***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more OBJECTIVE To compare perinatal outcomes among women with epidural anesthesia who were encouraged to  push at complete dilatation with those who had a period of rest before pushing began . METHODS After a power analysis to determine appropriate sample size ( based upon an α error rate of .05 % and 80 % power ) , a prospect i ve r and omized trial of 252 women with epidural anesthesia was conducted . Patients were r and omized to a rest period or immediate pushing at complete dilatation . Variables measured included rate of fetal descent , length of time of pushing , the number and type of fetal heart rate decelerations , Apgar scores , arterial cord pH values , perineal injuries , type of delivery , length of second stage , maternal fatigue , and endometritis . RESULTS When a period of rest was used before pushing , we found a longer second stage , decreased pushing time , fewer decelerations , and , in primiparous women , less fatigue compared with control patients . Apgar scores , arterial cord pH values , rates of perineal injury , instrument delivery , and endometritis were similar in both groups . CONCLUSION Delayed pushing was not associated with demonstrable adverse outcome , despite second‐stage length of up to 4.9 hours . In select patients , such delay may be of benefit OBJECTIVE This study was undertaken to determine whether a policy of  delayed pushing  for nulliparous women with continuous-infusion epidural analgesia reduces the risk of difficult delivery ( cesarean delivery , operative delivery from a midpelvic position , low-pelvic procedures with rotation > 45 degrees ) . STUDY DESIGN In this multicenter , r and omized , controlled trial women in the delayed pushing group ( n = 936 ) were advised to wait > or = 2 hours after full dilatation before commencement of pushing .  Women in the early pushing group ( n = 926 ) were advised to commence pushing as soon as they had been r and omly assigned . RESULTS Difficult delivery was reduced with delayed pushing ( relative risk , 0.79 ; 95 % confidence interval , 0.66 - 0.95 ) . The greatest effect was on midpelvic procedures ( relative risk , 0.72 ; 95 % confidence interval , 0.55 - 0.93 ) . Although there was little evidence for an effect on low-pelvic procedures , spontaneous delivery was more frequent among women who practice d delayed pushing ( relative risk , 1.09 ; 95 % confidence interval , 1.00 - 1.18 ) . Abnormal umbilical cord blood pH ( < 7.15 venous value or < 7.10 arterial value ) was more frequent in the delayed pushing group ( relative risk , 2.45 , 95 % confidence interval , 1.35 - 4 . 43 ) . However , scores for a summary indicator , the Neonatal Morbidity Index , were similarly distributed in the 2 groups . CONCLUSION Delayed pushing is an effective strategy to reduce difficult deliveries among nulliparous women OBJECTIVE To determine if waiting for a strong urge to push in nulliparas with continuous low-concentration epidural analgesia  shortens the pushing duration in the second stage . METHODS Nulliparas with st and ardized patient-controlled epidural analgesia ( 0.0625 % bupivacaine with fentanyl 2 μg/mL ) were r and omly assigned to pushing immediately upon complete cervical dilatation ( n = 85 ) or waiting for a strong urge to push ( n = 117 ) . Urge to push and patient satisfaction were quantified on 100-mm visual analogue scales . Duration of pushing and total duration of the second stage were analyzed as survival time data . RESULTS Women who delayed pushing and those who pushed immediately were similar with respect to maternal characteristics . Women who delayed pushing had a stronger urge to push ( P < .01 ) and a longer second stage ( P < .05 ) than women who pushed immediately . There was no significant difference in the time spent pushing ( median 57 versus 62 minutes , respectively ) or the median level of patient satisfaction ( 80 mm for both groups ) . There were no significant differences in the overall rates of cesarean delivery ( 6 % versus 12 % , respectively ) , cesarean delivery during the second stage ( 2 % in each group ) , spontaneous vaginal delivery ( 70 % versus 69 % , respectively ) , or neonatal or maternal morbidity . CONCLUSION In nulliparas with continuous low-concentration  epidural analgesia , delaying pushing until a strong urge is felt does not reduce the duration of pushing in the second stage of labor Objective To identify the obstetric factors relating to anal sphincter injury at first vaginal delivery by prospect i ve cohort study of primiparous women . Methods We compared the results of a bowel function question naire and anal vector manometry before and 6 weeks after delivery in 184 primiparous women . Postpartum , pudendal nerve conduction latency was measured in all women , and anal endosonography was performed in 81 with altered fecal continence or abnormal physiology . Results Sixteen ( 9 % ) women , none of whom had altered fecal continence , were delivered by cesarean . After vaginal delivery , 42 of 168 ( 25 % ) women had impairment of fecal continence and 76 of 168 ( 45 % ) women had abnormal anal physiology . Instrumental vaginal delivery was associated with an 8.1-fold ( 95 % confidence interval [ CI ] 2.7 , 24.0 ; P < .001 ) risk of anal sphincter injury and a 7.2-fold ( 95 % CI 2.8 , 18.6 ; P < .001 ) risk of symptoms . Duration of the second stage of labor beyond 60 minutes led to a 1.7-fold ( 95 % CI 1.14 , 2.48 ; P ; < .01 ) risk of anal sphincter injury and a 1.6-fold ( 95 % CI 1.03 , 2.6 , P = .01 ) risk of symptoms .  Epidural analgesia , used in 58 % of vaginal deliveries , prolonged the second stage of labor ( P = .004 ; odds ratio [ OR ] 7.7 ; 95 % CI 4.0 , 14.7 ) and was associated with increased risk of sphincter injury ( P = .02 ; OR 2.1 ; 95 % CI 1.1 , 4.0 ) and of symptoms ( P = .02 ; OR 2.0 ; 95 % CI 1.1 , 3.7 ) . Conclusion Instrumental delivery and a second stage of labor prolonged by epidural analgesia are the obstetric factors that pose the greatest risk of injury to the anal sphincter mechanism in primiparous vaginal delivery Seventy-six primigravidae with epidural analgesia were r and omly assigned to one of two groups for management in the second stage . In one group the women delayed pushing and in the other they were managed conventionally . The two groups were well matched for maternal and infant characteristics , including position and level of the presenting part at full dilatation and fetal scalp blood pH. The mean waiting time in the second stage before pushing was increased from 27 min in the conventional group to 123 min in the delayed group . This delay was not associated with an increase in abnormal fetal heart rate abnormalities or any decrease in umbilical cord pH or Apgar scores . In contrast , the delay was associated with an increase in spontaneous deliveries and a decrease in forceps deliveries ( P = 0.06 ) . These findings suggest a need for redefining the management of the second stage of labour with epidural analgesia OBJECTIVE To determine if the use of delayed pushing after the onset of the second stage of labor decreases the time of active pushing and decreases maternal fatigue . DESIGN R and omized clinical trial . SETTING Labor and delivery unit of a not-for-profit community hospital . PATIENTS / PARTICIPANTS Convenience sample of nulliparous laboring women with epidural anesthesia . INTERVENTIONS Immediate or delayed pushing ( 2 hours ) during the second stage of labor at the time of complete cervical dilatation . MAIN OUTCOME MEASURES The length of pushing , total length of the second stage , and maternal fatigue . RESULTS A total of 77 women were studied ( immediate pushing group=39 ; delayed pushing=38 ) . The immediate pushing group averaged 94 ( ± 57 ) minutes in active pushing , while the delayed pushing group averaged 68 ( ± 46 ) minutes , a statistically significant difference ( p=.04 ) . No significant differences were found in fatigue scores between the immediate and delayed pushing groups ( p>.05 ) . CONCLUSIONS We found that by delaying the onset of active pushing for 2 hours after the beginning of the second stage of labor , the time that nulliparous women with epidural anesthesia spent in active pushing was significantly decreased by 27 % . Although the delayed pushing group rested for up to 2 hours , the total time in the second stage of labor averaged only 59 minutes longer than the immediate pushing group OBJECTIVE To compare outcomes between women receiving epidural anesthesia assigned to a group following either a 1-hour " delayed " pushing protocol or directed to initiate pushing at full cervical dilation . STUDY DESIGN Using a r and omized , controlled design , multivariate analyses were used to evaluate second stage labor duration and Apgar scores . An estimated odds ratio equation evaluated fetal descent progress . RESULTS A 13.68-minute difference occurred in second stage labor length ( p = 0.225 ) . No differences were found in Apgar scores ( p > 0.09 ) . An estimated odds ratio , that progress in terms of one fetal station unit would occur for control group subjects as compared with subjects with similar progress in the experimental group , was 1.51 ( 95 % confidence interval : 1.16 , 1.95 ) . CONCLUSION Second stage labor was not significantly lengthened , and a similar rate of fetal descent occurred in the absence of directed pushing . Findings support further research on the potential advantages of minimizing the duration of pushing in labor Objective To assess the effects of delayed vs immediate pushing  in second stage of labour with epidural analgesia on delivery outcome , postpartum faecal continence and postpartum anal sphincter and pudendal nerve function Background Although there are two methods of caring for women with epidural anesthesia during second-stage labor ( coached closed-glottis pushing immediately at 10-cm cervical dilation or delayed pushing until the woman feels the urge to push , passive fetal descent , and encouragement of open-glottis pushing when the woman has the urge to push ) , there are limited data concerning which method is most optimal for fetal well-being . Objective To evaluate effects on fetal well-being , as measured by fetal oxygen saturation , of two different methods of second-stage labor nursing care for women with epidural anesthesia . Methods Forty-five nulliparous women who had progressed to the second stage were r and omized to 1 of 2 groups ( immediate or delayed pushing ) .  Fetal oxygen saturation was continuously monitored and values at 10 cm , initiation of pushing and immediately prior to birth , as well as the amount of time that fetal oxygen saturation values were abnormal ( ≤30 % ) were compared between groups . Also evaluated were additional measures of fetal well-being such as fetal heart rate patterns , Apgar scores , and umbilical cord blood gases and maternal outcomes including length of labor , method of birth , and perineal status . Results There was a significant difference between groups in fetal oxygen desaturation during the second stage ( immediate : M = 12.5 ; delayed : M = 4.6 ) F(1 , 43 ) = 12.24 , p = .001 , and in the number of ≥2-min epochs of fetal oxygen saturation < 30 % ( immediate : M = 7.9 ; delayed : M = 2.7 ) , F(1 , 43 ) = 6.23 , p = .02 . There were more variable decelerations of the fetal heart rate in the immediate pushing group ( immediate : M = 22.4 ; delayed : M = 15.6 ) F(1 , 43 ) = 5.92 , p = .02 . There were no differences in length of labor , method of birth , Apgar scores , or umbilical cord blood gases . Women who pushed immediately had more perineal lacerations ( immediate : n = 13 ; delayed : n = 5 ) χ2(1 , N = 45 ) = 6.54 , p = .01 . Discussion Delayed pushing results in less fetal oxygen desaturation and less ≥2-min epochs of fetal oxygen saturation < 30 % during second-stage labor than the immediate pushing method ; thus , delayed pushing is more favorable for fetal well-being as measured by fetal oxygen saturation OBJECTIVES This study was undertaken to examine the national and regional rates of operative delivery among almost one quarter million births in a single year in the nation 's largest healthcare delivery system , using variation as an arbiter of the quality of decision making . STUDY DESIGN We compared the variation in  rates of  primary cesarean and operative vaginal delivery  in facilities of the Hospital Corporation of America during the year 2004 . RESULTS In 124 facilities representing almost 220,000 births during a 1-year period , the  primary cesarean and operative vaginal delivery rates were 19 % + /- 5 % ( range 9 - 37 ) and 7 % + /- 4 % ( range 1 - 23 ) . Within individual geographic 
    Output:
    
: Studies to date suggest there are few clinical differences in outcomes with immediate compared with delayed pushing in the second stage of labor , especially when high- quality studies are pooled .
Effects on maternal and neonatal outcomes remain uncertain