Henci Goer

Chapter 7: The Slow Labor (Literature Summaries)

• Gleanings from the Medical Literature
  • Nonmedical factors often determine the diagnosis and treatment of slow labor.
  • High-dose oxytocin regimens pose risks.
  • Active management is at worst, ineffective, and at best, unnecessary.
  • Active management does not eliminate the adverse effects of epidurals.
  • Simple, noninvasive strategies may safely and effectively enhance labor progress during the dilation and pushing phases of labor as well as make for a pleasanter labor.
  • Women admitted to the hospital in early or prelabor may be more likely to have labor interventions.
• References

Gleanings From the Medical Literature

Nonmedical factors often determine the diagnosis and treatment of slow labor.

A labor support professional describes the glaring discrepancies between nursing notes and mothers recall versus physicians notes for five clients previous cesareans.⁴² She writes that these cases are typical.

Case 1: the nurse charted complete cervical dilation, a head engaged in the pelvis, and the mother pushing well. The obstetrician wrote he performed the cesarean because the mother was 6 centimeters dilated and the head was high. The father remembered overhearing the obstetrician tell someone on the telephone to go ahead to the party; he would be there soon.

Case 2: the doctor told the mother she was too short for vaginal birth. In labor, he said she was not progressing satisfactorily and insisted that she have an epidural in case a cesarean was necessary. The nurse noted that she started the mother pushing before complete dilation and that she had been pushing for 35 minutes when the doctor decided on the cesarean. He recorded that she was fully dilated yet still had a cervical rim and that she had been pushing for 2 hours. The author comments that the nurse likely started the mother pushing early to try to forestall the cesarean.

Case 3: the doctor's notes contained nonsense statements such as "the patient never even separated." The nurse charted the baby's head as being 2 centimeters below what the doctors notes indicated. The mother had a cesarean after only an hour of pushing, even though she had had an epidural (epidurals slow pushing progress).

Case 4: the mother comments that she agreed to the cesarean only because she was told she had not dilated when, in fact, the nursing notes state she achieved 3-4 centimeters dilation.

Case 5: the mother felt no urge to push until they sat her up to do an epidural preparatory to a forceps delivery. They ignored her when she said she now had to push and continued with the epidural. The forceps attempt failed, and the doctor proceeded to a c-section.

Almost all hospitals plot labor progress on a graph that has centimeters dilation on the vertical axis and time on the horizontal axis. Researchers found that changing how data looked on the graph could alter obstetrician recommendations.¹³ They gave 16 obstetricians six hypothetical equivocal cases sufficiently separated in time that the doctors would not realize they were seeing the same cases twice. In three cases, researchers made it appear that labor was taking longer by increasing the distance between time marks on the horizontal axis in one of the pair. In the other three cases, they either graphed early labor along with active labor or graphed active labor only and described early labor in the case notes. Out of 96 decisions, the presentation that visually suggested longer labor resulted in 14 more recommendations for c-section, 5 more for instrumental delivery, and 11 more for giving oxytocin.

Intervention rates vary according to the individual practitioner's personal approach. Researchers looked at management according to whether 11 obstetricians had a low, medium, or high cesarean rate.¹⁵ Cesarean rates for poor progress ranged from 3% to 16% in low-risk first-time mothers despite similar maternal and infant characteristics. While doctors in the low cesarean-rate group induced labor less often and started oxytocin later in labor, they also used oxytocin more often and in higher doses. From this the authors conclude that oxytocin is the key to reducing cesareans, which, as midwifery statistics attest, isnt so. Another study grouped 550 first-time mothers according to whether their doctors cesarean rate for poor progress was low (6-7%) or high (9-15%).²⁷ Women in both groups were equally likely to have epidurals, oxytocin, and to have doctors rupture membranes, all factors influencing progress. However, doctors in the high cesarean-rate group were more than three times as likely (2.5% versus 8%) to perform a cesarean for poor progress during pushing. Eight babies in the low cesarean-rate group had broken collarbones or facial nerve injuries from forceps deliveries. The authors comment that these might have been avoided by allowing more time to push.

Cesarean rates also vary by practice type (see also p.257 "Active management is at worst . . ."). A study of clinic and private obstetricians at a single hospital found that among 200 healthy, first-time mothers, the cesarean rate for poor progress was 1% on the clinic service and 20% on the private service, although women were equally likely to have epidurals (42% in both groups).⁴¹ Women not having epidurals were more likely to have oxytocin on the private service (32% versus 20%), yet they were 14 times more likely to have cesareans compared with clinic women not having epidurals. Women having epidurals with private doctors were as likely to have oxytocin as clinic women, yet, they too were 14 times more likely to have a cesarean. Researchers in another study compared cesarean rates at a hospital that had private doctors, clinic doctors serving low-income women, and HMO doctors working shifts.³⁷ So that poor progress would be the main reason for cesareans, they looked at low-risk first-time mothers. Rates were 21% for private physicians, 17% for clinic physicians, and 15% for HMO physicians. After taking epidural use into account, women with HMO doctors were less than half as likely to have a cesarean as women with private obstetricians. Interestingly, the study was done a year after the HMO formed. Two years later, there had been a "marked" increase in HMO cesarean rates, which suggests that hospital cultural climate affected practice.

Convenience is a factor. A study of cesarean for poor progress in 4,200 first-time mothers found that more cesareans were performed in the evening than at night during sleep hours or during the day when obstetricians had office hours and scheduled surgeries.²² A study comparing first-time (primary) cesarean rates among three hospitals with private physicians and one with salaried physicians working shifts found that fewer cesareans for poor progress were done at two of the private hospitals at night than during the day or evening.¹⁹ This did not occur at the hospital where doctors worked shifts or at the other private hospital. Cesarean rates were 6% at the hospital with shifts versus 9% at the private hospital where time of day did not matter and 11% at the hospitals where it did.

High-dose oxytocin regimens pose risks.

The major risk of high-dose oxytocin regimens is uterine hyperstimulation, that is, overly long, frequent, and strong contractions along with overly high uterine-muscle tension in between contractions. Hyperstimulation reduces the baby's oxygen supply, which can cause fetal distress. Researchers at a hospital using a high-dose protocol found that babies were twice as likely to be born with low blood pH, a symptom of oxygen deprivation in labor, when the mother had oxytocin.³² Several comparisons of high-dose versus low-dose protocols and protocols with short intervals between dose increases versus protocols that have longer intervals between dose increases have found that more women experience hyperstimulation and fetal distress with high-dose, and/or short-interval regimens (see also p.229).^20,33,47 In one trial of active management, seven women, more than one-third, experienced hyperstimulation, and one had a cesarean for fetal distress.⁵ In another trial, staff ignored a case of hyperstimulation, and the baby died.⁵³ The National Maternity Hospital obstetricians conducted a large study (13,000 labors) of electronic fetal monitoring in which they found that newborn seizures, the strongest evidence of oxygen deprivation in labor, were associated with oxytocin use and longer labors, the very labors for which active management prescribes oxytocin.³⁸ In another active managment study, nurses did not turn down the oxytocin as protocol dictated in 4% of the women experiencing hyperstimulation. If staff ignore hyperstimulation 4% of the time in a hospital with a standardized protocol, what might the percentage be under less controlled circumstances?¹

Oxytocin-caused hyperstimulation may be a particular problem when the baby has passed large amounts of stool (thick meconium) into the amniotic fluid. The danger with meconium is that the baby will inhale it and develop a life-threatening pneumonia. Researchers studied 250 women with thick meconium whose labors stopped progressing and whose babies were not in distress.⁴⁰ Over 40% of women given oxytocin who later had a cesarean for fetal distress had babies who inhaled meconium versus 6% of babies of mothers given oxytocin who went on to vaginal birth, a percentage comparable to the 5% who had cesareans and no oxytocin. The authors speculated that when oxytocin caused uterine hyperstimulation, the baby's oxygen level dropped, causing the baby to reflexively gasp in meconium.

Active management is at worst, ineffective, and at best, unnecessary.

While several before-and-after studies have shown statistically significant (meaning unlikely to be due to chance) reductions in cesarean rates with high-dose oxytocin regimens, four trials randomly assigning women to active management or standard management have not.^10,23,35,44 It is a truism that treatments almost always look better in nonrandomized trials because randomized controlled trials eliminate many sources of bias. For example, with before-and-after trials, the intent to lower the cesarean rate and the belief that the new protocol will work can become a self-fulfilling prophecy.

Two analyses of outcomes from multiple randomized controlled trials (meta-analysis) agree that rupturing membranes and aggressive use of oxytocin offer no benefits. In one, researchers evaluated data from trials of the components of active management to determine their efficacy.⁵² Rupturing membranes (amniotomy) shortened labor somewhat but didn't lower cesarean or instrumental delivery rates. Early use of oxytocin increased pain and uterine hyperstimulation, but conferred no benefits. Combining liberal oxytocin use with rupturing membranes shortened labor, but still didn't decrease cesarean or instrumental deliveries. By contrast, a female labor companion (doula) reduced the use of pain medication, instrumental delivery, and c-section and improved the condition of babies at birth. The authors concluded that female labor companions appeared to be the effective component of active management. In the other meta-analysis, researchers collected 12 trials of active management versus usual care totalling 5,100 women.²¹ They, too, found a reduction in labor length but no reduction in instrumental or cesarean delivery rates with active management. Some of the trials suggested that active management increased epidural and hemorrhage rates.

A developer of active management analyzed the usefulness of active management and concluded that active management shortened labor overall by shortening early labor, which normally proceeds at a leisurely pace. Active management had no effect on active labor, the phase of labor where a slow down or halt indicates a possible problem.⁹ Undeterred, he and his co-author converted this to a benefit by declaring slow dilation in early labor to be inefficient and correctable by application of active management.

Taken together, four small randomized controlled trials, 169 women in all, show that compared with less aggressive management, active management also fails as treatment for longer delays in progress than one hour, the usual delay that triggers oxytocin use.^6,21 Overall, the cesarean rate was 20% in the active management group versus 19% in the conservatively managed group.

A randomized-controlled trial of active management in first-time mothers illustrates how cesarean rate depends largely on physician philosophy.³⁵ Overall cesarean rates differed only slightly between active management and usual care groups: 11% in the active management group and 14% in the standard care group. A critique of this study points out that the cesarean rate in first-time mothers the year before the study was 23%.⁴⁵ This means merely doing the study decreased cesarean rates by 40% in women receiving usual care! Furthermore, active management only benefited patients of private physicians. The cesarean rate in clinic patients was 9% in both active management and standard care groups. The cesarean rate in clinic patients had been 17% the year before, so while active management didn't reduce the cesarean rate in low-income women, doing a study halved it. Incredibly, the trial's authors explained the difference between private and clinic patients by saying that active management seemed especially effective in private patients, a group recognized as being at increased risk for dysfunctional labors. Since all participants, rich or poor, were healthy, first-time mothers who started labor on their own, the authors are claiming that having enough money to afford private care causes dysfunctional labor.

Giving women more time works just as well at reducing cesareans. In another randomized controlled trial, also a study of first-time mothers, cesarean rates did not differ even though women were 20% more likely to have an epidural (64% versus 54%) in the usual care group.²³ What differed was that women were three times more likely to have labors lasting more than 12 hours in the usual care group (26% versus 9%).

Active management does not eliminate the adverse effects of epidurals.

Half of the first 1,000 first-time mothers to give birth at the Dublin National Hospital in 1992 had epidurals versus 1% of the first 1,000 first-time mothers in 1973. The cesarean rate, which was 5% in 1973, had doubled to 10% in 1992.⁸ Another study of 9,000 first-time mothers giving birth at the Dublin National Hospital in 1990-1994 reported that while the overall cesarean rate was 11%, it was 24% among women having prolonged labor of whom 90% had epidurals.³⁶ An additional 40% of women with prolonged labor had an instrumental delivery (the active management protocol limits pushing phase to 2 hours). Having an epidural increased the likelihood of having a prolonged labor six-fold, 42-fold if the epidural was placed early in labor. A U.S. study of active versus standard management in 400 first-time mothers found that even though active management helped women with epidurals somewhat, the cesarean rate was still 11% versus 3% in women not having an epidural.⁴⁴ Over 85% of all cesareans were in women who had epidurals.

Simple, noninvasive strategies may safely and effectively enhance labor progress during the dilation and pushing phases of labor as well as make for a pleasanter labor.

I have five studies that compared walking and staying upright in labor with lying in bed and two studies comparing walking with oxytocin augmentation for slow labors. All that can be said for certain is that none found any harm in allowing freedom of activity and position, a statement that cannot be made of oxytocin, and that women who walked liked it -- 99% in a large study that asked women about this.⁷ Beyond that it is difficult to draw firm conclusions because the studies all have problems. For example, one major confounding factor is that women could choose whether and how long to walk. The reasons why women would agree or decline to walk and how long they walked would undoubtedly have to do with the kind of labor they were having, which, in turn, could affect whether walking seemed to help or not. It could go either way. Women having more painful, nonprogressive labors with, say, a posterior baby might prefer to lie down as might women in intense, rapidly progressing labors. A recent, large trial randomly assigning women to walk or not found that women who declined walking had shorter labors, which suggests that the second possibility was the case.⁷

Three studies concluded that walking had benefits, two of them that first-time mothers had the most to gain. Two trials, one of 370 women and one of only 40 women, that assigned women to walk or to bedrest groups found that first-time mothers who walked shortened labor by about 1 1/2 hours compared with the group assigned to bed rest.^3,16 A third study analyzed the effect of walking and staying upright in 1,700 women attended by midwives.² Women who stayed upright had half the rate of instrumental and cesarean delivery combined (3% versus 6%). Labor was not shortened, but the midwives recommended walking to women making slow progress.

The two largest studies, both random assignment trials, found no benefit. The first, of 630 women, found no reductions in oxytocin use, instrumental delivery, or cesarean section.²⁹ However, only about half of women in the walking group walked in early labor and virtually none walked in late labor. The other, involving 1070 women, found no differences in length of labor, use of oxytocin or pain medication, or instrumental or cesarean delivery.⁷ This held true for both first-time mothers and women with prior births. However, in the walking group, nearly one-quarter never walked at all, and of women who walked, half walked less than an hour.

Both studies of walking versus oxytocin for slow labor showed benefits. In one, 14 women were assigned to either walking or oxytocin.⁴³ In the first hour, all eight walking women made progress in dilation and descent of the fetal head versus three of six women having oxytocin. In the second hour, one woman in the walking group gave birth and the rest made further progress versus four women in the oxytocin group. Oxytocin increased pain whereas walking lessened it or made no difference. The second study, of 57 women, found that 60% of women in the walking group gave birth without requiring oxytocin.³¹ Women in the oxytocin group reported more pain and experienced more excessively strong contractions.

Researchers in one study randomly assigned 84 women to labor augmentation either by nipple stimulation via breast pump or oxytocin.⁴⁹ Nipple stimulation alone succeeded in half the women and achieved similar average labor duration and fewer cesareans compared with oxytocin. This was despite lower contraction pressures in the nipple stimulation group, a potential advantage in that lower pressures could minimize pain and the possibility of fetal distress. (See also p.228.)

Of five studies of women randomly assigned to either upright or lying-down pushing positions, four reported some benefit. In the one that didnt, only six first-time mothers and five mothers with prior births actually squatted, numbers too small to draw any conclusions.²⁸The other studies all involved at least 300 participants. All three studies that evaluated pain and preference found that women liked the upright position and experienced less pain.^14,24,54 One study found less genital injury.²⁴ Two found that upright positioning shortened pushing phase and one that it resulted in fewer instrumental deliveries (9% versus 16%).^24-25 One in which upright women used a birthing stool reported more blood loss in the upright group, but the authors acknowledged that blood-loss estimates are subjective.⁵⁴ On the birth stool, blood collected in a bowl under the stool whereas in bed, some blood soaked into pads and sheets. In a sixth study, in one practice, researchers randomly selected case records of women who squatted to push and compared outcomes with randomly selected records from another practice offering similar labor care except that women gave birth semi-sitting.²⁶ Researchers found less genital injury, shorter pushing phase, and less use of instrumental delivery in first-time mothers (8% versus 17%) in the squatting group.

I have six studies evaluating warm tub baths in labor. A randomized trial of 110 first-time mothers found a significant improvement in cervical softening and effacement and a trend toward faster dilation in the bath group.¹² Compared with nonbathers, bathing stabilized pain intensity for about half an hour before it began to rise again. Eighty percent of bathers said the bath soothed pain and relaxed them, and 90% would want to bathe in a future labor. Women also tended to have oxytocin less often. Another study compared outcomes between 88 women taking a 1 1/2 to 2 hour bath with 72 similar women who chose not to bathe.³⁴ Bathers dilated twice as fast in the bath. They hurt more before the bath and experienced greater pain relief from the bath compared with nonbathers. Nonbathers were more likely to have narcotic pain relief and twice as likely to have oxytocin. However, this study did not involve random assignment, so there may well be confounding factors. In the third study, researchers compared 89 bathers with 89 similar nonbathers and found that bathers were less likely to receive oxytocin or to have pain medication, but this may be because bathers were participants in a study of in-hospital homestyle care whereas nonbathers received standard care.⁵⁵ Researchers in a fourth study randomly assigned 800 women to be offered a bath or not.⁴⁶ Only half the women in the bath group actually bathed and these were more likely to be first-time mothers with less cervical dilation. This may explain why bathing did not shorten labor or lessen oxytocin use. Bath-group women were 25% less likely to use pain medication. Bathers reported that the tub relieved pain and helped them relax. The fifth study found no benefit in 45 women who bathed in labor verus 48 who didn't.⁴⁸ In the sixth study, researchers randomly assigned 200 women to bathe either early, before 5 cm dilation, or late, after 5 cm dilation.¹⁸ The early bathers averaged longer labors. However there were more first-time mothers in the early bath group (72% versus 60%), and early bathers were more likely to have epidurals (27% versus 9%), both factors that make for slower labors. And if there were an effect, it could be either that early bathing slowed labor or late bathing speeded it up.

None of these six studies plus a seventh that only evaluated infection rates in 540 bathers versus 850 nonbathers found an increased risk of maternal or infant infection.¹⁷ This was despite the fact that all women had ruptured membranes in three of the studies.^12,17,55

Women admitted to the hospital in early or prelabor may be more likely to have labor interventions.

Researchers found that among 600 healthy, first-time mothers, women laboring slowly who arrived at the hospital earlier in labor were more likely to have a diagnosis of difficult delivery (12% versus 3%), oxytocin augmentation (45% versus 30%), instrumental delivery (14% versus 9%), and c-section (16% versus 4%) than women laboring slowly who came later in labor.³⁰ For women making rapid progress, time of arrival made no difference. Protracted labor was the reason for cesarean in seven early comers but no late comers regardless of progress rate. Researchers in another study compared outcomes in 3,800 first-time mothers at four hospitals.⁵⁰ Cesarean rates ranged from 12% to 20% (average: 16%), of which three-quarters were done for poor progress. Forty percent of all cesareans were done in early labor. The authors concluded that if doctors would stop doing cesareans before active phase labor and for poor progress in the absence of fetal distress, the average cesarean rate could be halved. A third study found that use of oxytocin to augment labor declined linearly from over three-quarters of women admitted at 1 centimeter dilation or less to less than 20% of women admitted at 5 centimeters dilation or more.¹¹ Epidural use was also strongly and inversely associated with both dilation at admission and labor augmentation. The authors of a random assignment trial in first-time mothers noted that the cesarean rate for women admitted at less than 3 centimeters dilation was 10% versus one-tenth that percentage in women admitted at 3 centimeters dilation or more.¹⁰

Two other studies have also reported that women who experience "false labor" are more likely to have oxytocin induction, augmentation, and cesarean section.^4,51 Their authors concluded that women experiencing false labor were at high risk for dysfunctional labor. An equally plausible explanation is that impatience leads to a diagnosis of prolonged labor and inappropriate intervention, including cesarean section.

Finally, a trial in which over 200 women with prelabor or early labor contractions were randomly assigned to hospital admission or to be sent home found that women who were sent home were less than half as likely to be given oxytocin.³⁹ This study is especially important because random assignment ensures that the two groups are truly similar. While cesarean rates overall were not significantly different, meaning the difference was considered due to chance, one-quarter (2 of 8) of the cesareans were done for dysfunctional labor in the group sent home versus three-quarters (8 of 11) of the cesareans in the admitted group. This occurred despite the fact that 16% of women in the "admit" group actually got sent home, and most women had epidurals in both groups, factors that would tend to flatten out differences between them.

References

1. Akoury HA et al. Oxytocin augmentation of labor and perinatal outcome in nulliparas. Obstet Gynecol 1991;78(2):227-230.

2. Albers LL et al. The relationship of ambulation in labor to operative delivery. J Nurse Midwifery 1997;42(1):4-8.

3. Andrews CM and Chrzanowski M. Maternal position, labor and comfort. Applied Nursing Res 1990;3(1):7-13.

4. Arulkumaran S et al. Obstetric outcome of patients with a previous episode of spurious labor. Am J Obstet Gynecol 1987;157(1):17-20.

5. Bidgood KA and Steer PJ. A randomized control study of oxytocin augmentation of labour. 1. Obstetric outcome. Br J Obstet Gynaecol 1987;94:512-517.

6. Blanch G et al. Dysfunctional labour: a randomised trial. Br J Obstet Gynaecol 1998;105(1):117-20.

7. Bloom SL et al. Lack of effect of walking on labor and delivery. N Engl J Med 1998;339(2):76-9.

8. Boylan P, Robson M, and McParland P. Active management of labor. Am J Obstet Gynecol 1993;168(1 Pt 2):295.

9. Boylan PC and Parisi VM. Effect of active management on latent phase labor. Am J PerinatolMed 1990;7(4):363-5.

10. Cammu H and Van Eeckhout E. A randomised trial of early versus delayed use of amniotomy and oxytocin infusion in nulliparous labour. Br J Obstet Gynaecol 1996;103(9):939-40.

11. Cammu H et al. Epidural analgesia in active management of labor. Acta Obstet Gynecol Scand 1994;73:235-9.

12. Cammu H et al. "To bathe or not to bathe during the first stage of labor". Acta Obstet Gynecol Scand 1994;73:468-72.

13. Cartmill RSV and Thornton JG. Effect of presentation of partogram information on obstetric decision-making. Lancet 1992;339:1520-2.

14. de Jong PR et al. Randomised trial comparing the upright and supine positions for the second stage of labour. Br J Obstet Gynaecol 1997;104(5):567-71.

15. DeMott RK and Sandmire HF. The Green Bay cesarean section study. II. The physician factor as a determinant of cesarean birth rates for failed labor. Am J Obstet Gynecol 1992;166(6 Pt 1):1799-1810.

16. Diaz AG et al. Vertical position during the first stage of the course of labor, and neonatal outcome. Eur J Obstet Gynecol Reprod Biol 1980;11:1-7.

17. Eriksson M et al. Warm tub bath during labor. A study of 1385 women with prelabor rupture of the membranes after 34 weeks of gestation. Acta Obstet Gynecol Scand 1996;75:642-4.

18. Eriksson M, Mattsson LA, and Ladfors L. Early or late bath during the first stage of labour: a randomised study of 200 women. Midwifery 1997;13:146-8.

19. Evans MI et al. Cesarean section: assessment of the convenience factor. J Reprod Med 1984;29(9):670-676.

20. Foster TCS, Jacobson JD, and Valenzuela GJ. Oxytocin augmentation of labor: a comparison of 15- and 30-minute dose increment intervals. Obstet Gynecol 1988;71(2):147-9.

21. Fraser W et al. Effects of early augmentation of labour with amniotomy and oxytocin in nulliparous women: a meta-analysis. Br J Obstet Gynaecol 1998;105(2):189-94.

22. Fraser W et al. Temporal variation in rates of cesarean section for dystocia: does convenience play a role? Am J Obstet Gynecol 1987;156(2):300-304.

23. Frigoletto FD et al. A clinical trial of active management of labor. New Engl J Med 1995;333(12):745-50.

24. Gardosi J, Hutson N, and B-Lynch C. Randomized controlled trial of squatting in the second stage of labour. Lancet 1989;2(8654):74-77.

25. Gardosi J, Sylvester S, and B-Lynch C. Alternative positions in the second stage of labour: a randomized controlled trial. Br J Obstet Gynaecol 1989;96:1290-1296.

26. Golay J, Vedam S, and Sorger L. The squatting position for the second stage of labor: effects on labor and on maternal and fetal well-being. Birth 1993;20(2):73-8.

27. Guillemette J and Fraser WD. Differences between obstetricians in caesarean rates and the management of labour. Br J Obstet Gynecol 1992;99(2):105-108.

28. Gupta JK, Brayshaw EM, and Lilford R. An experiment of squatting birth. Eur J Obstet Gynecol Reprod Biol 1989;30:217-20.

29. Hemminki E and Saarikoski S. Ambulation and delayed amniotomy in the first stage of labor. Eur J Obstet Gynecol Reprod Biol 1983;15:129-39.

30. Hemminki E and Simukka R. The timing of hospital admission and progress of labour. Eur J Obstet Gynecol Reprod Biol 1986;22:85-94.

31. Hemminki E et al. Ambulation versus oxytocin in protracted labour: a pilot study. Eur J Obstet Gynecol Reprod Biol 1985;20:199-208.

32. Herbst A, Wolner-Hanssen P, and Ingemarsson I. Risk factors for acidemia at birth. Obstet Gynecol 1997;90(1):125-30.

33. Lazor LZ et al. A randomized comparison of 15- and 40-minute dosing protocols for labor augmentation and induction. Obstet Gynecol 1993;82(6):1009-12.

34. Lenstrup C et al. Warm tub bath during delivery. Acta Obstet Gynecol Scand 1987;66(8):709-12.

35. Lopez-Zeno JA et al. A controlled trial of a program for the active management of labor. N Engl J Med 1992;326(17):450-454.

36. Malone FD et al. Prolonged labor in nulliparas: lessons from the active management of labor. Obstet Gynecol 1996;88(2):211-5.

37. McCloskey L, Petitti DB, and Hobel CJ. Variations in the use of cesarean delivery for dystocia: lessons about the source of care. Med Care 1992;30(2):126-135.

38. McDonald D et al. The Dublin randomized controlled trial of intrapartum fetal heart rate monitoring. Am J Obstet Gynecol 1985;152(5):524-539.

39. McNiven PS et al. An early labor assessment program: a randomized, controlled trial. Birth 1998;25(1):5-10.

40. Morel MIG et al. Oxytocin augmentation in arrest disorders in the presence of thick meconium: influence on neonatal outcome. Gynecol Obstet Invest 1994;37(1):21-4.

41. Neuhoff D, Burke MS, and Porreco RP. Cesarean birth for failed progress in labor. Obstet Gynecol 1989;73(6):915-920.

42. Perez P. The patient observer: what really led to these cesarean births? Birth 1989;16(3):130-9.

43. Read JA, Miller FC, and Paul RH. Randomized trial of ambulation versus oxytocin for labor enhancement: a preliminary report. Am J Obstet Gynecol 1981;139(6):669-672.

44. Rogers R et al. Active management of labor: does it make a difference? Am J Obstet Gynecol 1997:177(3):599-605.

45. Rothman BK. The active management of physicians. Birth 1993;20(3):158-159.

46. Rush J et al. The effects of whirlpool baths in labor: a randomized, controlled trial. Birth 1996;23(3):136-43.

47. Satin AJ et al. High- versus low-dose oxytocin for labor stimulation. Obstet Gynecol 1992;80(1):111-116.

48. Schorn MN, McAllister JL, and Blanco JD. Water immersion and the effect on labor. J Nurse Midwifery 1993;38(6):336-42.

49. Stein JL et al. Nipple stimulation for labor augmentation. J Reprod Med 1990;35(7):710-4.

50. Stewart PJ et al. Diagnosis of dystocia and management with cesarean section among primiparous women in Ottawa-Carleton. Can Med Assoc J 1990;142(5):459-463.

51. Summers PR et al. Pregnancy outcome in patients with repeat visits to the labor observation area near term. South Med J 1991;84(4):436-438.

52. Thornton JG and Lilford RJ. Active management of labour: current knowledge and research. BMJ 1994;309(6951):366-9.

53. Turner MJ, Brassil M, and Gordon H. Active management of labor associated with a decrease in the cesarean section rate in nulliparas. Obstet Gynecol 1988;71(2):150-154.

54. Waldenstrom U and Gottvall K. A randomized trial of birthing stool or conventional semirecumbent position for second-stage labor. Birth 1991;18(1):5-10.

55. Waldenstrom U and Nilsson CA. Warm tub bath after spontaneous rupture of the membranes. Birth 1992;19(2):57-63.

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