Medline ® Abstracts for References 6-14

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 fetuson 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.

OBJECTIVE: To evaluate the obstetric outcomes associated with persistent occiput posterior position of the fetal head in term laboring patients.

METHODS: We performed a cohort study of 6434 consecutive, term, vertex, laboring nulliparous and multiparous patients, comparing those who delivered infants in the occiput posterior position with those who delivered in the occiput anterior position. We examined maternal demographics, labor and delivery characteristics, and maternal and neonatal outcomes.

RESULTS: The prevalence of persistent occiput posterior position at delivery was 5.5% overall, 7.2% in nulliparas, and 4.0% in multiparas (P<.001). Persistent occiput posterior position was associated with shorter maternal stature and prior cesarean delivery. During labor and delivery, the occiput posterior position was associated with prolonged first and second stages of labor, oxytocin augmentation, use of epidural analgesia, chorioamnionitis, assisted vaginal delivery, third and fourth degree perineal lacerations, cesarean delivery, excessive blood loss, and postpartum infection. Newborns had lower 1-minute Apgar scores, but showed no differences in 5-minute Apgar scores, gestational age, or birth weight.

CONCLUSION: Persistent occiput posterior position is associated with a higher rate of complications during labor and delivery. In our population, the chances that a laboring woman with persistent occiput posterior position will have a spontaneous vaginal delivery are only 26% for nulliparas and 57% for multiparas.

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 wellas 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.

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 withmalposition: 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.

The influence of pelvic outlet capacity on fetal head presentation in 1,402 term primiparas with normal pregnancies was studied. In all cases radiological pelvimetry was carried out and labor started spontaneously. Occiput posterior (OP) delivery occurred in 5.1%. As pelvic outlet capacity decreased an increased frequency of OP presentations and need for epidural anesthesia (EDA) was found. With OP presentation the duration of labour was longer, the frequency of EDA, instrumental delivery, cesarean section and low Apgar score at 1 minute were all higher, all compared with occiput anterior (OA) presentation. No difference in fetal morbidity was found. When the influence of the pelvic outlet capacity was eliminated through comparison of matched groups, the course of delivery became more similar whether the presentation was OA or OP and the frequency of EDA became the same. Reduced pelvic outlet capacity seemed to be one cause of both OP presentation and the use of EDA.

OBJECTIVE: To evaluate the effect of fetal position on 1) second-stage labor duration and 2) indicators of maternal and neonatal morbidity.

METHODS: A retrospective cohort study was conducted using a database from a previously reported randomized clinical trial. The data set includes 210 women with the fetus in a posterior position, 200 women with the fetus in a transverse position, and 1,198 women with the fetus in an anterior position. Mean durations of the second stage of labor for different fetal positions were compared using Tukey studentized test. A multivariate logistic regression model was performed to examine the determinants of prolonged second-stage duration (>or= 3 hours). Kaplan-Meier survival curves were used to graph and compare the duration of the second stage of labor for spontaneous delivery according to the fetal position at full dilatation and study group.

RESULTS: Fetal malposition at full dilatation was associated with a significantly increased risk of instrumental vaginal delivery, cesarean delivery, oxytocin administration before full cervical dilatation, episiotomy, severe perineal laceration, and maternal blood loss ofmore than 500 mL (all P values<.01). Compared with the occiput anterior positions, there were significant differences in the duration of the second stage of labor, with a mean of 3.1 hours (95% confidence interval [CI]3.0-3.2) for occiput anterior positions, 3.6 hours (95% CI 3.3-3.9) for occiput transverse positions (P<.05), and 3.8 hours (95% CI 3.5-4.1) for occiput posterior positions (P<.05) in the delayed pushing group. For the early pushing group, means were 2.2 hours (95% CI 2.1-2.3) for occiput anterior positions, 2.5 hours (95% CI 2.3-2.8) for occiput transverse positions (P<.05), and 3.0 hours (95% CI 2.7-3.3) for occiput posterior positions (P<.05).

CONCLUSION: Fetal malposition at full dilatation results in a higher risk of prolonged second stage of labor and increases maternal morbidity indicators.

LEVEL OF EVIDENCE: II-2.

OBJECTIVE: To determine factors associated with term delivery in the occipitoposterior position and examine obstetric outcomes from that delivery position in nulliparas.

METHODS: We did a retrospective analysis of population-based data of 16,781 nulliparas who delivered at term (37-42 weeks) with singleton, cephalic presentations. Factors examined for possible association with occipitoposterior position were fetal weight, maternal age, completed weeks of gestation, epidural analgesia in labor, labor induction, and oxytocin augmentation. Obstetric outcome measures were mode of delivery and percentage of infants with Apgar scores less than 8 at 5 minutes.

RESULTS: The frequency of occipitoposterior position was 4. 6%. Fetal weight, epidural analgesia, and oxytocin augmentation were strongly associated with delivery in the occipitoposterior position (odds ratios 1.18, 2.21, 1.44, respectively, P<.001, logistic regression). There was a higher incidence of instrument and emergency cesarean deliveries in occipitoposterior compared with occipitoanterior labors (43.7% versus 24.4%, 41.7% versus 13.7%, respectively, P<.001, the chi(2) test). There was no significant difference in percentage of infants with low Apgar scores at 5 minutes between those who delivered occipitoposterior or occipitoanterior.

CONCLUSION: Epidural analgesia and oxytocin augmentation are associated with increased incidence of occipitoposterior position, which leads to increased operative obstetric intervention for delivery.

A nine year follow up study of the delivery pattern of 119 women after delivery in the persistent occiput posterior position and their occipito-anterior controls. The studied parameters were: number of deliveries, number of repeated cases of persistent occiput posterior position and operative deliveries. Deliveries in the occipito-posterior position were more common in the study group than in the controls (P= 0.031). Except for this, no statistically significant differences were found between the groups. According to the results, recurrence of the persistent occiput posterior position is common. A history of delivery in the persistent occiput posterior position does not seem to have any major impact on future childbearing.

OBJECTIVE: To determine whether the subpubic arch angle (SPA) measured by three-dimensional ultrasound is associated with the fetal occiput position at delivery and the mode of delivery.

METHODS: Nulliparous women with an uncomplicated singleton pregnancy at ≥ 37 weeks' gestation were recruited from two tertiary centers between September 2013 and August 2015. All women underwent a three-dimensional transperineal ultrasound examination and the SPA was measured using the previously validated Oblique View Extended Imaging software. Data on the outcome of labor were obtained prospectively in all cases and the correlations between SPA and the fetal occiput position at delivery and the incidence of operative delivery were investigated.

RESULTS: Overall, 368 women were included in the study. Fetal position at delivery was occiput anterior in 339 (92.1%) cases and occiput posterior (OP) in 29 (7.9%) cases. A significantly narrower SPA was found in the OP group compared with the occiput anterior group (104.4 ± 16.8°vs 116.4 ± 11.9°; P < 0.0001). The SPA was significantly narrower in women requiring obstetric intervention compared with in women with a spontaneous vaginal delivery. From multivariable logistic regression analysis, SPA and maternal height appeared to be significant predictors of both the fetal occiput position at delivery and the risk of operative delivery. The best cut-off value of SPA for predicting an OP position at delivery was 90.5°.

CONCLUSION: A narrow SPA is associated with a higher risk of persistent OP position at delivery and of operative delivery. Copyright©2015 ISUOG. Published by John Wiley&Sons Ltd.