AMERICAN JOURNALOF PERINATOLOGYNOLUME 7, NUMBER 4
October 1990
EFFECT OF ACTIVE MANAGEMENT ON LATENT PHASE LABOR Peter C. Boylan, M.B., M.R.C. O.G., and Valerie M . Parisi, M.D., M.P.H.
The effect of active management on latent phase labor was assessed in 197 consecutive nulliparous women. Active management resulted in a significant shortening of the latent phase but had no effect on active phase labor. Patients undergoing induction of labor had latent phases that were almost identical to the accepted norm. The effect of active management may be due to early diagnosis of labor and early intervention in the form of artificial rupture of membranes and selective high-dose oxytocin infusion.
In contemporary practice, first-stage labor is divided into latent and active phases. Latent phase labor is defined as the period of time from the onset of labor until the cervix is 3 cm dilated and may last up to 20 hours in nulliparas.1 There may be a reluctance among clinicians to accept a firm diagnosis of labor until the cervix is 3 cm dilated, and, subsequently, management may be characterized by a "hands-off' approach, with most authorities advocating watchful expectancy or sedation. In contrast, a firm diagnosis of labor is accepted much earlier with active management (AML),an approach to the management of labor in nulliparas developed over the past 25 years by O'Driscoll and colleagues.2-4 With AML, diagnosis of labor is accepted in the presence of uterine contractions and cervical effacement, even if the cervix if only 1cm dilated. Once the diagnosis of labor is made, artificial rupture of membranes (ARM)is routine and oxytocin augmentation of labor is begun if the cervix does not dilate at a rate of at least 1 cm per hour. ARM or oxytocin augmentation is not routinely advised in contemporary North American practice until the cervix is at least 3 cm dilated. O'Driscoll and colleagues have consistently reported a short total duration of labor in nulliparas and have attributed this to AML.2-4 Introduction of AML at our institution provided an opportunity to observe the effect of AML on latent phase labor, the time of greatest difference in approach between contemporary management in North America and AML. In this report the effect of AML on latent phase labor in nulliparas is analyzed.
METHODS
The effect of AML on latent phase labor was examined in 19'7 consecutive nulliparous women admitted in spontaneous labor and undergoing vaginal delivery. All patients were managed according to the principles of AML as follows: labor was diagnosed if there were regular uterine contractions, occurring at least every 8 minutes, and the cervix was at least 80% effaced. A history of a bloody show was considered strong supportive evidence. Complete effacement of the cervix was equated with 1 cm dilation. Following diagnosis of labor, amniotic fluid was released by artificial rupture of membranes within 2 hours of admission. Progress in labor was plotted on a graph (Fig. 1).Progress was assessed every 2 hours by sterile vaginal examination. If the cervix did not dilate at a rate of at least 1 cm per hour, oxytocin was administered. Oxytocin was infused at a starting dose of 4 mU/min and increased, by 4mU/min, every 15 minutes to a maximum of 36 mU/min. The rate was not increased if there were more than seven contractions in the preceding 15 minutes. Evidence of fetal distress was a contraindication to infusion of oxytocin. Electronic fetal heart rate monitoring was performed in all cases where oxytocin was infused. Intrauterine pressure catheters were not utilized in this study. Patients were divided into two groups according to cervical dilation on admission: Group A: cervix more than 3 cm (n = 58); group B: cervix less than 3 cm (n = 139). Patients in group A were regarded as being in active phase labor, and those in group B were regarded as being in latent phase labor.
Department of Obstetrics, Gynecology and Reproductive Sciences, Division of Maternal Fetal Medicine, University of Texas Medical School at Houston, Houston, Texas Reprint requests: Dr. Boylan, National Maternity Hospital, Holles Street, Dublin 2, Ireland Copyright O 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: University of British Columbia. Copyrighted material.
ABSTRACT
AMERICAN JOURNAL O F PERINATOLOGYNOLUME 7, NUMBER 4
October 1990
PRlMlGRAVlD LABOR RECORD HERMANN HOSPITAL
Date Name AMlPM
Time of Admission Pains
Yes
No
Show
Yes
No
Ruptured Membranes
Yes
n No
DELIVERED
FULL = 10 cm
9 cm
8 cm
7 cm
6 cm
Downloaded by: University of British Columbia. Copyrighted material.
5 cm 4 cm
3 cm
2 cm
1 cm
UNEFFACED HOURS AFTER ADMISSION
AMNIOTIC FLUID
OXYTOClN
ANALGESIA
-
t
Time of Delivery Duration
Figure 1.
AMIPM Method
S~gnature MO
Labor graph as used in active management of labor.
Nulliparous patients undergoing induction of labor for all indications during the same time period were considered for a third, separate, group C (n = 47). The course of labor in these three groups was then compared with the traditional labor curve of Friedman1 (Fig. 2).
Patients admitted to latent phase labor (group B) had no significant difference in duration of active phase labor (5.3 + 2.9 hours) when compared with those admitted in active phase labor (group a) (4.9 2 3.7 hours) or those in whom labor was induced (group C) (5.5 + 3.5 hours) (Fig. 2). Latent phase labor in group B was significantly shorter (3.1 -C 4.3 hours) (P
October 1990
EFFECT OF ACTIVE MANAGEMENT ON LATENT PHASE LABOR Peter C. Boylan, M.B., M.R.C. O.G., and Valerie M . Parisi, M.D., M.P.H.
The effect of active management on latent phase labor was assessed in 197 consecutive nulliparous women. Active management resulted in a significant shortening of the latent phase but had no effect on active phase labor. Patients undergoing induction of labor had latent phases that were almost identical to the accepted norm. The effect of active management may be due to early diagnosis of labor and early intervention in the form of artificial rupture of membranes and selective high-dose oxytocin infusion.
In contemporary practice, first-stage labor is divided into latent and active phases. Latent phase labor is defined as the period of time from the onset of labor until the cervix is 3 cm dilated and may last up to 20 hours in nulliparas.1 There may be a reluctance among clinicians to accept a firm diagnosis of labor until the cervix is 3 cm dilated, and, subsequently, management may be characterized by a "hands-off' approach, with most authorities advocating watchful expectancy or sedation. In contrast, a firm diagnosis of labor is accepted much earlier with active management (AML),an approach to the management of labor in nulliparas developed over the past 25 years by O'Driscoll and colleagues.2-4 With AML, diagnosis of labor is accepted in the presence of uterine contractions and cervical effacement, even if the cervix if only 1cm dilated. Once the diagnosis of labor is made, artificial rupture of membranes (ARM)is routine and oxytocin augmentation of labor is begun if the cervix does not dilate at a rate of at least 1 cm per hour. ARM or oxytocin augmentation is not routinely advised in contemporary North American practice until the cervix is at least 3 cm dilated. O'Driscoll and colleagues have consistently reported a short total duration of labor in nulliparas and have attributed this to AML.2-4 Introduction of AML at our institution provided an opportunity to observe the effect of AML on latent phase labor, the time of greatest difference in approach between contemporary management in North America and AML. In this report the effect of AML on latent phase labor in nulliparas is analyzed.
METHODS
The effect of AML on latent phase labor was examined in 19'7 consecutive nulliparous women admitted in spontaneous labor and undergoing vaginal delivery. All patients were managed according to the principles of AML as follows: labor was diagnosed if there were regular uterine contractions, occurring at least every 8 minutes, and the cervix was at least 80% effaced. A history of a bloody show was considered strong supportive evidence. Complete effacement of the cervix was equated with 1 cm dilation. Following diagnosis of labor, amniotic fluid was released by artificial rupture of membranes within 2 hours of admission. Progress in labor was plotted on a graph (Fig. 1).Progress was assessed every 2 hours by sterile vaginal examination. If the cervix did not dilate at a rate of at least 1 cm per hour, oxytocin was administered. Oxytocin was infused at a starting dose of 4 mU/min and increased, by 4mU/min, every 15 minutes to a maximum of 36 mU/min. The rate was not increased if there were more than seven contractions in the preceding 15 minutes. Evidence of fetal distress was a contraindication to infusion of oxytocin. Electronic fetal heart rate monitoring was performed in all cases where oxytocin was infused. Intrauterine pressure catheters were not utilized in this study. Patients were divided into two groups according to cervical dilation on admission: Group A: cervix more than 3 cm (n = 58); group B: cervix less than 3 cm (n = 139). Patients in group A were regarded as being in active phase labor, and those in group B were regarded as being in latent phase labor.
Department of Obstetrics, Gynecology and Reproductive Sciences, Division of Maternal Fetal Medicine, University of Texas Medical School at Houston, Houston, Texas Reprint requests: Dr. Boylan, National Maternity Hospital, Holles Street, Dublin 2, Ireland Copyright O 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: University of British Columbia. Copyrighted material.
ABSTRACT
AMERICAN JOURNAL O F PERINATOLOGYNOLUME 7, NUMBER 4
October 1990
PRlMlGRAVlD LABOR RECORD HERMANN HOSPITAL
Date Name AMlPM
Time of Admission Pains
Yes
No
Show
Yes
No
Ruptured Membranes
Yes
n No
DELIVERED
FULL = 10 cm
9 cm
8 cm
7 cm
6 cm
Downloaded by: University of British Columbia. Copyrighted material.
5 cm 4 cm
3 cm
2 cm
1 cm
UNEFFACED HOURS AFTER ADMISSION
AMNIOTIC FLUID
OXYTOClN
ANALGESIA
-
t
Time of Delivery Duration
Figure 1.
AMIPM Method
S~gnature MO
Labor graph as used in active management of labor.
Nulliparous patients undergoing induction of labor for all indications during the same time period were considered for a third, separate, group C (n = 47). The course of labor in these three groups was then compared with the traditional labor curve of Friedman1 (Fig. 2).
Patients admitted to latent phase labor (group B) had no significant difference in duration of active phase labor (5.3 + 2.9 hours) when compared with those admitted in active phase labor (group a) (4.9 2 3.7 hours) or those in whom labor was induced (group C) (5.5 + 3.5 hours) (Fig. 2). Latent phase labor in group B was significantly shorter (3.1 -C 4.3 hours) (P
