procedure. The primary outcome will be operative delivery (defined as vacuum, forceps and/or caesarean section deliveries). Secondary outcomes will be caesarean section, significant maternal mortality/morbidity and significant perinatal mortality/morbidity. Analysis will be by intention-to-treat. Primary and secondary outcomes will be compared using a chi-squared test. A logistic regression for the primary outcome will be undertaken to account for potential confounders. The results of the trial will be presented at one or more medical conferences. The trial will be submitted to peer review journals for consideration for publication. There will be potential to incorporate the results into professional guidelines for obstetricians and midwives.

TRIAL REGISTRATION

The Australian New Zealand Clinical Trials Registry ACTRN12612001312831 . Trial registered 12 December 2012.

Anterior placental location influences onset and progress of labor and postpartum outcome

INTRODUCTION

The aim of the study is to evaluate whether placental location at term is associated with delivery outcome.

METHODS

A prospective study including 2354 patients with singleton pregnancy at term admitted for vaginal delivery was conducted. Placental position was determined before delivery by ultrasonographic examination performed transabdominally with women in the supine position. Maternal characteristics and delivery outcome such as premature rupture of membranes, induction of labor, mode and gestational age at delivery, indication for cesarean section, duration of the third stage, postpartum hemorrhage (PPH) and manual removal of placenta were correlated with anterior, posterior or fundal placental locations.

RESULTS

Among women enrolled: i) 1164 had an anterior placenta, ii) 1087 a posterior placenta, iii) 103 a fundal placenta. Women with anterior placenta showed: i) a higher incidence of induction of labor (p = 0.0001), especially for postdate pregnancies and prolonged prelabor rupture of membranes (p < 0.0001), ii) a higher rate of cesarean section rate for failure to progress in labor (p = 0.02), iii) a prolonged third stage (p = 0.01), iv) a higher incidence of manual removal of placenta (p = 0.003) and a higher rate of PPH in vaginal deliveries (p = 0.02).

DISCUSSION

The present study showed the influence of anterior placental location on the course of labor, with a later onset of labor, a higher rate of induction and cesarean section and postpartum complications. The reason for this influence on labor and delivery complications remains to be elucidated.

Association between fetal position at onset of labor and mode of delivery: a prospective cohort study

OBJECTIVES

To determine the association between fetal position at onset of labor and mode of delivery, specifically left occipito-anterior (LOA) fetal position and spontaneous vaginal delivery (SVD).

METHODS

All nulliparous women who were booked at the Birmingham Women's NHS Foundation Trust over an 18-month period from April 2007 to September 2008 with a singleton live fetus without structural anomalies at term gestation were invited to take part in the study. Women recruited to the study underwent a transabdominal ultrasound scan to determine fetal occiput position at the onset of labor. They were then followed up until birth to determine outcome. The primary outcome measure was mode of delivery, categorized into SVD, instrumental delivery and Cesarean section.

RESULTS

Of 1647 eligible women, 1250 had valid scans at onset of labor; 155 of the 1250 (12.4%) had fetuses in the LOA position. Analysis showed no evidence of difference in odds ratio (OR) of SVD for fetuses in the LOA position compared with all other positions (OR 0.864 (95% CI, 0.617-1.209); P = 0.394). No difference remained with adjustment for confounding effects of variables known to influence mode of delivery (OR 0.837 (95% CI, 0.551-1.272); P = 0.405). No other occipital position showed significant association with SVD. There was no evidence of the LOA position being associated with Cesarean section, ventouse or forceps delivery.

CONCLUSION

There is no evidence of an association between the fetal LOA position at onset of labor and SVD. This finding challenges the conventional theory that LOA is the optimum fetal position at onset of labor, and suggests that antenatal practices encouraging adoption of the LOA position through maternal posturing are unnecessary.

Maternal experience of musculoskeletal pain during pregnancy and birth outcomes: significance of lower back and pelvic pain

AIM

to examine the association between back and pelvic pain during pregnancy and birth outcomes.

BACKGROUND

back and pelvic pain during pregnancy is a common occurrence. It is known to affect maternal functioning and well-being during pregnancy and can persist postnatally and beyond. However, there has been little examination of the impact upon birth outcomes such as birth mode, duration of labour and pain experience.

METHOD

five hundred and eighty mothers with an infant aged zero to six months completed a retrospective questionnaire documenting their pain during pregnancy and birth outcomes (e.g. mode, duration, interventions, perception of pain). Participants also rated overall pain and pain in specific body regions for each of the three trimesters. Estimations of fetal position before birth were given.

FINDINGS

higher pain ratings during the third trimester of pregnancy were associated with increased incidence of caesarean section, assisted delivery and a longer duration of labour. Specifically, lower back and pelvic pain were associated with an increase in complications, potentially due to occurrence of malpositioning of the fetus during pregnancy.

CONCLUSION

mothers who experience high levels of pain during pregnancy may be at increased risk of complications during labour. Explanations for this may be physiological, mechanical or psychological but greater awareness should be given to the potential impact of maternal pain ratings during pregnancy upon birth outcomes.

Is maternal posturing during labor efficient in preventing persistent occiput posterior position? A randomized controlled trial

OBJECTIVE

We sought to evaluate the efficacy of maternal posturing during labor on the prevention of persistent occiput posterior (OP) position.

STUDY DESIGN

We conducted a randomized trial including 220 patients in labor with a single fetus in documented OP position. Main outcome was the proportion of anterior rotation from OP position.

RESULTS

The rates of anterior rotation were, respectively, 78.2% and 76.4% in the intervention group and the control group without significant difference (P = .748). Rates of instrumental and cesarean section deliveries were not significantly different between intervention and control groups (18.2% vs. 19.1%, P = .89, and 19.1% vs. 17.3%, P = .73, respectively). In intervention and control groups, persistent OP position rates were significantly higher among women who had cesarean section (71.4% and 89.5%, respectively) and an instrumental delivery (25% and 33.3%, respectively) than among women who achieved spontaneous vaginal birth (5.8% and 2.8%, respectively). In multivariable analysis, body mass index and parity were found to have significant and independent impact on the probability of fetal head rotation.

CONCLUSION

Our study failed to demonstrate any maternal or neonatal benefit to a policy of maternal posturing for the management of OP position during labor.

The association between persistent fetal occiput posterior position and perinatal outcomes: an example of propensity score and covariate distance matching

In a retrospective cohort study of 18,880 full-term, cephalic singletons born in San Francisco, California, during 1976-2001, the authors used multivariable logistic regression (MVLR) and propensity score analysis (PSA) to examine the association between persistent fetal occiput posterior (OP) position and perinatal outcomes. The principles and applications of these techniques are compared and discussed. Pregnancies with OP positions at delivery were compared with those with occiput anterior positions. Perinatal outcomes were examined as adjusted odds ratios determined by MVLR and PSA and as risk differences determined by propensity score matched bootstrapping based on covariate distance. Persistent OP position was associated with operative delivery and maternal morbidity. The odds ratio estimates based on PSA were somewhat larger than those obtained with standard MVLR, and the confidence intervals were narrower. When statistical inference was evaluated with the permutation test, the results were more consistent with the PSA. These analyses demonstrate that PSA is likely to provide more precise estimates of exposure associations and more reliable statistical inferences than MVLR. The authors show that PSA can be extended with Mahalanobis distance matching to obtain estimates of risk difference between exposed and unexposed subjects that avoid violations of the experimental treatment assignment (positivity) assumption that is required for valid causal inference.

Associated factors and outcomes of persistent occiput posterior position: A retrospective cohort study from 1976 to 2001

OBJECTIVE

To identify maternal and fetal risk factors associated with persistent occiput posterior position at delivery, and to examine the association of occiput posterior position with subsequent obstetric outcomes.

METHODS

This is a retrospective cohort study of 30 839 term, cephalic, singleton births. Women with persistent occiput posterior (OP) position at delivery were compared to those with occiput anterior (OA) position. Demographics, obstetric history, and labor management were evaluated and subsequent obstetric outcomes examined. Potential confounding variables were controlled for using multivariate logistic regression analysis.

RESULTS

The overall frequency of OP position was 8.3% in the study population. When compared to Caucasians, a higher rate of OP was observed among African-Americans (OR = 1.4, 95% CI 1.25-1.64) while no other racial/ethnic differences were noted. Other associated factors included nulliparity, maternal age > or =35, gestational age > or =41 weeks, and birth weight >4000 g, as well as artificial rupture of the membranes (AROM) and epidural anesthesia (p < 0.001 for all). Persistent OP was associated with increased rates of operative vaginal (OR = 4.14, 95% CI 3.57-4.81) and cesarean deliveries (OR = 13.45, 95% CI 11.94-15.15) and other peripartum complications including third or fourth degree perineal lacerations (OR = 2.38, 95% CI 2.03-2.79), and chorioamnionitis (OR = 2.10, 95% CI 1.81-2.44).

CONCLUSION

Epidural use, AROM, African-American ethnicity, nulliparity, and birth weight >4000 g are associated with persistent OP position at delivery, with higher rates of operative deliveries and obstetric complications. This information can be useful in counseling patients regarding risks and associated outcomes of persistent OP position.

[Instrumental extractions using Thierry's spatulas: evaluation of the risk of perineal laceration according to occiput position in operative deliveries]

OBJECTIVE

Risk factors for severe perineal lacerations are nowadays well-known and they include operative vaginal deliveries and extractions in occiput posterior (OP) positions. The aim of this study was to assess whether OP position increases the risk for anal sphincter injury when compared with occiput anterior (OA) positions in operative deliveries using Thierry's spatulas.

METHODS

Retrospective study of 163 extractions with Thierry's spatulas over a five-year period (January 2000 to December 2005) performed in a general hospital. Singleton cephalic pregnancies at term were studied and the incidence of severe perineal lacerations was noted in deliveries in OP and OA positions.

RESULTS

In these 163 cases, the varieties of presentation obtained by vaginal examination were 129 in anterior and 34 in posterior positions. Eleven posterior positions rotated anteriorly on delivery and 23 remained in a posterior position. The OA group (n=140) and the OP group (n=23) were constituted. Anal sphincter injury occurred significantly more often in the OP group compared with the OA group (17.4% versus 2.9%, p=0.014) with an odds ratio of 7.1 (95% CI 1.6-31). Only one fourth-degree laceration was noted. Within the OP group, the incidence of vaginal lacerations was increased compared to the OA group, but without any significant difference (43.5% versus 27.9%, p=0.20). In a logistic regression model, the OP position was 6.4 times (95% CI 1.3-31.5) more likely to be associated with anal sphincter injury than OA position. The incidence of OP position was 14.1% within the whole population studied and Thierry's spatulas permit anterior rotations of occipito posterior presentation in only 32.4% of cases.

CONCLUSION

The efficiency of Thierry's spatulas is proven. As with forceps and vacuum extractors, extraction with Thierry's spatulas is a risk factor for perineal laceration compared to a spontaneous delivery. In deliveries with spatulas, OP head positions further increase this perineal risk against OA positions. OP positions before fetal extractions do not seem to be an ideal situation for using spatulas, even if an anterior rotation is achieved in one-third of cases.

Diagnostic clinico-échographique et devenir des variétés postérieures dans la présentation du sommet : étude prospective longitudinale de 350 parturientes

OBJECTIVE

To evaluate clinical reliability compared to intrapartum ultrasound as a tool to diagnose occiput posterior position and to investigate the proportion of rotations occurring during labour.

PATIENTS AND METHODS

350 women in labor with a singleton fetus in a vertex position were prospectively studied using ultrasound and obstetrical examination. Outcome of labor was also monitored.

RESULTS

Reliability of clinical examination is 85,7%, initial occiput posterior position represented 40,2% and most rotated in an anterior position (84, 8%) while only 0,6% of initial anterior positions delivered in occiput posterior position. Logistic regression did not allow to find significant predictor of occiput posterior position rotation.

DISCUSSION AND CONCLUSION

Clinical examination is relatively reliable for posterior position diagnosis and in most cases, initially occipitoposterior positions rotate anteriorly.

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.

Is epidural analgesia a risk factor for occiput posterior or transverse positions during labour?

OBJECTIVE

The aim of this study was to assess whether the station of the fetal head at epidural placement is associated with the risk of malposition during labour.

STUDY DESIGN

Retrospective study (covering a 3-month period) of patients in labour with singleton cephalic term fetuses and epidural placement before 5 cm of dilatation. We studied the following risk factors for malposition: station and cervical dilatation at epidural placement, induction of labour, parity and macrosomia. Malposition, defined as all occiput posterior and occiput transverse positions, was assessed at 5 cm of dilatation because of our policy of systematic manual rotation for malpositions.

RESULTS

The study included 398 patients, 200 of whom had malpositions diagnosed at 5 cm of dilatation. In both the univariate and multivariate analyses, station at epidural placement was the only risk factor significantly associated with this malposition (adjusted OR: 2.49, 95% CI 1.47-4.24). None of the other factors studied was significantly associated with malposition: nulliparity (OR 1.45, 95% CI 0.96-2.20), macrosomia (OR 0.75, 95% CI 0.37-1.50), induction of labour (OR 0.84, 95% CI 0.49-1.45), or dilatation less than 3 cm at epidural administration (OR 1.16, 95% CI 0.59-2.30). Only three infants of the 365 delivered vaginally (0.8%) were born in occiput posterior positions.

CONCLUSION

Epidural placement when the fetal head is still "high" is associated with an increased rate of occiput posterior and transverse malpositions during labour.

Occiput posterior fetal head position increases the risk of anal sphincter injury in vacuum-assisted deliveries

OBJECTIVE

The purpose of this study was to determine whether an occiput posterior (OP) fetal head position increases the risk for anal sphincter injury when compared with an occiput anterior (OA) position in vacuum-assisted deliveries.

STUDY DESIGN

We conducted a retrospective cohort study of 393 vacuum-assisted singleton vaginal deliveries. Maternal demographics and obstetric and neonatal data were collected from an obstetric database and chart review.

RESULTS

Within the OP group, 41.7% developed a third- or fourth-degree laceration compared with 22.0% in the OA group (OR 2.5, 95% CI 1.4-4.7). In a logistic regression model that controlled for BMI, race, nulliparity, length of second stage, episiotomy, birth weight, head circumference, and fetal head position, OP position was 4.0 times (95% CI 1.7-9.6) more likely to be associated with an anal sphincter injury than OA position.

CONCLUSION

Among vacuum deliveries, an OP head position confers an incrementally increased risk for anal sphincter injury over an OA position.

The impact of occiput posterior fetal head position on the risk of anal sphincter injury in forceps-assisted vaginal deliveries

OBJECTIVE

A forceps-assisted vaginal delivery is a well-recognized risk factor for anal sphincter injury. Some studies have shown that occiput posterior (OP) fetal head position is also associated with an increased risk for third- or fourth-degree lacerations. The objective of this study was to assess whether OP position confers an incrementally increased risk for anal sphincter injury above that present with forceps deliveries.

STUDY DESIGN

This was a retrospective cohort study of 588 singleton, cephalic, forceps-assisted vaginal deliveries performed at our institution between January 1996 and October 2003. Maternal demographics, labor and delivery characteristics, and neonatal factors were examined. Statistical analysis consisted of univariate statistics, Student t test, chi2, and logistic regression.

RESULTS

The prevalence of occiput anterior (OA) and OP positions was 88.4% and 11.6%, respectively. The groups were similar in age, marital status, body mass index, use of epidural, frequency of inductions, episiotomies, and shoulder dystocias. The OA group had a higher frequency of rotational forceps (16.2% vs 5.9%, P = .03), greater birth weights (3304 +/- 526 g vs 3092 +/- 777 g, P = .004), and a larger percentage of white women (48.8% vs 34.3%, P = .04). Overall, 35% of forceps deliveries resulted in a third- or fourth-degree laceration. Anal sphincter injury occurred significantly more often in the OP group compared with the OA group (51.5% vs 32.9%, P = .003), giving an odds ratio of 2.2 (CI: 1.3-3.6). In a logistic regression model that controlled for occiput posterior position, maternal body mass index, race, length of second stage, episiotomy, birth weight, and rotational forceps, OP head position was 3.1 (CI: 1.6-6.2) times more likely to be associated with anal sphincter injury than OA head position.

CONCLUSION

Forceps-assisted vaginal deliveries have been associated with a greater risk for anal sphincter injury. Within this population of forceps deliveries, an OP position further increases the risk of third- or fourth-degree lacerations when compared with an OA position.

Changes in Fetal Position During Labor and Their Association With Epidural Analgesia

OBJECTIVE

To evaluate whether epidural analgesia is associated with a higher rate of abnormal fetal head position at delivery.

METHODS

We conducted a prospective cohort study of 1,562 women to evaluate changes in fetal position during labor by using serial ultrasound examinations. Ultrasound examinations were performed at enrollment, epidural administration, 4 hours after the initial ultrasonography if epidural had not been administered, and late in labor (> 8 cm). Information about fetal head position at delivery was obtained from the provider.

RESULTS

Regardless of fetal head position at enrollment (occiput transverse, occiput posterior, or occiput anterior), most fetuses were occiput anterior at delivery (enrollment position: occiput transverse 78%, occiput posterior 80%, occiput anterior 83%, P = .1). Final fetal position was established close to delivery. Of fetuses that were occiput posterior late in labor, only 20.7% were occiput posterior at delivery. Changes in fetal head position were common, and 36% of women had an occiput posterior fetus on at least one ultrasound examination. Women receiving epidural did not have more occiput posterior fetuses at the enrollment (23.4% epidural versus 26.0 no epidural, P = .9) or the epidural/4-hour ultrasound examination (24.9% epidural, 28.3% no epidural), but did have more occiput posterior fetuses at delivery (12.9% epidural versus 3.3% no epidural, P = .002); the association remained in a multivariate model (adjusted odds ratio 4.0, 95% confidence interval 1.4-11.1).

CONCLUSION

Fetal position changes are common during labor, with the final fetal position established close to delivery. Our demonstration of a strong association of epidural with fetal occiput posterior position at delivery represents a mechanism that may contribute to the lower rate of spontaneous vaginal delivery consistently observed with epidural.

Ultrasonographic occiput position in early labour in the prediction of caesarean section

OBJECTIVE

To investigate the value of ultrasonographically determined occiput position in the early stages of the active phase of labour, in addition to traditional maternal, fetal and labour-related characteristics, in the prediction of the likelihood of caesarean section.

DESIGN

Prospective observational study.

SETTING

District general hospital in the UK.

POPULATION

Six hundred and one singleton pregnancies with cephalic presentation in active labour at term with cervical dilatation of 3-5 cm.

METHODS

Transabdominal sonography to determine fetal occiput position was carried out by an appropriately trained sonographer immediately before or after the routine clinical examination by the attending midwife or obstetrician.

MAIN OUTCOME MEASURE

Caesarean section.

RESULTS

Delivery was vaginal in 514 (86%) cases and by caesarean section in 87 (14%). The fetal occiput position was posterior in 209 (35%) cases and in this group the incidence of caesarean section was 19% (40 cases), compared with 11% (47 of 392) in the non-occiput posterior group. Multiple regression analysis revealed that significant independent contribution in the prediction of caesarean section was provided by maternal age (OR 1.1, 95% CI 1.0-1.2), Afro-Caribbean origin (OR 2.4, 95% CI 1.2-4.6), height (OR 0.93, 95% CI 0.89-0.97), parity (OR 0.2, 95% CI 0.1-0.4), type of labour (OR 2.2, 95% CI 1.3-3.8), gestation (OR 1.4, 95% CI 1.1-1.7), fetal head descent (OR 0.6, 95% CI 0.4-0.9), occiput posterior position (OR 2.2, 95% CI 1.3-3.7) and male gender (OR 2.0, 95% CI 1.2-3.5).

CONCLUSIONS

The risk of caesarean section can be estimated during the early stage of active labour by the sonographically determined occiput position, in addition to traditional maternal, fetal and labour-related characteristics.

Intrapartum sonography to determine fetal head position

OBJECTIVE

To investigate the accuracy of intrapartum transvaginal digital examination in defining the position of the fetal head.

PATIENTS AND METHODS

In 496 singleton pregnancies in labor at term, the fetal head position was determined by routine transvaginal digital examination by the attending midwife or obstetrician. Immediately before or after the clinical examination, the fetal head position was determined using transabdominal ultrasound by an appropriately trained sonographer who was not aware of the clinical findings. The digital examination was considered to be correct if the fetal head position was within 45 degrees of the ultrasound finding. The accuracy of the digital examination was examined in relation to maternal characteristics and the progress of labor.

RESULTS

The position of the fetal head was determined by ultrasound examination in all 496 cases examined. Digital examination failed to define the fetal head position in 166 (33.5%) cases and, in 330 cases where the position was determined, the findings of the digital and sonographic examinations were in agreement in only 163 (49.4%) cases. The rate of correct identification of the fetal position by digital examination increased with cervical dilatation, from 20.5% at 3-4 cm to 44.2% at 8-10 cm, and was higher if the examination was carried out by an obstetrician than a midwife (50% versus 30%) and if there was absence rather than presence of caput (33% versus 25%).

CONCLUSIONS

Routine digital examination during labor fails to identify the correct fetal position in the majority of cases.

Epidural and spinal analgesia and labour

Epidural and spinal analgesia for pain relief in labour are now commonplace. Adverse effects such as hypotension and toxicity to anaesthetic agents are well described and easily managed. The effects on obstetric outcome, however, have been unclear to both obstetricians and anaesthetists, but are important due to the large number of pregnancies involved. Efforts to define implications for mother and child have been frustrated by a relative lack of evidence derived from good quality, large randomized trials. Ethical and methodological difficulties together with an abundance of confounding factors have conspired to cause considerable difficulties for researchers in this area. Nevertheless, recent evidence has significantly advanced knowledge in the field and has implications for future practice.