Commentary and Review by:

R. Daniel Braun, MD
OBGYN.net International Representative for the United States
R.Daniel.Braun@obgyn.net

With additional comments from Dr. Malcolm Griffiths <Malcolm@mgriff22.demon.co.uk>

Title: Active management of labor: Does it make a difference?

Ref: Am J Obstet Gynecol 1997;177:599-605

Authors: Rebecca Rogers, George J.Gilson, Anthony C. Miller, Luis E. Izquierdo, Luis B. Curet, & Clifford R. Qualls

Institution: University of New Mexico Health Sciences Center, Albuquerque, NM

Study Design: Randomized Controlled Clinical Trial

Rating:

Abstract:

Objective: Our goal was to evaluate whether active management of labor lowers cesarean section rates, shortens the length of labor, and overcomes any negative effects of epidural analgesia on nulliparous labor.

Study Design: We randomly assigned 405 low risk term nulliparous patients to either an active management of labor (n=200) or our usual care protocol(n=205). Patients who were undergoing active management of labor were diagnosed as being in labor on the basis of having painful palpable contractions accompanied by 80% cervical effacement, underwent early amniotomy, and were treated with high-dose oxytocin for failure toprogress adequately in labor.

Results: The cesarean section rate in the active management of labor group was lower than that of controls but not significantly so (active management, 7.5%; controls, 11.7%; p=0.36). The length of labor in the active management group was shortened by 1.7 hours (from 11.4 to 9.7 hours; p=0.001). Fifty-five percent of patients received epidural analgesics; a reduction in length of labor persisted despite the use of epidural analgesics (active management11.2 hours vs. control 13.3 hours, p=0.001). A significantly greater proportion of active management patients were delivered by 12 hours compared with controls (75% vs. 58%, p=0.01); this difference also persisted despite the use of epidural analgesics (66% vs. 51%, p=0.03).

Conclusions: Patients undergoing active management had shortened labors and were more likely to be delivered within 12 hours, differences that persisted despite the use of epidural analgesics. There was a trend toward a reduced rate of cesarean section.

Commentary

To begin with the authors are to be congratulated for performing a quality study on a large number of patients. This study required a large amount of time and effort. It was well designed. A pre study power analysis was even carried out.

That said, we can get down to picking nits. My first and perhaps biggest nit is the term; "Active management of labor". In the introduction, the authors state:" We designed a prospective randomized trial to evaluate the efficacy of early amniotomy and of high-dose oxytocin in lowering
cesarean section rates in nulliparous women in a university hospital setting. Our population's high epidural use reflects the analgesia preferences of many laboring patients in this country. We evaluated whether active management of labor (italics for my emphasis) would shorten labor lower cesarean section rates, and overcome any negative effects epidural analgesia might have on labor in nulliparous women." They indeed designed a trial to evaluate the efficacy of early amniotomy and of high-dose oxytocin in lowering cesarean section rates in nulliparous women in a university hospital setting. However, from my reading and understanding, early amniotomy and high dose oxytocin are
only a small part of "Active management of labor" (AML)1 AML as practiced in Dublin seems to me to be more of an approach to labor than any specific protocol. This approach seems to include: requiring a diagnosis of labor before admission to the labor unit, very close observation of the laboring patient by both the midwife and the attending physician(neither one of whom are outside the labor unit), early amniotomy, early use of high-dose oxytocin to treat labor abnormalities, antenatal preparation, and continuous personal attention during labor. AML also defines duration of labor as the number of hours a woman spends on the labor unit from admission to delivery. The average duration of nulliparous labor in Dublin is six hours with 98% being delivered by 14 hours and 100% by 14 hours. If the mother is not close to easy vaginal delivery at the end of 12 hours, she is subjected to a cesarean section. In spite of this policy, the cesarean section rate remained below 5% until 1985 when it became 5.1%. It increased to 8.5% in 1990 and 1992.

With that rapid overview of AML Dublin style in mind, let's look at the study protocol and the control protocols used in the current study.

  Study Group Control Group
Dx of Labor Regular painful uterine contractions every 2-5 minutes in a patient who is at least 80% effaced, regardless of dilatation. 3-4 cm dilated regardless of effacement in conjunction with regular painful uterine contractions every 2-5 minutes
Amniotomy Within 2 hours of admission At the discretion of the attending physician.
Need for Augmentation Cx. Dil.<1Cm/hr. in 1st stage or descent <1Cm/hr. in 2nd stage Cx change of <1.25 cm/hr once active phase has begun.
Oxytocin Augmentation 6mU/min Increasing every 15 min. til 7 contrx. In 15 min. or adequate Cx. Change. Max=36mU/min. 1 mU/min. increased by 1 mU/min every 30-40 min to achieve and maintain adequate uterine activity as defined here. (I could not find the definition) Max=36mU/min.

Electronic fetal monitoring was routinely used in both groups and both groups had one Labor and Delivery Nurse assigned to 2 laboring patients at any one time.

Eligible patients were nulliparous women at term pregnancy who were examined in the antenatal testing unit and who had painful, palpable uterine contractions 5 minutes or less apart, with cervical effacement of at least 80%. Randomization was based on a computer generated list of random numbers and were assigned by sealed opaque envelopes. After 2 multiparous patients who had been included by mistake were dropped, there were 200 patients assigned to the study group and 205 to the control group. This number was determined based on a power study which determined that 390 patients would be needed to demonstrate with 80% power a reduction of the cesarean rate from 14.5% (the rate at UNM) to 5.5% reported by O'Driscoll et al.2 This assumption later comes back to create a difficulty. The rate of 14.5% is for all patients at UNM. The control group cesarean rate was only 11.5%. The study group rate was 7.5%. This was not significant, based on the number of patients in the study. However, there may be a real difference here but there just
wasn't enough patients to demonstrate it. Why was the control group rate lower than the overall rate for the hospital? Because the study and control group were all low risk patients. If the authors had been able to anticipate this difference when they did their power analysis, they may have been able to show a difference.

As stated in the abstract, the other significant findings were a shorter first stage of labor in study group patients (which lead to a shorter total length of labor in study group patients) and a higher dose of pitocin received by study group patients. There was no difference in the length of the second and third stages of labor in the two groups. The authors then looked at the influence of epidural anesthesia. They found that the difference between the groups in length of labor persisted
whether or not the patient had an epidural. However, while the length of labor was longer in Study group patients with epidurals than in study group patients without epidurals and longer in control patients with epidurals than in control patients without epidurals, we are not told by the authors whether or not this is statistically significant.

Neonatal outcomes evaluated were infant weight, Apgar score <7 at 5 min., NICU admission, and cord pH<7.0. There were no differences in these outcomes between the two groups.

In summation, the authors have shown that patients receiving early amniotomy and oxytocin, if needed, by an aggressive high-dose protocol have shorter labors and do not have an increased incidence of the adverse neonatal outcomes that were evaluated. This is important information to have. They also have data that implies that perhaps this may lower the cesarean rate by as much as 35%, from 11.5% to 7.5%, but their study was not large enough for this to reach statistical significance. I would suggest that these or other authors repeat this evaluation after doing a power study to see how many patients are required to demonstrate this fact with statistical significance.

One of the differences between other studies, this study, and the AML as described by O'Driscoll is the evaluation of the cervix for the diagnosis of labor. This study and the study of Frigoletto3 et al (which showed no decline in the cesarean rate) used 80% effacement as one of their criteria for the diagnosis of labor. O'Driscoll4 says that, in nulliparas, the external cervical os is the part that counts for cervical dilatation and that this cannot happen prior to complete effacement. On the other hand, the study of Turner5 which did show a decrease in the cesarean rate followed the AML standard of 100% effacement. Perhaps this slight difference in the criteria for admission to L & D could make the difference.

Another point of difference is that neither this study nor Frigoletto et al mention anything about a commitment to delivery by 12 hours after admission, O'Driscoll makes a big point that this is a key part of AML. In the stud from Dublin, 98% of all patients are delivered in 12 hours or less after admission. In this study, 75% of those in the study group and 59% of those in the control group delivered in 12 hours or less. Would this actual commitment to delivery by cesarean at 12 hours be
enough to change the management so that fewer would make it to the 12 hours???

One final comment, the questions regarding the "Active Management of Labor" have not yet been answered. However, this study may show some benefit to its use by shortening labor and raises the point that with a large enough number of patients, it may have shown a decrease in the cesarean rate. This lends credence to the performance of another larger study.

References:

  1. O'Driscoll K, Meagher D, & Boylan P. Active management of labor. 3rd ed. Aylesbury:Mosby, 1993.
  2. O'Driscoll K, Jackson R, Gallagher JT. Prevention of prolonged labor. BMJ 1969;2:477-81
  3. Frigoletto FD, Lieberman E, Lang JM, Cohen A, Barss V, Ringer S, & Datta S. A clinical trial of active management of labor. NEJM 1995;333:745-50
  4. O'Driscoll K, Meagher D, & Boylan P. Active management of labor. 3rd ed. P.117 Aylesbury:Mosby, 1993
  5. Turner MJ, Brassil M, & Gordon H. Active management of labor associated with a decrease in the cesarean rate in nulliparas. Obstet & Gynecol 1988;71:150-5


Comments from Dr. Malcolm Griffiths <Malcolm@mgriff22.demon.co.uk>
  1. Given Dan was slightly negative about whether they'd achieved their objective and his implication that the study justified a larger study, I thought that that ought to mean a rating of 4 rather than 5.
  2. It is worth stating that AML is not intended to lower CS rate, but rather to guarantee a limited duration of labour(~labor). Whilst A couple of authors have claimed to show a reduction.
  3. Knowing Mike Turner well (first author of one of the referenced papers) and the unit the work was done in, I would comment that they didn't show that AML lead to a lower CS rate. When AML was strictly adhered to was when there was a chief resident (ie, MT) who was so enthusiastic and present on delivery suite for 16 hours a day, the CS rate plummeted. He was succeeded by less of a zealot (also known to me) and the CS rate went back up. The next guyt was also an AML zealot and it dipped down again. In short the CS rate at NPH Yo-Yo's according to who the senior staff are whilst the AML protocol remains unaltered.
  4. The review (and ? the paper) failed to mention the work of Thornton, Lilford et al, who have used meta-analysis and RCTs to show that the crucial elements of AML are neither amniotomy or syntocinon, but rather continuous support in labour.

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