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Randomized trial of ambulation versus oxytocin for labor enhancement: A preliminary report
Randomized trial of ambulation versus oxytocin for labor enhancement: A preliminary report JOHN FRANK RICHARD
A.
READ,
C.
LIEUTENANT
MILLER,
M.D.
H.
M.D.
PAUL,
MC,
COLONEL,
USA
Los Angeles, Cal{fornia Published reports imply that intrapartum ambulation may improve labor. This suggests the possible efficacy of ambulation in labors requiring augmentation, provided that adequate monitoring surveillance is maintained. Fourteen patients who failed to progress in active-phase labor, and who required augmentation for “inadequate” contractions were randomized into ambulation (eight) and oxytocin (six) groups. Internal fetal monitoring was used in all patients for 30 minute baseline and 2 hour study periods, with two-channel telemetry used in ambulating patients. Oxytocin was administered by infusion pump. Study parameters included changes in cervical dilation and station, contraction frequency, intensity and baseline tonus, and uterine activity. Labor progress was slightly but not significantly better in the ambulatory group. A mean increase in uterine activity units (UAU) in the ambulatory group was immediate to ranges not reached in the oxytocin group for 2 hours. Increase in Montevideo units was slightly greater in the ambulatory group during the first hour, but was exceeded by the oxytocin group during the second hour. These initial observations seem to indicate that, in terms of labor progress and initial effects on uterine activity, ambulation is as effective as oxytocin for the enhancement of labor and warrants further investigation. (AM. J. OBSTET. GYNECOL.
139:669,
1961.)
INTRAPARTUM assumption of the vertical position by the parturient patient is associated with a shortened duration of labor according to published reintenports. I---) In addition to increases in contraction sity’, 4 and total uterine activity,2. 3 a synergistic effect of gravity which adds approximately 30 mm Hg to the
THE
From the Department of Obstetrics and Gynecology, University of Southern Calijornia School of Medicine, and Women’s Hospital, Los Angeles County/University Southern California Medical Center, Los Angeles, California. Receizwd for publication Accepted December
August
of
18, 1980.
1, 1980.
Reprint requests: Dr. Richard H. Paul, Department Obstetrzcs and Gynecology, Women’s Hospital, Los Angeles, California 90033.
oj
Table I. Patient characteristics All (n = 14)
Age W Parity: Nulliparas Multiparas Gestational age (wk)
23.1
Oxytocin
Ambulation
(n = 6)
(n = 8)
21.2
24.6
10
5
5
4 40.7
1
3
40.9
40.5
pressure exerted by the fetal head on the cervix has been demonstrated.3. 4 Our own observations on ambulant patients have shown an increase in the frequency of contractions in the vertical versus the lateral positi0n.j The demonstrated improvement in the efficiency of normal labor suggests the possible efficacy of ambula669
670
Table
Read, Miller, and Paul
II. Labor
progress
characteristics Alllprogress (n = 14)
Dilation (cm) Start End observation End 1 hr End 2 hr
4.41 4.41 5.32 6.35
Station Start End observation End 1 hr End 2 hr
-0.86 -0.86 -0.36 +0.27
2 1.0 2 1.3 r 2*
k 0.8 + 0.7 f l.l*
Oxytocinlprogwss (n
4.37 ” 0.4 4.37 4.92 * 1.2 6.0 2 2.3
0 0.91 1.03
-0.42 -0.42 -0.17 +0.25
0 0.50 0.63
2 0.4 k 0.6 f 1.1
,4 mbulation
=6)
(n
0 0.58 1.08
0 0.25 0.32
4.44 4.44 5.62 6.64
-1.19 -1.19 -0.5 +0.29
lpr0gres.s = 8)
t- 1.3 t ”
0 1.19 1.02
1.4 1.91-
2 1.0
0 0.69 0.79
2 0.8 rt 1.1t
*n = 13. tn = 7.
Table
III. Outcome
characteristics All (n = 14)
Type of delivery: Normal spontaneous Forceps Cesarean section Birth weight (gm) Apgar score: 1 min 5 min
vaginal
6 5 3 3,815
k 279 6.9 8.7
tion in labor that requires augmentation, provided that adequate monitoring surveillance is maintained. Furthermore, the availability of internal two-channel telemetric fetal monitoring, the lack of any demonstrable ill effects with ambulation in labor in properly selected patients, and improved tolerance to pain and comfort with ambulation versus increased pain with oxytocin, also suggest ambulation for enhancement of labor as a viable and possibly equivalent alternative to oxytocin in selected patients.
Patients and methods To date, 14 patients in active labor at the Los Angeles County/University of Southern California Medical Center who demonstrated failure to progress over one or more hours, and whose contractions were deemed to be inadequate and to require augmentation, were selected for the study. The patients were prospectively randomized into either the oxytocin group (six) or the ambulation group (eight). All patients had ruptured membranes and their fetuses were monitored internally by means of a spiral scalp. electrode and transcervital intrauterine catheter connected either directly or via two-channel telemetry (Corometrics) to a Model 1 12 Corometrics fetal monitor. The level of the strain gauge was at the miduterus and to the right lateral side
Oxytocin (n = 6)
2 2 2 3,830
2 129
6.5 (3-9) 8.7 (7-10)
Am&ulation (n = 8)
4 3 1 3,804
2 364
7.3 (3-9)
8.8 (8-9)
at the level of the umbilicus, intersecting a line from the xyphoid to the symphysis. In addition to uterine activity and fetal heart rate (FHR), on-line quantitation of uterine activity units and heart rate variability (Varidex) were recorded. Uterine activity units (UAU) were quantitated for each lo-minute interval (UAU in mm Hg per minute = area under uterine contractions trace above zero). After an initial pelvic examination, a 30 minute baseline observation was conducted with the patient in the right or left lateral recumbent position. The above-noted parameters were recorded and a second pelvic examination followed this 30 minute period. The study period of 2 hours, divided into 1 hour segments followed by pelvic examination, was then begun. Patients receiving oxytocin were started on an intravenous infusion, via Harvard pump, at 0.2 to 0.4 mU/min. The infusion was increased at 15 minute intervals until contractions occurred every 2 to 3 minutes and achieved an amplitude of over 50 mm Hg. Ambulatory patients remained out of bed, walking, standing, or, occasionally, sitting, except during pelvic examination. All patients received intravenous fluids but no analgesics or anesthesia during the study period. The study was terminated because of imminent delivery in one patient and fatigue in two patients in
Ambulation
the ambulatory group. The subsequent course of labor and outcome statistics were tabulated, and statistical analysis by Student’s t test, chi square, or MannWhitney U test, where appropriate, were carried out.
oxytocin
for labor
enhancement
671
AMBULATION VS OXYTOCH FOR AUGMENTATION 160 AMBULATION
140
c 1
Results Basic characteristics of the patients are present in Table I. No significant differences existed in age or gestational age. The characteristics of labor progress are listed in Table II. In addition to no progress of active-phase labor for at least I hour prior to the study, no patient made any progress during the 30 minute observation period in either descent or dilation. During the first study hour, all eight ambulatory patients made progress in both descent and dilation, whereas only three of the six oxytocin patients made progress. Two patients in the ambulation group dropped out because of “fatigue,” one at the end of the first hour and a second at 11% hours. One patient underwent delivery after 1% hours of the study period. During the second hour, four of the six oxytocin patients and seven of seven ambulatory patients made progress. Neither the mean dilation change of 2.2 cm (ambulatory) versus 1.63 cm (oxytocin) nor the mean station change of + 1.48 cm (ambulatory) versus +0.67 cm (oxytocin) was significantly different over 2 hours. A comparison of the change in uterine activity with mean baseline uterine activity in terms of both LJAU and Montevideo units is presented in Fig. 1. There was significant increase in UAU during the first hour in the ambulatory group, whereas the difference during the second hour was not significant. In terms of Montevideo units, there were no significant differences in the two groups except in the eighth and twelfth 10 minute study intervals, during which the oxytocin group was better (Mann: p < 0.04 and p < 0.01, respectively). The frequency of contractions increased in seven of eight ambulatory and four of six oxytocintreated patients during the first hour compared to baseline observations. The baseline tone in the ambulatory group averaged 10 mm Hg in the supine position, 6.5 mm Hg in the lateral position, and 18.75 mm Hg in the upright position. The mean contraction amplitude in the ambulatory group increased from 4 1 mm Hg during observation to 53.75 mm Hg with ambulation. The 12.25 mm Hg mean increase in tone from the lateral recumbent to vertical ambulatory position was similar to the 12.75 mm Hg mean increase in contraction amplitude. Corrected for increase in tone, contraction amplitude increased in four of eight patients and decreased in four of eight.
versus
120
-
100
-
OXYTOCIN
H
N= 8
-
N= 6
PELVIC “A.
* /
p
Y
$ 80 2 5
60 -
i? 2 40 IL
-1
-
-f -f -‘
- I .
l
l
t
1
BASELINE
1
I
I
I
I,
2 3 4 5 TEN MINUTE
I1
I
,
6 7 6 9 1011 INTERVAL
1
I
12
Fig. 1. Mean changes in uterine activity during the study period versus mean baseline values in oxytocin-stimulated and ambulated patients.
Outcome statistics are presented in Table III. No significant differences were observed in this small number of patients. Noteworthy is the fact that six of eight ambulatory patients required further augmentation with oxytocin after the study. In terms of subjective evaluation of pain, all patients who received oxytocin complained of increased pain, whereas four patients in the ambulatory group felt less pain and three said that the pain remained the same. The single patient who experienced increased discomfort had the greatest increase in contraction amplitude (corrected for tone), but otherwise changes in the perception of pain did not correlate with changes in amplitude. No significant changes in either FHR baseline variability or patterns were observed with ambulation.
Comment Some variation of the vertical position for labor and delivery was traditional until “modern” medical intervention in the last two centuries. Only recently has interest been renewed in this manner of intrapartum conduct. From the limited number of studies, with small numbers of patients, two facts are readily apparent with the use of vertical position: (1) patients are
672
Read,
Miller,
and Paul
more comfortable, and (2) labors tend to be shorter. An accumulating experience seems to indicate that the assumption of the vertical position in labor is safe fol mothers and fetuses,“+” provided that certain conditions are met. These include: (1) fetal head well applied to the cervix, (2) no evidence of f’etal distress (FHR baseline tracing), and (S) a nonmedicated, nonexbausted, and well-motivated patient. Finally, the potential efficacy of ambulation for augmentation is suggested by the more quantitative observations made on labor in the vertical position.“. ’ Previous study of intrapartum ambulation has dealt with “normal” labors. Although other parameters were normal in the patients in the present study, the labors were abnormal. being characterized by failure to progress and “inadequate” uterine activity. This clinical diagnosis was confirmed during a suitable observation period with the patient in the lateral position prior to the study. Ambulation produced an imtnediate increase in frequency and amplitude of contractions, and in baseline tonus. This was most apparent in the effect on UAU (Fig. l), where the mean levels of UAU in the ambulatory group were not reached by the oxytocin 2 hours. However, if contracgroup for approximately tion amplitude was corrected for increased tonus, the absolute intensity of contractions was not higher than in the lateral position. The increase observed, therefore, in Montevideo units (intensity [i.e., amplitude tonus] x frequency/ 10 min) must have been due mainly to increased frequency of contractions observed in the vertical versus the lateral position. The gradual increase in both UAU and Montevideo units in the oxytocin group was due to a gradual increase in both frequency and intensity seen with increasing doses of oxytocin. One must ask which of the two quantitations of uterine activity is most reflective in this situation. Can changes in “tonus” be discounted? Mendez-Bauer and
REFERENCES
1. Mitre, I. N.: The influence of maternal position on duration of the active phase of labor, Int. -I. Gynaecol. Obstet. 12:181,
1974.
.
2. Mendez-Bauer, C., Arroyo, I., Garcia Ramos, C., et al.: Effects of standing position on spontaneous uterine contractility and other aspects of labor. J. Perinat. Med. 3:!9, 1979. 3. Caldeyro-Barcia, R.: The influence of maternal position on fine spontaneous rupture of the membranes. Progress of labor and fetal head compression, Birth Fam. J. 6:7, 1979. 4. Mendez-Bauer, C., Arroyo, J., Mendez, A., et al.: Effects of different maternal positions during labor. in Roth, G., and
associates4 used an extraovular balloon between the head and cervix to document a YO+ mm Hg inc-rrasc in pressure on the cervix in vertical position. The! state. but do not document, that this pressure is not transnlitted to the intrauterine cavity. The increase in ititrauterine baseline tonus obset-ved in our patients ma) have been an artifact. although we attempted to minimize this by placement of the transducer relative to the estimated catheter tip (mlduterus = umbilicus). On the other hand, part of the illcreased pressul-r that Mender-Bauer and associates f’orrnd on the cervix ma! have been due to pressure from intra-abciorninal and thoracic contents and, thus, ha\ e been reHec-ted in intrauterine tonus. ‘The vector of gravity (weight of intrauterine contents) may have accounted for the rest of’ the change in cervical pressure. In eithei- (‘abe. if Mender-Bauer and associates’ tracing’ is examined, the increase in amplitude seems also LO be due to this increase in “torus.” Lt is probable this “tonus” or change in cervical pressure which is responsible for the increased efficacy of labor in the vertical positioll. Even though both the immediate effect of smbulation and the enhanced tolerance to pain would seem to recommend it over oxytocin, maternal fatigue and motivation also appear to be limiting factors. The patients in the present study. because ot. stud\ design, were not allowed to rest at will. The 11s~’of sitting’ and the alternation of vertical and recumbent positions’ have both been shown to be associated wit11 shortened labors, and perhaps would enable more extensive use of ambulation in these patients with earl) active-phase arrests. Finally, although both the rates of labor progress and outcome in these two groups are quite similar, the numbers are small, so that further study, perhaps wit01 some design modifications, will be needed to truly demonstrate either equivalency or the superioritv of one of these methods of labor enhancement.
Bratleby, L. A., editors: Fifth European Congress of Perinatal Medicine, Uppsala, Sweden, 1976. Stockholm, 1976, Almqvist and Wiksell International, p. 233. 5. Read, J. A., Miller, F. C., and Paul, R. H.: Ambulation in labor: Maternal and fetal effects, Scientific Exhibit, Ameriand Gynecologistscan College of Obstetricians American College of Medicine, New Orleans. Louisiana. May 5-8, 1980. 6. Flynn, A., and Kelly, J.: Continuous fetal monitoring in the ambulant patient in labor, in Roth, G.. and Bratleby, L. A., editors: Fifth European Congress of’ Perinatal Medicine, Uppsala, Sweden, 1976. Stockholm, 1976, Almqvist and Wiksell International, p. 238.
A.
READ,
C.
LIEUTENANT
MILLER,
M.D.
H.
M.D.
PAUL,
MC,
COLONEL,
USA
Los Angeles, Cal{fornia Published reports imply that intrapartum ambulation may improve labor. This suggests the possible efficacy of ambulation in labors requiring augmentation, provided that adequate monitoring surveillance is maintained. Fourteen patients who failed to progress in active-phase labor, and who required augmentation for “inadequate” contractions were randomized into ambulation (eight) and oxytocin (six) groups. Internal fetal monitoring was used in all patients for 30 minute baseline and 2 hour study periods, with two-channel telemetry used in ambulating patients. Oxytocin was administered by infusion pump. Study parameters included changes in cervical dilation and station, contraction frequency, intensity and baseline tonus, and uterine activity. Labor progress was slightly but not significantly better in the ambulatory group. A mean increase in uterine activity units (UAU) in the ambulatory group was immediate to ranges not reached in the oxytocin group for 2 hours. Increase in Montevideo units was slightly greater in the ambulatory group during the first hour, but was exceeded by the oxytocin group during the second hour. These initial observations seem to indicate that, in terms of labor progress and initial effects on uterine activity, ambulation is as effective as oxytocin for the enhancement of labor and warrants further investigation. (AM. J. OBSTET. GYNECOL.
139:669,
1961.)
INTRAPARTUM assumption of the vertical position by the parturient patient is associated with a shortened duration of labor according to published reintenports. I---) In addition to increases in contraction sity’, 4 and total uterine activity,2. 3 a synergistic effect of gravity which adds approximately 30 mm Hg to the
THE
From the Department of Obstetrics and Gynecology, University of Southern Calijornia School of Medicine, and Women’s Hospital, Los Angeles County/University Southern California Medical Center, Los Angeles, California. Receizwd for publication Accepted December
August
of
18, 1980.
1, 1980.
Reprint requests: Dr. Richard H. Paul, Department Obstetrzcs and Gynecology, Women’s Hospital, Los Angeles, California 90033.
oj
Table I. Patient characteristics All (n = 14)
Age W Parity: Nulliparas Multiparas Gestational age (wk)
23.1
Oxytocin
Ambulation
(n = 6)
(n = 8)
21.2
24.6
10
5
5
4 40.7
1
3
40.9
40.5
pressure exerted by the fetal head on the cervix has been demonstrated.3. 4 Our own observations on ambulant patients have shown an increase in the frequency of contractions in the vertical versus the lateral positi0n.j The demonstrated improvement in the efficiency of normal labor suggests the possible efficacy of ambula669
670
Table
Read, Miller, and Paul
II. Labor
progress
characteristics Alllprogress (n = 14)
Dilation (cm) Start End observation End 1 hr End 2 hr
4.41 4.41 5.32 6.35
Station Start End observation End 1 hr End 2 hr
-0.86 -0.86 -0.36 +0.27
2 1.0 2 1.3 r 2*
k 0.8 + 0.7 f l.l*
Oxytocinlprogwss (n
4.37 ” 0.4 4.37 4.92 * 1.2 6.0 2 2.3
0 0.91 1.03
-0.42 -0.42 -0.17 +0.25
0 0.50 0.63
2 0.4 k 0.6 f 1.1
,4 mbulation
=6)
(n
0 0.58 1.08
0 0.25 0.32
4.44 4.44 5.62 6.64
-1.19 -1.19 -0.5 +0.29
lpr0gres.s = 8)
t- 1.3 t ”
0 1.19 1.02
1.4 1.91-
2 1.0
0 0.69 0.79
2 0.8 rt 1.1t
*n = 13. tn = 7.
Table
III. Outcome
characteristics All (n = 14)
Type of delivery: Normal spontaneous Forceps Cesarean section Birth weight (gm) Apgar score: 1 min 5 min
vaginal
6 5 3 3,815
k 279 6.9 8.7
tion in labor that requires augmentation, provided that adequate monitoring surveillance is maintained. Furthermore, the availability of internal two-channel telemetric fetal monitoring, the lack of any demonstrable ill effects with ambulation in labor in properly selected patients, and improved tolerance to pain and comfort with ambulation versus increased pain with oxytocin, also suggest ambulation for enhancement of labor as a viable and possibly equivalent alternative to oxytocin in selected patients.
Patients and methods To date, 14 patients in active labor at the Los Angeles County/University of Southern California Medical Center who demonstrated failure to progress over one or more hours, and whose contractions were deemed to be inadequate and to require augmentation, were selected for the study. The patients were prospectively randomized into either the oxytocin group (six) or the ambulation group (eight). All patients had ruptured membranes and their fetuses were monitored internally by means of a spiral scalp. electrode and transcervital intrauterine catheter connected either directly or via two-channel telemetry (Corometrics) to a Model 1 12 Corometrics fetal monitor. The level of the strain gauge was at the miduterus and to the right lateral side
Oxytocin (n = 6)
2 2 2 3,830
2 129
6.5 (3-9) 8.7 (7-10)
Am&ulation (n = 8)
4 3 1 3,804
2 364
7.3 (3-9)
8.8 (8-9)
at the level of the umbilicus, intersecting a line from the xyphoid to the symphysis. In addition to uterine activity and fetal heart rate (FHR), on-line quantitation of uterine activity units and heart rate variability (Varidex) were recorded. Uterine activity units (UAU) were quantitated for each lo-minute interval (UAU in mm Hg per minute = area under uterine contractions trace above zero). After an initial pelvic examination, a 30 minute baseline observation was conducted with the patient in the right or left lateral recumbent position. The above-noted parameters were recorded and a second pelvic examination followed this 30 minute period. The study period of 2 hours, divided into 1 hour segments followed by pelvic examination, was then begun. Patients receiving oxytocin were started on an intravenous infusion, via Harvard pump, at 0.2 to 0.4 mU/min. The infusion was increased at 15 minute intervals until contractions occurred every 2 to 3 minutes and achieved an amplitude of over 50 mm Hg. Ambulatory patients remained out of bed, walking, standing, or, occasionally, sitting, except during pelvic examination. All patients received intravenous fluids but no analgesics or anesthesia during the study period. The study was terminated because of imminent delivery in one patient and fatigue in two patients in
Ambulation
the ambulatory group. The subsequent course of labor and outcome statistics were tabulated, and statistical analysis by Student’s t test, chi square, or MannWhitney U test, where appropriate, were carried out.
oxytocin
for labor
enhancement
671
AMBULATION VS OXYTOCH FOR AUGMENTATION 160 AMBULATION
140
c 1
Results Basic characteristics of the patients are present in Table I. No significant differences existed in age or gestational age. The characteristics of labor progress are listed in Table II. In addition to no progress of active-phase labor for at least I hour prior to the study, no patient made any progress during the 30 minute observation period in either descent or dilation. During the first study hour, all eight ambulatory patients made progress in both descent and dilation, whereas only three of the six oxytocin patients made progress. Two patients in the ambulation group dropped out because of “fatigue,” one at the end of the first hour and a second at 11% hours. One patient underwent delivery after 1% hours of the study period. During the second hour, four of the six oxytocin patients and seven of seven ambulatory patients made progress. Neither the mean dilation change of 2.2 cm (ambulatory) versus 1.63 cm (oxytocin) nor the mean station change of + 1.48 cm (ambulatory) versus +0.67 cm (oxytocin) was significantly different over 2 hours. A comparison of the change in uterine activity with mean baseline uterine activity in terms of both LJAU and Montevideo units is presented in Fig. 1. There was significant increase in UAU during the first hour in the ambulatory group, whereas the difference during the second hour was not significant. In terms of Montevideo units, there were no significant differences in the two groups except in the eighth and twelfth 10 minute study intervals, during which the oxytocin group was better (Mann: p < 0.04 and p < 0.01, respectively). The frequency of contractions increased in seven of eight ambulatory and four of six oxytocintreated patients during the first hour compared to baseline observations. The baseline tone in the ambulatory group averaged 10 mm Hg in the supine position, 6.5 mm Hg in the lateral position, and 18.75 mm Hg in the upright position. The mean contraction amplitude in the ambulatory group increased from 4 1 mm Hg during observation to 53.75 mm Hg with ambulation. The 12.25 mm Hg mean increase in tone from the lateral recumbent to vertical ambulatory position was similar to the 12.75 mm Hg mean increase in contraction amplitude. Corrected for increase in tone, contraction amplitude increased in four of eight patients and decreased in four of eight.
versus
120
-
100
-
OXYTOCIN
H
N= 8
-
N= 6
PELVIC “A.
* /
p
Y
$ 80 2 5
60 -
i? 2 40 IL
-1
-
-f -f -‘
- I .
l
l
t
1
BASELINE
1
I
I
I
I,
2 3 4 5 TEN MINUTE
I1
I
,
6 7 6 9 1011 INTERVAL
1
I
12
Fig. 1. Mean changes in uterine activity during the study period versus mean baseline values in oxytocin-stimulated and ambulated patients.
Outcome statistics are presented in Table III. No significant differences were observed in this small number of patients. Noteworthy is the fact that six of eight ambulatory patients required further augmentation with oxytocin after the study. In terms of subjective evaluation of pain, all patients who received oxytocin complained of increased pain, whereas four patients in the ambulatory group felt less pain and three said that the pain remained the same. The single patient who experienced increased discomfort had the greatest increase in contraction amplitude (corrected for tone), but otherwise changes in the perception of pain did not correlate with changes in amplitude. No significant changes in either FHR baseline variability or patterns were observed with ambulation.
Comment Some variation of the vertical position for labor and delivery was traditional until “modern” medical intervention in the last two centuries. Only recently has interest been renewed in this manner of intrapartum conduct. From the limited number of studies, with small numbers of patients, two facts are readily apparent with the use of vertical position: (1) patients are
672
Read,
Miller,
and Paul
more comfortable, and (2) labors tend to be shorter. An accumulating experience seems to indicate that the assumption of the vertical position in labor is safe fol mothers and fetuses,“+” provided that certain conditions are met. These include: (1) fetal head well applied to the cervix, (2) no evidence of f’etal distress (FHR baseline tracing), and (S) a nonmedicated, nonexbausted, and well-motivated patient. Finally, the potential efficacy of ambulation for augmentation is suggested by the more quantitative observations made on labor in the vertical position.“. ’ Previous study of intrapartum ambulation has dealt with “normal” labors. Although other parameters were normal in the patients in the present study, the labors were abnormal. being characterized by failure to progress and “inadequate” uterine activity. This clinical diagnosis was confirmed during a suitable observation period with the patient in the lateral position prior to the study. Ambulation produced an imtnediate increase in frequency and amplitude of contractions, and in baseline tonus. This was most apparent in the effect on UAU (Fig. l), where the mean levels of UAU in the ambulatory group were not reached by the oxytocin 2 hours. However, if contracgroup for approximately tion amplitude was corrected for increased tonus, the absolute intensity of contractions was not higher than in the lateral position. The increase observed, therefore, in Montevideo units (intensity [i.e., amplitude tonus] x frequency/ 10 min) must have been due mainly to increased frequency of contractions observed in the vertical versus the lateral position. The gradual increase in both UAU and Montevideo units in the oxytocin group was due to a gradual increase in both frequency and intensity seen with increasing doses of oxytocin. One must ask which of the two quantitations of uterine activity is most reflective in this situation. Can changes in “tonus” be discounted? Mendez-Bauer and
REFERENCES
1. Mitre, I. N.: The influence of maternal position on duration of the active phase of labor, Int. -I. Gynaecol. Obstet. 12:181,
1974.
.
2. Mendez-Bauer, C., Arroyo, I., Garcia Ramos, C., et al.: Effects of standing position on spontaneous uterine contractility and other aspects of labor. J. Perinat. Med. 3:!9, 1979. 3. Caldeyro-Barcia, R.: The influence of maternal position on fine spontaneous rupture of the membranes. Progress of labor and fetal head compression, Birth Fam. J. 6:7, 1979. 4. Mendez-Bauer, C., Arroyo, J., Mendez, A., et al.: Effects of different maternal positions during labor. in Roth, G., and
associates4 used an extraovular balloon between the head and cervix to document a YO+ mm Hg inc-rrasc in pressure on the cervix in vertical position. The! state. but do not document, that this pressure is not transnlitted to the intrauterine cavity. The increase in ititrauterine baseline tonus obset-ved in our patients ma) have been an artifact. although we attempted to minimize this by placement of the transducer relative to the estimated catheter tip (mlduterus = umbilicus). On the other hand, part of the illcreased pressul-r that Mender-Bauer and associates f’orrnd on the cervix ma! have been due to pressure from intra-abciorninal and thoracic contents and, thus, ha\ e been reHec-ted in intrauterine tonus. ‘The vector of gravity (weight of intrauterine contents) may have accounted for the rest of’ the change in cervical pressure. In eithei- (‘abe. if Mender-Bauer and associates’ tracing’ is examined, the increase in amplitude seems also LO be due to this increase in “torus.” Lt is probable this “tonus” or change in cervical pressure which is responsible for the increased efficacy of labor in the vertical positioll. Even though both the immediate effect of smbulation and the enhanced tolerance to pain would seem to recommend it over oxytocin, maternal fatigue and motivation also appear to be limiting factors. The patients in the present study. because ot. stud\ design, were not allowed to rest at will. The 11s~’of sitting’ and the alternation of vertical and recumbent positions’ have both been shown to be associated wit11 shortened labors, and perhaps would enable more extensive use of ambulation in these patients with earl) active-phase arrests. Finally, although both the rates of labor progress and outcome in these two groups are quite similar, the numbers are small, so that further study, perhaps wit01 some design modifications, will be needed to truly demonstrate either equivalency or the superioritv of one of these methods of labor enhancement.
Bratleby, L. A., editors: Fifth European Congress of Perinatal Medicine, Uppsala, Sweden, 1976. Stockholm, 1976, Almqvist and Wiksell International, p. 233. 5. Read, J. A., Miller, F. C., and Paul, R. H.: Ambulation in labor: Maternal and fetal effects, Scientific Exhibit, Ameriand Gynecologistscan College of Obstetricians American College of Medicine, New Orleans. Louisiana. May 5-8, 1980. 6. Flynn, A., and Kelly, J.: Continuous fetal monitoring in the ambulant patient in labor, in Roth, G.. and Bratleby, L. A., editors: Fifth European Congress of’ Perinatal Medicine, Uppsala, Sweden, 1976. Stockholm, 1976, Almqvist and Wiksell International, p. 238.