Obstetrics & Gynecology:
Effect of Fetal Position on Second-Stage Duration and Labor Outcome
Senécal, Julie MSc*†; Xiong, Xu MD, DrPH†‡; Fraser, William D. MD, MSc†; for the PEOPLE (Pushing Early Or Pushing Late with Epidural) Study Group
From the *Department of Obstetrics and Gynaecology, Laval University; †Department of Obstetrics and Gynaecology, University of Montreal, Montreal, Quebec, Canada; and ‡Department of Epidemiology, Tulane University, New Orleans, Louisiana.
*For a list of other members of the PEOPLE Study Group, see the Appendix.
This study was sponsored by the CIHR (grant MT-12423). AstraZeneca R&D Montreal (Montreal, Quebec, Canada) provided medication.
Reprints are not available. Address correspondence to: William Fraser, Hôpital Sainte-Justine, Centre de Recherche, 3175 Côte Suite Catherine, Room 4986B, Montreal, Quebec, H3S 1S5; e-mail: email@example.com.
Received August 31, 2004. Received in revised form November 20, 2004. Accepted December 2, 2004.
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 (≥ 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 of more 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
Since Mauriceau's classical work was published in 1681,1 the occiput posterior and transverse malpositions have remained an obstetric challenge. Controversy concerning their management persists to the present day.2 Occiput posterior and occiput transverse positions during labor represent the most common cephalic malpositions.1–3 The incidence of occiput posterior position in the first stage of labor has been reported to vary between 6% and 41% (Bernstein PC, Choi Y. Does malposition of the fetus in labor predispose to occiput posterior position at delivery? Am J Obstet Gynecol 1999;184:S122),3–6 whereas the incidence of occiput transverse position in the first stage of labor varies between 33% and 44.5% (Bernstein PC, Choi Y. Am J Obstet Gynecol 1999).6 Standard textbooks state that about 90% of malpositions diagnosed early in labor rotate into an occiput anterior position before delivery.5 The incidence of occiput posterior and occiput transverse positions that persist in the second stage of labor has been reported to be between 4% and 10%.2 Fetal position is frequently first assessed at full dilatation. Few studies have assessed the effects of malposition at full dilatation on second-stage progress or on maternal and neonatal morbidity. Most published studies lack comparison groups.2,10–13 Persistent occiput posterior and occiput transverse positions are associated with prolonged second stages of labor, higher rates of episiotomy, and severe perineal lacerations, mainly owing to higher rates of instrumental delivery.7 As obstetric practice has changed in recent years, it is difficult to know if data from studies performed in the 1970s can be generalized to the modern obstetric practice.
Epidural analgesia is the most frequently used pharmacologic method of pain relief for women during labor.14,15 In the early 1980s, the rate of epidural administration for labor pain relief was 4%.16 In the 1990s, 50–80% of laboring women in North American hospitals received epidural (Statistiques périnatales concernant le pourcentage des femmes ayant eu une analgésie et/ou anesthésie pendant leur travail. Hôpital St-François d'Assise, 2002).17 Epidural analgesia can increase the risk of instrumental vaginal delivery14 and possibly cesarean delivery.18–21 It also influences labor length, particularly the duration of the second stage. Epidural analgesia has been proposed as a risk factor for fetal malposition, in particular when placement of the epidural catheter occurs before the engagement of the fetal head.11,21,22 It has been proposed that relaxation of the pelvic floor after epidural analgesia reduces the likelihood of correct positioning of the fetal head. Consequently, prolonged labor, instrumental delivery, cesarean delivery, and significant perineal trauma are known to be more frequent with persistent malpositions.23
The objectives of this study were to assess the effect of fetal malposition at full dilatation 1) on second-stage labor progress among nulliparous women with epidural analgesia, and 2) on indicators of maternal and neonatal morbidity among nulliparous women with epidural analgesia.
MATERIALS AND METHODS
This is a secondary analysis of a database derived from a previously reported randomized clinical trial of delayed compared with early pushing.24 The trial was performed in 12 hospitals, 11 in North America and 1 in Switzerland, between October 1994 and August 1996. All collaborating hospital centers received the approval of their respective ethics review board for the trial. The inclusion criteria for the study were nulliparity, age 18 years or older, gestational age 37 weeks or more, single fetus in cephalic presentation, normal fetal heart rate pattern status, effective epidural analgesia (pain < 3 on a 10-point visual analogue scale) using a standardized continuous infusion technique (bupivacaine 0.125% and 2 μg/mL fentanyl at a rate of 7–12 mL/h), and full dilatation. Women were excluded from the study in the presence of complicated hypertension, recent hemorrhage, eclampsia, preeclampsia, suspicion of fetal malformation or intrauterine growth restriction, fever of more than 38°C, or the presence of a spontaneous urge to push at the time of full dilatation. At the time of randomization (full dilatation), women were allocated to a policy of delayed pushing or to early pushing. Women in the delayed pushing group were encouraged to avoid expulsive efforts for a period of approximately 2 hours. Women in the early pushing group were encouraged to commence pushing immediately after randomization. Of a total of 1,862 participants in this clinical trial, the position of the fetal head at full cervical dilatation was documented in 1,608 patients. 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. Fetal head position at full dilatation was missing for 254 women. Position of the fetal head at full dilatation was documented by the labor room staff at the time of randomization and documented in the case report form. For the purpose of the analysis, fetal position at full dilatation was categorized into 3 groups: occiput posterior positions, including right occiput posterior, left occiput posterior, or direct occiput posterior positions; occiput transverse positions, including right occiput transverse or left occiput transverse; and occiput anterior positions, including right occiput anterior, left occiput anterior, and occiput anterior positions. The time of full dilatation was carefully documented for all patients.
Indicators of maternal morbidity include cesarean delivery, episiotomy, third- or fourth-degree perineal tear, estimated blood loss of more than 500 mL, and postpartum fever. Indicators of infant morbidity include abnormal arterial cord pH (< 7.10), neonatal intensive care unit admission, neonatal trauma (including cephalohematoma, skull fractures, intracerebral or subdural hematoma, other trauma), and Apgar score < 8 at 5 minutes.
Low- and midforceps and vacuum were defined according to the definition adopted from the Maternal Fetal Medicine Committee of the American College of Obstetricians and Gynecologists (ACOG). This definition has been validated as the method of classification of forceps that best reflects the risk of maternal and neonatal trauma associated with the different procedures.25
Mean values for anthropometric, social, and obstetric characteristics were calculated, as were incidences of fetal and maternal morbidity, according to fetal position at full dilatation. General association Pearson χ2 tests were performed for categorical variables. Mean of continuous variables and of durations of the second stage of labor for fetal position at full dilatation were compared using the Tukey studentized test. The t test was used to compare, within each head-position group, mean durations of the second stage of labor of delay and early pushing groups. A multivariate logistic regression model was performed to examine the determinants of a prolonged second stage of labor of more than 3 hours. To assess the effect of fetal position at full dilatation, we adjusted for station of the fetal head at the beginning of the second stage of labor, maternal age, maternal height, baby birth weight, second-stage oxytocin administration, treatment group, and duration of the first stage of labor. Kaplan-Meier survival curves were used to graph the duration of the second stage of labor for spontaneous vaginal deliveries according to fetal position at full dilatation. The event of origin is full dilatation (time = 0). The end point (time = ∞) is spontaneous vaginal delivery. Censored data included cesarean and operative vaginal deliveries. Statistical analysis was performed using SAS 8.0 (SAS Institute, Cary, NC).
Table 1 shows anthropometric, social, and obstetric characteristics of the study population, according to fetal position at full dilatation. There were no statistically significant differences in maternal height, education, weight gain during pregnancy, gestational age, and newborn birth weight, nor were there differences in the duration of the first stage of labor. Women with babies in the occiput transverse position tended to be older than those with babies in the occiput anterior and occiput posterior positions, and women for whom the fetal position at full dilatation was not documented tended to be younger: 27.7 years for occiput anterior (95% confidence interval [CI] 7.3–27.9), 28.6 years for occiput transverse (95% CI 28.0–29.3; P < .05), 27.7 years for occiput posterior (95% CI: 27.0–28.3), and 26.6 years for the missing data group (95% CI 26.0–27.3; P < .05). Women who were of origin other than white or Asian were more frequently represented in the category of patients where fetal position at full dilatation was not documented (5% in occiput anterior, 3.5% in occiput transverse, 5.2% in occiput posterior, and 12.6% in the missing data group). Assignment of treatment group (early compared with delayed pushing) was significantly different between fetal position groups (P < .001). High fetal station at full dilatation was more frequent when the baby was in the occiput posterior position or in the missing position group compared with the occiput anterior position. Table 2 shows obstetric and neonatal outcomes according to fetal position at full dilatation. Occiput posterior and occiput transverse positions were associated with a significantly increased risk of maternal morbidity, including higher rates of episiotomy (47.4% for occiput posterior, 46.5% for occiput transverse, and 38.6% for occiput anterior), estimated blood loss of more than 500 mL (26.7% for occiput posterior, 19.5% for occiput transverse, and 15.8% for occiput anterior), cesarean delivery (15.2% for occiput posterior, 6.0% for occiput transverse, and 3.4% for occiput anterior), and third- or fourth-degree perineal tear (10.0% for occiput posterior, 13.0% for occiput transverse, and 8.0% for occiput anterior). The incidence of mid-vaginal and low-assisted procedures with rotation was higher in occiput posterior and occiput transverse groups than in the occiput anterior groups, with the exception of low procedures, which had a higher incidence in the occiput anterior position; more specifically, mid-procedures (24.0% for occiput posterior, 16.0% for occiput transverse, and 8.6% for occiput anterior), low procedures with rotation (5.3% for occiput posterior, 8.0% for occiput transverse, and 1.4% for occiput anterior), and low procedures without rotation (21.5% for occiput posterior, 21.0% for occiput transverse, and 26.5% for occiput anterior). There was no difference in the distribution of indicators of neonatal morbidity according to the fetal position. However, neonatal trauma (cephalohematoma, fracture, hematoma, cranial fracture, and other trauma) was significantly more frequent in the category of patients whose fetal position at full dilatation was not documented (7.2% for occiput posterior, 5.0% for occiput transverse, 5.8% for occiput anterior, and 18.1% for the missing positions).
Table 3 shows the mean duration of the second stage of labor according to fetal position and study group. We found that the policy had a modifying effect, with delayed pushing resulting in a prolongation of the duration of the second stage of labor. For women in the occiput posterior group advised to delay pushing, mean duration was 3.8 hours (95% CI 3.5–4.1) compared with 3.0 hours (95% CI 2.7–3.3) for those practicing early pushing (P < .001). For women in the occiput transverse group advised to delay pushing, mean duration was 3.6 hours (95% CI 3.3–3.9) for the delayed pushing group compared with 2.5 hours (95% CI 2.3–2.8) for the early pushing group (P < .001). For the occiput anterior group, mean duration was 3.1 hours (95% CI 3.0–3.2) for the delayed pushing group compared with 2.2 hours (95% CI 2.1–2.3) for the early pushing group (P < .001). The second stage of labor duration of patients with undocumented fetal position at full dilatation was similar, for the most part, to that of women in the occiput anterior group, with the exception of women with cesarean deliveries who were exposed to a policy of early pushing. In this category, labor duration was similar to that of women in the occiput posterior group.
Table 4 shows a multivariate logistic regression model of prolonged second stage of labor (> 3 hours). The model shows that the following are significant determinants of prolonged second stage of labor: fetal malposition at the beginning of the second stage (adjusted odds ratio [ORadj] 2.37, 95% CI 1.69–3.32, P < .001) for occiput posterior and (ORadj 1.57, 95% CI 1.13–2.18, P = .008) for occiput transverse; station of the fetal head at 0 at the beginning of the second stage (ORadj 1.45, 95% CI 1.15–1.84, P = .002); advanced maternal age (ORadj 2.83, 95% CI 1.91–4.20, P < .001) for women aged 35 years or older; birth weight of 4,000 g or higher (ORadj 1.85, 95% CI 1.32–2.61, P < .001); second-stage oxytocin administration (ORadj 1.45, 95% CI 1.18–1.78, P < .001). A policy of early pushing during the second stage had a protective effect on a prolonged second stage of labor (ORadj 0.26, 95% CI 0.22–0.32, P < .001).
Figures 1 and 2 graphically represent the difference in the duration of the second stage of labor for spontaneous vaginal deliveries according to fetal position in the delayed pushing group (Fig. 1) and in the early pushing group (Fig. 2), using Kaplan-Meier survival analysis. The x-axis represents the time elapsed in the second stage of labor expressed in minutes, and the y-axis the probability of continuation in labor beyond a given time. Censored data represent all second-stage cesarean deliveries and assisted vaginal deliveries.
Our study shows that fetal malposition at full dilatation is associated with longer second-stage labor and with an increase in a range of indicators of maternal morbidity.
The optimal strategy of management for the second stage of labor would allow the greatest probability of spontaneous delivery with the least risk of maternal and neonatal morbidity. There is, however, a lack of consensus regarding the optimum management of the second stage, including normal duration of second stage. It has been traditionally held that second-stage durations of greater than 2 hours place the baby at increased risk of adverse outcomes.29 More recent data suggest that with careful monitoring of fetal status, a prolonged second stage does not place the baby at increased risk.30–33
An ACOG Practice Bulletin has suggested that in the presence of epidural analgesia, second-stage durations of greater than 2 hours should be considered as prolonged.32 Our data provide partial support for this recommendation. For women experiencing spontaneous vaginal delivery who were advised to commence expulsive efforts at full dilatation (early pushing), the 90th percentile for second-stage duration was 3.0 hours, 2.8 hours, and 2.8 hours for occiput posterior, occiput transverse, and occiput anterior positions, respectively (data not shown). For women with spontaneous vaginal deliveries who were exposed to a policy of delayed pushing, the 90th percentile for the second-stage duration was 4.9 hours, 4.9 hours, and 3.9 hours for occiput posterior, occiput transverse, and occiput anterior positions, respectively (data not shown). For women experiencing operative delivery, the 90th percentile ranged from 4.6 hours (early pushing, occiput anterior position) to 6.3 hours (delayed pushing, occiput transverse position) (data not shown). Our results demonstrate that in nulliparous women under continuous epidural analgesia, the assessment of fetal position at full dilatation is an important determinant of second-stage duration. Guidelines that propose norms for expected labor duration should take into consideration position of the fetal head at full dilatation and the strategy of pushing. Our data suggest that the current recommendations of 2 hours for patients with epidural may be too restrictive, particularly when a policy of delayed pushing is practiced. With respect to maternal morbidity indicators, women in the “missing” category had rates that were intermediately between women in the occiput anterior group and those in the occiput transverse group, suggesting that the “missing” group was composed of a mix of fetal head positions.
Cephalohematoma was significantly more frequent in the “missing” group (16.9% missing compared with 4.5% occiput transverse compared with 5.0% occiput anterior compared with 6.7% occiput posterior; P < .001), whereas other forms of trauma were distributed similarly across groups. This could suggest that the fetuses in the missing category had significant molding at full dilatation that made the determination of the position more difficult and that also predisposed to the diagnosis of cephalohematoma.
In this low-risk obstetric population, the proportion of women with occiput posterior position at full dilatation was 13.1%, whereas the proportion was 12.4% for the occiput transverse position. A prospective study published as an abstract reported a 41.0% prevalence of occiput posterior positions and 44.5% of occiput transverse positions at hospital admission (Bernstein PC, Choi Y. Am J Obstet Gynecol 1999). In a prospective study using intrapartum sonography, Gardberg et al3 observed a prevalence of occiput posterior positions of 15% when women arrived in the delivery ward. Phillips and Freeman2 reported an incidence of occiput posterior positions of 10–20% early in labor, not specifying the precise moment that the head position was diagnosed. No separate data for occiput transverse positions early in labor were found in the literature.
Our results show no statistically significant differences in the duration of the first stage of labor according to fetal position at full cervical dilatation. Similarly, Gardberg et al3 and Calkins8 found no evidence of difference in the duration of the first stage between occiput anterior and occiput posterior positions diagnosed at delivery. Phillips and Freeman2 observed an increase of 84 minutes in the mean duration of the first stage of labor when the occiput posterior position persisted until delivery. No statistical analyses were mentioned.
The patient selection in this study could have resulted in a selection bias with respect to the absence of association between fetal position and the first stage of labor duration. Because our study assessed an approach to care in the second stage, patients having a first-stage cesarean delivery for slow labor progress were excluded.
We found a 46-minute increase in mean second-stage duration for patients with fetal malpositions at full dilatation compared with those in the occiput anterior positions. Phillips et al2 noted a 25-minute mean increase in the duration of the second stage of labor when the occiput posterior position of the fetal head persisted until delivery. Pearl et al's7 retrospective study found a statistically significant prolongation of the second stage of labor in persistent occiput posterior position deliveries (45.3 ± 46.5 minutes for occiput anterior compared with 60.1 ± 50.8 minutes for occiput posterior in spontaneous delivery, P < .05; and 117.9 ± 78.6 minutes for occiput anterior compared with 128.0 ± 76.6 minutes for occiput posterior in operative delivery, P < .05). Occiput transverse positions were not assessed in this study. Our findings of no significant differences in risk of abnormal Apgar scores or neonatal intensive care unit admission according to fetal position are similar to those of previous studies.2,3
Our observation of higher rates of severe perineal tears in women whose baby was in an occiput posterior and occiput transverse position is at least partly explained by higher incidences of midpelvic and rotational instrumental procedures. This observation is consistent with the results of previous studies.2 Calkin8 observed a frequency of 20% of injuries to soft tissues when the fetus had a posterior position during labor. The incidence of third-degree tear was 1.6% for posterior positions, compared with 10.0% in our study. Paradoxically, in Calkin's study, a higher rate of low forceps was reported: 65% compared with 8.1% in our study for posterior positions. In Calkin's publication, there was no comparison group.
It should be noted that most of the literature assessing the effects of fetal malposition has described the position of the presenting part at delivery,8,9,11,26 or has focused only on persistent occiput posterior positions (Bernstein PC, Choi Y. Am J Obstet Gynecol 1999).2,7,23,27 In our study, the position of the fetal head was documented at full dilatation. The position of the head at delivery was documented only in cases with forceps or vacuum. However, fetal position at the time of delivery was not documented for spontaneous vaginal deliveries. It was thus impossible to determine the proportion of women spontaneously delivering a baby in occiput posterior or occiput transverse position.
We observed a higher risk of estimated blood loss of more than 500 mL in the transverse and posterior positions group. This can be partially attributed to a higher rate of cesarean delivery in these groups. We verified whether fetal position was associated with a higher risk of blood transfusions. In our study, only 8 patients had blood transfusion (0.5% in occiput posterior, 1.0% in occiput transverse, 0.3% in occiput anterior, and 0.4% in the missing positions group).
In the trial on which this study was based, the indications for oxytocin treatment during the second stage of labor were standardized to minimize the potential for confounding by this variable. The epidural analgesia technique was also standardized.24 This should have avoided any confounding that could have resulted from imbalances in the epidural analgesia technique. Previous studies indicate that epidural increases the risk of fetal malposition at delivery.23 The motor block associated with epidural administration could cause pelvic muscle relaxation, which could prevent fetal rotation to an anterior rotation.28 In an observational study, the median duration of the second stage for nulliparous women experiencing spontaneous vaginal delivery was approximately 120 minutes in the presence of epidural as opposed to 60 minutes in its absence.20 Clinical trials comparing epidural to nonepidural forms of pain relief have also found epidural analgesia to prolong the second stage, and to increase the need for assisted vaginal delivery.16
In conclusion, the risk of maternal morbidity was significantly increased with occiput posterior and occiput transverse positions at full dilatation: cesarean delivery risk was increased by nearly 2-fold for occiput transverse and more than 4-fold for occiput posterior positions. Midpelvic procedures were increased almost by 3-fold with occiput posterior positions. Episiotomy and third- and fourth-degree tears were also increased in patients with occiput posterior and occiput transverse positions at full dilatation. Thus, fetal malposition is a risk factor for prolonged second stage as well as for maternal morbidity.
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2. Phillips RD, Freeman M. The management of the persistent occiput posterior position: a review of 552 consecutive cases. Obstet Gynecol 1974;43:171–7.
3. Gardberg M, Laakkonen E, Salevaara M. Intrapartum sonography and persistent occiput posterior position: a study of 408 deliveries. Obstet Gynecol 1998;91:746–9.
4. Oxorn H. Human labor and birth. 4th ed. New York (NY): Appleton-Century-Crofts, 1980. p. 725.
5. Cunningham FG, MacDonald PC, Gant NF, Leveno KJ, Gilstrap LC III. Williams obstetrics. 19th ed. Norwalk (CT): Appleton & Lange, 1993.
6. Schaal JP, Riethmuller D, Maillet R. Mécanique et techniques obstétricales. 2nd ed. Montpellier (France): Sauramps Médical; 1998.
7. Pearl ML, Roberts JM, Laros RK, Hurd WW. Vaginal delivery from the persistent occiput posterior position Influence on maternal and neonatal morbidity. J Reprod Med 1993;38:955–61.
8. Calkins L. Occiput posterior presentation. Obstet Gynecol 1953;1:466–71.
9. Haynes D. Occiput posterior position: six years’ experience at Parkland Hospital. JAMA 1954;156:494–6.
10. Kutcipal RA. The persistent occiput posterior position: a review of 498 cases. Obstet Gynecol 1959;14:296–304.
11. Hoult IJ, MacLennan AH, Carrie LE. Lumbar epidural analgesia in labor: relation to fœtal malposition and instrumental delivery. BMJ 1977;1:14–6.
12. MacLennan A. A template for defining a causal relation between acute intrapartum events and cerebral palsy: international consensus statement. BMJ 1999;319:1054–9.
13. Friedman EA. Labor: clinical evaluation and management. 2nd ed. New York (NY): Appleton-Century-Crofts; 1978. p. 450.
14. Howell CJ. Epidural versus non-epidural analgesia for pain relief in labor. Cochrane Database Syst Rev 2000;(2):CD000331. Review.
15. Howell CJ, Chalmers I. A review of prospectively controlled comparisons of epidural with non epidural forms of pain relief during labor. Int J Obstet Anaesth 1992;93:110.
16. Fitzpatrick M, Harkin R, McQuillan K, O'Brien C, O'Connell PR, O'Herlihy C. A randomised clinical trial comparing the effects of delayed versus immediate pushing with epidural analgesia on mode of delivery and faecal continence. Br J Obstet Gynaecol 2002;109:1359–65.
17. Saunders NJ, Spiby H, Gilbert L, Fraser RB, Hall JM, Mutton PM, et al. Oxytocin infusion during second stage of labor in primiparous women using epidural analgesia: a randomised double blind placebo controlled trial. BMJ 1989;299:1423–6.
18. Thorp JA, Eckert LO, Ang MS, Johnston DA, Peaceman AM, Parisi VM. Epidural analgesia and cesarean section for dystocia: risk factors in nulliparas. Am J Perinatol 1991;8:402–10.
19. Paterson CM, Saunders NS, Wadsworth J. The characteristics of the second stage of labor in 25,069 singleton deliveries in the North West Thames Health Region, 1988. Br J Obstet Gynaecol 1992;99:377–80.
20. Ramin SM, Gambling DR, Lucas MJ, Sharma SK, Sidawi JE, Leveno KJ. Randomized trial of epidural versus intravenous analgesia during labor. Obstet Gynecol 1995;86:783–9.
21. Robinson CA, Macones GA, Roth NW, Morgan MA. Does station of the fetal head at epidural placement affect the position of the fœtal vertex at delivery? Am J Obstet Gynecol 1996;175:991–4.
22. Thorp JA, Hu DH, Albin RM, McNitt J, Meyer BA, Cohen GR, et al. The effect of intrapartum epidural analgesia on nulliparae labor: a randomized, controlled, prospective trial. Am J Obstet Gynecol 1993;169:851–8.
23. Fitzpatrick M, McQuillan K, O'Herlihy C. Influence of persistent occiput posterior position on delivery outcome. Obstet Gynecol 2001;98:1027–31.
24. Fraser WD, Marcoux S, Krauss I, Douglas J, Goulet C, Boulvain M. Multicenter, randomized, controlled trial of delayed pushing for nulliparae women in the second stage of labor with continuous epidural analgesia The PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group. Am J Obstet Gynecol 2000;182:1165–72.
25. Turcot L, Marcoux S, Fraser W. Multivariate analysis of risk factors for operative delivery in nulliparae women. Canadian Early Amniotomy Study Group. Am J Obstet Gynecol 1997;176:395–402.
26. To WW, Li IC. Occipital posterior and occipital transverse positions: reappraisal of the obstetric risks. Aust N Z J Obstet Gynaecol 2000;40:275–9.
27. Gardberg M, Tuppurainen M. Persistent occiput posterior presentation—a clinical problem. Acta Obstet Gynecol Scand 1994;73:45–7.
28. Studd JW, Crawford JS, Duignan NM, Rowbotham CJ, Hughes AO. The effect of lumbar epidural analgesia on the rate of cervical dilatation and the outcome of labor of spontaneous onset. Br J Obstet Gynaecol 1980;87:1015–21.
29. Cohen W. Influence of the duration of second stage labor on perinatal outcome and puerperal morbidity. Obstet Gynecol 1977;49:266–9.
30. Moon JM, Smith CV, Rayburn WF. Perinatal outcome after a prolonged second stage of labor. J Reprod Med 1990;35:229–31.
31. Albers LL. The duration of labor in healthy women. J Perinatol 1999;19:114–9.
32. Dystocia and the augmentation of labor. ACOG Practice Bulletin No. 49. American College of Obstetricians and Gynecologists. Obstet Gynecol 2003;102:1445–54.
33. Fraser WD, Cayer M, Soeder BM, Turcot L, Marcoux S. PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group Risk factors for difficult delivery in nulliparas with epidural analgesia in second stage of labor. Obstet Gynecol 2002;99:409–18.
Other members of the Pushing Early Or Pushing Late with Epidural (PEOPLE) Study Group include:
William D. Fraser, MD, MSc
Sylvie Marcoux, MD, PhD
Isabelle Krauss, MD, MSc
Joanne Douglas, MD
Céline Goulet, RN, PhD
Investigators and research assistants:
J. Chabot, MD; J. Flammand, RN; L. Laperrière, BN. CHUQ-Pavillon St-François d'Assise, Québec, Québec, Canada.
P. Fish, MD; G. Hamel, RN. Hôpital de Chicoutimi, Chicoutimi, Québec, Québec, Canada.
R. Sabbah, MD; L. Vincelli. Hôpital Sacré-Cœur de Montréal, Montréal, Québec. Canada.
G. Tawagi, MD; O. Rosag, MD; J. Belcher, RN. Ottawa Civic Hospital, Ottawa, Ontario, Canada.
F. Galerneau, MD; M. Klein, MD; J. Swenerton, MD; B. Weibe, RN; E. Nickel, RN. BC Women's Hospital, Vancouver, British Columbia, Canada.
K. Milne, MD; J. Fuller, MD; L. Watson, RN. St-Joseph's Hospital, London, Ontario. Canada.
O. Irion, MD; K. Rifat, MD; V. Mentha (midwife). Hôpitaux Universitaires de Genève, Geneva, Switzerland.
S. Bottoms, MD; B. Steffy, RN. Hutzel Hospital, Detroit, Michigan, United States.
M. Helewa, MD; S. Lucy, MD; S. Erickson, RN. St-Boniface Hospital, Winnipeg, Manitoba, Canada.
N. Okun, MD; A. Guest, MD; A. Stuart, MD; D. Schimeck, RN. University of Alberta Hospital, Edmonton, Alberta, Canada.
M. Sermer, MD; M. Bailey, RN. Toronto General Hospital, Toronto, Ontario, Canada.
D. Blouin, MD; Y. Claprood, MD; D. Beaulieu, RN. Centre hospitalier universitaire de l'Estrie, Sherbrooke, Québec, Canada.
Data Management Committee:
Michel Boulvain, MD, PhD
Sylvie Bérubé, PhD
Safety and Efficacy Monitoring Committee:
François Meyer, MD, PhD
Aida Bairam, MD, PhD
Jean-Marie Moutquin, MD
© 2005 The American College of Obstetricians and Gynecologists
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