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Breast stimulation test and oxytocin challenge test in fetal surveillance: A prospective randomized study
Breast stimulation test and oxytocin challenge test in fetal surveillance: A prospective randomized study Shlomo Lipitz, M.D., Gad Barkai, M.D., Jaron Rabinovici, M.D., and Shlomo Mashiach, M.D. Tel Hashomer, Israel Fifty heatlhy gravidas with uncomplicated singleton pregnancies at a gestational age of 35 to 42 weeks were assigned at random for the performance of either a breast stimulation test or an oxytocin challenge test after a nonreactive nonstress test. A satisfactory contraction stress test was achieved in 21 of 25 women in the breast stimulation test group and in 24 of 25 women in the oxytocin challenge test group (nonsignificant difference). Significant differences were found in the cumulative rate of achieved contraction stress tests: in the breast stimulation test group 17 of 21 after 20 minutes and 21 of 21 at 50 minutes whereas in the oxytocin challenge test group only four of 24 at 20 minutes, eight of 24 at 50 minutes, and 21 of 24 at 150 minutes. The mean duration for the achievement of a contraction stress test was 20.9 ± 11.5 minutes for the breast stimulation test group and 81.3 ± 48.4 minutes in the oxytocin challenge test group. Uterine hyperstimulation occurred once in each group. No gravida went into labor within 24 hours. Breast stimulation test is a satisfactory alternative to the oxytocin challenge test, is less time-consuming, and is simpler to perform. (AM J OssrET GYNECOL 1987;157:1178-81.)
Key words: Fetal monitoring, oxytocin challenge test, breast stimulation test
The contraction stress test and the nonstress test are well-established diagnostic tools for the prenatal evaluation of the fetoplacental unit. 1-3 For practical reasons the nonstress test has been used in most centers as the first diagnostic test followed by a contraction stress test if a nonreactive pattern was obtained. 1 · 5 A contraction stress test is usually performed with either spontaneous uterine contractions or after induction of uterine activity by exogenous oxytocin infusion (oxytocin challenge test). 6 Recently several studies have indicated the efficacy of nipple stimulation for the initiation of uterine contractions, suggesting that the breast stimulation test is a convenient method of performing a contraction stress test. 7 - 10 The breast stimulation test, however, has been associated with a high incidence of uterine hyperstimulation.1I. 12 The purpose of this study was to compare prospectively the use of intravenously administered oxytocin to nipple stimulation for the induction of uterine activity in the performance of a contraction stress test.
Material and methods During the study period nonstress tests were performed on every gravida at a gestational age of 35 to From the Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, and the Sackler School of Medicine. Received for publication November 13, 1986; revised May 5, 1987; accepted june 18, 1987. Reprint requests: Shlomo Lipitz, M.D., Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, 52621 Israel.
1178
42 weeks either as a routine screening procedure at term or after the perception of decreased fetal movements. Subjects with multiple pregnancies, diabetes, hypertension, intrauterine growth retardation, or a pathologic nonstress test (defined as any type of deceleration) were-excluded from this study. Of the 210 subjects fulfilling these criteria, a nonreactive nonstress test was present in 50 patients. A reactive pattern was defined as two fetal heart rate accelerations in any 20minute period, with each acceleration rising at least 15 bpm above baseline and lasting for at least 15 seconds. The 50 patients with a nonreactive nonstress test underwent contraction stress tests. The participants were randomly divided; 25 underwent an oxytocin challenge test and the other 25 women had a breast stimulation test. All testing was performed with the patient in the left lateral recumbent position. The procedures included an initial 15-minute recording to determine fetal baseline heart rate and variability. Oxytocin was administered via an infusion pump at a rate of 2 miU/min. The dosage was raised by l miU/min every 10 minutes until three uterine contractions of at least 40-second duration were recorded during a 10-minute period. At this stage oxytocin administration was discontinued, and fetal heart rate was monitored for an additional 20 minutes. After the initial 15-minute recording, the women allocated to the nipple stimulation group were instructed to rub the nipple of one breast for 15 minutes. If no adequate uterine activity was recorded, then both nip-
Contraction stress tests in fetal surveillance
Volume 157 Number 5
1179
30
25
en
*
!z2o
w i=
:
15
u.. o-
0 10
z
5 0
)0 END OF BREAST STIMULATION
60
120 90 MINUTES
150
180
210
Fig. 1. The cumulative success rates of the breast stimulation test (closed circles) and the oxytocin challenge test (open circles). (Asterisk = p < 0.0 I).
pies were stimulated for another 15 minutes. The fetal heart rate was monitored for 20 minutes after cessation of breast stimulation. Both the oxytocin challenge test and breast stimulation test were characterized as negative, positive, suspicious (irregular late or variable decelerations), hyperstimulated, and failed. Informed consent was obtained from all women enrolled in the study. All participants were instructed by a nurse before the start of the procedure. Statistical analysis. Statistical evaluation of the data was accomplished by the unpaired t test, the X2 test (Yates correction), and the Fisher exact test where applicable. Differences were considered statistically significant with p < 0.05. Results
The mean age of the two study groups was similar (28 ± 5.2 years for the oxytocin challenge test group and 29.7 ± 6.5 years for the breast stimulation test group). The parity of the two groups was similar. The distribution of the participants according to gestational age at the time of the study is shown in Table I. The success rates of the tests in the two groups according to gestational age are depicted in Table II. A satisfactory contraction stress test (three contractions per 10 minutes) was achieved in 21 (84%) gravidas in the breast stimulation test group and in 24 (96%) women in the oxytocin challenge test group. This difference was not statistically significant. All women in both groups acted in accordance with the study protocol, and none of the failures to achieve a contraction stress test could be attributed to inadequate compliance of the participants. Hyperstimulation of the uterus occurred once in each group. In both subjects at the end of the uterine
Table I. Distribution of the participants according to gestational age Gestational age (wk) ~37
38-40 ;;.41 Total
BST group
5
ll _j!
25
OCT group
6 14 _2
25
BST = Breast stimulation test; OCT = oxytocin challenge test.
tetany, the contraction stress test was accomplished without adverse results. The time intervals from the initiation of the test until adequate uterine stimulation are depicted in Fig. 1. In 10 (40%) gravidas of the breast stimulation test group, an adequate contraction stress test was obtained during the initial 15-minute period (single-nipple stimulation). Since according to the study protocol the breast stimulation test was planned for a duration of 30 minutes, we compared the number of satisfactory tests achieved during the first 30 minutes with each method. In the oxytocin challenge test group only four women had completed a contraction stress test as desired during this time period compared with 17 subjects in the breast stimulation test group (p < 0.01). Four additional patients in the breast stimulation test group achieved a contraction stress test during the 20-minute period after the cessation of nipple stimulation. At that time (50 minutes) only seven subjects in the oxytocin challenge test group had achieved a contraction stress test (p < 0.01). The mean time interval from the start of the contraction stress test until the achievement of three ...:ontractions within 10 minutes was 20.9 ± 11.5 min-
1180
Lipitz et al.
November 1987 Am J Obstet Gynecol
Table II. Outcome in each group in relation to gestational age ,;;37 wk
BST CST and one nipple stimulated CST and two nipples stimulated Tetanic contractions No. adequate uterine contractions Total OCT CST achieved Tetanic contractions No. adequate uterine contractions Total
38-40 wk
~41
6
2
3
5 2
2 1 2
6
Total (%)
wk
13 (52) 7 (28) 1 (4) __1_(l§L 25 (100)
2
12 1 1
5
23 (92) 1 (4) __ljiL_ 25 (100)
BST = Breast stimulation test; CST = contraction stress test; OCT = oxytocin challenge test.
Table III. Clinical outcome of the contraction stress tests in relation to gestational age* ,;;37 wk BST
Negative CST Positive CST Suspicious CST CST not achieved
4
I
38-40 wk
OCT
BST
6
8
I
1 2
~41
OCT
BST
11 1 1 1
7
I
wk
Total OCT
BST (%)
5
19 (76)
2
2 (8) 4 (16)
I
OCT(%) 22 1 1 1
(88) (4) (4) (4)
BST = Breast stimulation test; OCT = oxytocin challenge test; CST = contraction stress test. *Differences between groups not statistically significant.
utes in the breast stimulation test group and 81.3 ± 48.4 minutes in the oxytocin challenge test group. The clinical outcome of the tests was similar in the two groups (Table III). Uterine activity subsided shortly after the achievement of the contraction stress test, and no gravida went into spontaneous labor within 24 hours after the tests. Comment
Stimulation of the mammary nipple may lead touterine contractions during pregnancy, labor, and the postpartum period presumably via activation of the hypothalamus and the oxytocic neurons that end at the posterior pituitary gland. 13 However, studies have failed to detect significant elevations of endogenous oxytocin levels after nipple stimulation. 11 The contraction stress test has been widely accepted as a diagnostic tool for fetal well-being. During a contraction, uterine blood flow is temporarily decreased, which leads to a decline in fetal oxygenation." Although a healthy fetus tolerates these changes, a fetus already compromised by impaired uteroplacental perfusion may not be able to withstand a further decrease in oxygen supply, which will result in pathologic heart rate changes. The contraction stress test has been performed mainly by the intravenous infusion of oxytocin. The exogenous administration of oxytocin requires an intravascular line, accurate monitoring of the administration rate of the
potentially hazardous drug, a hospital bed, and a relatively long lag time from the start of administration until adequate uterine stimulation is achieved. The presented results confirm previous studies that concluded that the breast stimulation test overcomes some of these problems.7.8 The performance of the breast stimulation test was simple and less time-consuming when compared with the oxytocin challenge test whereas the clinical outcome was similar with both methods. The safety of the breast stimulation test is controversial. Since the endogenous secretion of oxytocin after nipple stimulation leads to persistent uterine contraction during the postpartum period, similar uterine stimulation prenatally may cause uterine hyperstimulation, tetanic contractions, and fetal compromise. 9 We elected to stimulate the nipple manually. Only one nipple was massaged for the first 15 minutes, and the mammae were stimulated subsequently for another 15 minutes or until the occurrence of t)l.ree uterine contractions within 10 minutes. In the present study only one patient in each group (4%) had tetanic contractions during the contraction stress test. Similar favorable results with the breast stimulation test have been reported. 7 • 9 • 11 However, Hill et a!. 12 have documented a high frequency of exaggerated uterine activity. The high success rate in achieving an adequate contraction stress test in both groups (84% for the breast
Contraction stress tests in fetal surveillance
Volume 157 Number 5
stimulation test and 96% for the oxytocin challenge test) is in accordance with previous studies. 7 • 8• 12 • 15 However, it should be noted that only seven of the women in the oxytocin challenge test group (28%) had an adequate contraction stress test within the first 50 minutes while all successful breast stimulation tests (21 of 25 patients, 84%) were achieved during the same time period (p < 0.01 ). Four of the contraction stress tests in the breast stimulation test group were achieved within 20 minutes of the cessation of nipple stimulation. Previous reports have emphasized the short time needed for the contraction stress test after the breast stimulation test. 7-9. 15 This randomized study demonstrates that the breast stimulation test is a satisfactory alternative to the oxytocjn challenge test. The breast stimulation test was found to achieve clinical results similar to the oxytocin challenge test, was less time-consuming, and was simpler to perform.
5.
6. 7. 8. 9. 10. 11.
12.
REFERENCES 1. Freeman RK. The use of the oxytocin challenge test for the antepartum clinical evaluation of the uteroplacental respiratory function. AM j 0BSTET GYNECOL 1975; 121: 481-9. 2. Garite TJ, Freeman RK, Hochleutner J, Linzey EM. Oxytocin challenge test: achieving the desired goals. Obstet Gynecoll978;51:614-8. 3. Keegan KA, Paul RH. Antepartum fetal heart rate testing. AMj 0BSTET GYNECOL 1980;136:75-80. 4. Freeman RK, Anderson G, Dorchester W. A prospective multiinstitutional study of antepartum fetal heart rate
13.
14. 15.
1181
monitoring. I. Risk of perinatal mortality and morbidity according to antepartum fetal heart rate results. AM J 0BSTET GYNECOL 1982;143:771-7. Freeman RK, Anderson G, Dorchester W. A prospective multiinstitutional study of antepartum fetal heart rate monitoring. II. Contraction stress test versus nonstress tests for primary surveillance. AM J OBSTET GYNECOL 1982; 143:778-81. Freeman RK. Contraction stress test for primary fetal surveillance in patients at high risk for uteroplacental insufficiency. Clin Perinatal 1982;9:265-70. Lenke RK, NemesJM. Use of nipple stimulation to obtain contraction stress test. Obstet Gynecol 1984;63:345-8. Hilddleston JF, Sutliff G, Robinson D. Contraction stress by intermittent nipple stimulation. Obstet Gynecol 1984; 63:669-73. Capelass EL, Mann Ll. use of breast stimulation for antepartum stress testing. Obstet Gynecol 1984;64:641-5. Erkkola R, Rintala H, Groenroos M. Breast stimulation test in fetal surveillance. Acta Obstet Gynecol Scand 1984;63:719-22. Viegas OAC, Amlkumaran S, Gibb DMF, Ratnil,m SS. Nipple stimulation in late pregnancy causing uterine hyperstimulation and profound fetal bradycardia, Br J Obstet Gynaecol 1984;91:364-6. Hill WC, Moenning RK, Katz M, Kitzmiller JZ. Characteristics of uterine activity during the breast stimulation stress test. Obstet Gynecol 1984;64:489-92. Wakerley JB, O'Neil) DS, Haar MB. Relationship between the suckling induced relei!,se of oxytocin and prolactin in the urethane-anesthesized lactating rat. J .Endocrinol 1978;76:493-500. Leake RD, Fisher DA, Ross M, Buster JE. Oxytocin secretory response to breast stimulation in pregnant women. AM j 0BSTET GYNECOL 1984; 184:259-62. Chayel} B, Scott E, Cheng CC, Perera C, Schiffer M. Contraction stress test by breast stim~lation as part of antepartum monitoring. Acta Obstet Gynecol Scand 1985; 64:3-6.
Key words: Fetal monitoring, oxytocin challenge test, breast stimulation test
The contraction stress test and the nonstress test are well-established diagnostic tools for the prenatal evaluation of the fetoplacental unit. 1-3 For practical reasons the nonstress test has been used in most centers as the first diagnostic test followed by a contraction stress test if a nonreactive pattern was obtained. 1 · 5 A contraction stress test is usually performed with either spontaneous uterine contractions or after induction of uterine activity by exogenous oxytocin infusion (oxytocin challenge test). 6 Recently several studies have indicated the efficacy of nipple stimulation for the initiation of uterine contractions, suggesting that the breast stimulation test is a convenient method of performing a contraction stress test. 7 - 10 The breast stimulation test, however, has been associated with a high incidence of uterine hyperstimulation.1I. 12 The purpose of this study was to compare prospectively the use of intravenously administered oxytocin to nipple stimulation for the induction of uterine activity in the performance of a contraction stress test.
Material and methods During the study period nonstress tests were performed on every gravida at a gestational age of 35 to From the Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, and the Sackler School of Medicine. Received for publication November 13, 1986; revised May 5, 1987; accepted june 18, 1987. Reprint requests: Shlomo Lipitz, M.D., Department of Obstetrics and Gynecology, Chaim Sheba Medical Center, Tel Hashomer, 52621 Israel.
1178
42 weeks either as a routine screening procedure at term or after the perception of decreased fetal movements. Subjects with multiple pregnancies, diabetes, hypertension, intrauterine growth retardation, or a pathologic nonstress test (defined as any type of deceleration) were-excluded from this study. Of the 210 subjects fulfilling these criteria, a nonreactive nonstress test was present in 50 patients. A reactive pattern was defined as two fetal heart rate accelerations in any 20minute period, with each acceleration rising at least 15 bpm above baseline and lasting for at least 15 seconds. The 50 patients with a nonreactive nonstress test underwent contraction stress tests. The participants were randomly divided; 25 underwent an oxytocin challenge test and the other 25 women had a breast stimulation test. All testing was performed with the patient in the left lateral recumbent position. The procedures included an initial 15-minute recording to determine fetal baseline heart rate and variability. Oxytocin was administered via an infusion pump at a rate of 2 miU/min. The dosage was raised by l miU/min every 10 minutes until three uterine contractions of at least 40-second duration were recorded during a 10-minute period. At this stage oxytocin administration was discontinued, and fetal heart rate was monitored for an additional 20 minutes. After the initial 15-minute recording, the women allocated to the nipple stimulation group were instructed to rub the nipple of one breast for 15 minutes. If no adequate uterine activity was recorded, then both nip-
Contraction stress tests in fetal surveillance
Volume 157 Number 5
1179
30
25
en
*
!z2o
w i=
:
15
u.. o-
0 10
z
5 0
)0 END OF BREAST STIMULATION
60
120 90 MINUTES
150
180
210
Fig. 1. The cumulative success rates of the breast stimulation test (closed circles) and the oxytocin challenge test (open circles). (Asterisk = p < 0.0 I).
pies were stimulated for another 15 minutes. The fetal heart rate was monitored for 20 minutes after cessation of breast stimulation. Both the oxytocin challenge test and breast stimulation test were characterized as negative, positive, suspicious (irregular late or variable decelerations), hyperstimulated, and failed. Informed consent was obtained from all women enrolled in the study. All participants were instructed by a nurse before the start of the procedure. Statistical analysis. Statistical evaluation of the data was accomplished by the unpaired t test, the X2 test (Yates correction), and the Fisher exact test where applicable. Differences were considered statistically significant with p < 0.05. Results
The mean age of the two study groups was similar (28 ± 5.2 years for the oxytocin challenge test group and 29.7 ± 6.5 years for the breast stimulation test group). The parity of the two groups was similar. The distribution of the participants according to gestational age at the time of the study is shown in Table I. The success rates of the tests in the two groups according to gestational age are depicted in Table II. A satisfactory contraction stress test (three contractions per 10 minutes) was achieved in 21 (84%) gravidas in the breast stimulation test group and in 24 (96%) women in the oxytocin challenge test group. This difference was not statistically significant. All women in both groups acted in accordance with the study protocol, and none of the failures to achieve a contraction stress test could be attributed to inadequate compliance of the participants. Hyperstimulation of the uterus occurred once in each group. In both subjects at the end of the uterine
Table I. Distribution of the participants according to gestational age Gestational age (wk) ~37
38-40 ;;.41 Total
BST group
5
ll _j!
25
OCT group
6 14 _2
25
BST = Breast stimulation test; OCT = oxytocin challenge test.
tetany, the contraction stress test was accomplished without adverse results. The time intervals from the initiation of the test until adequate uterine stimulation are depicted in Fig. 1. In 10 (40%) gravidas of the breast stimulation test group, an adequate contraction stress test was obtained during the initial 15-minute period (single-nipple stimulation). Since according to the study protocol the breast stimulation test was planned for a duration of 30 minutes, we compared the number of satisfactory tests achieved during the first 30 minutes with each method. In the oxytocin challenge test group only four women had completed a contraction stress test as desired during this time period compared with 17 subjects in the breast stimulation test group (p < 0.01). Four additional patients in the breast stimulation test group achieved a contraction stress test during the 20-minute period after the cessation of nipple stimulation. At that time (50 minutes) only seven subjects in the oxytocin challenge test group had achieved a contraction stress test (p < 0.01). The mean time interval from the start of the contraction stress test until the achievement of three ...:ontractions within 10 minutes was 20.9 ± 11.5 min-
1180
Lipitz et al.
November 1987 Am J Obstet Gynecol
Table II. Outcome in each group in relation to gestational age ,;;37 wk
BST CST and one nipple stimulated CST and two nipples stimulated Tetanic contractions No. adequate uterine contractions Total OCT CST achieved Tetanic contractions No. adequate uterine contractions Total
38-40 wk
~41
6
2
3
5 2
2 1 2
6
Total (%)
wk
13 (52) 7 (28) 1 (4) __1_(l§L 25 (100)
2
12 1 1
5
23 (92) 1 (4) __ljiL_ 25 (100)
BST = Breast stimulation test; CST = contraction stress test; OCT = oxytocin challenge test.
Table III. Clinical outcome of the contraction stress tests in relation to gestational age* ,;;37 wk BST
Negative CST Positive CST Suspicious CST CST not achieved
4
I
38-40 wk
OCT
BST
6
8
I
1 2
~41
OCT
BST
11 1 1 1
7
I
wk
Total OCT
BST (%)
5
19 (76)
2
2 (8) 4 (16)
I
OCT(%) 22 1 1 1
(88) (4) (4) (4)
BST = Breast stimulation test; OCT = oxytocin challenge test; CST = contraction stress test. *Differences between groups not statistically significant.
utes in the breast stimulation test group and 81.3 ± 48.4 minutes in the oxytocin challenge test group. The clinical outcome of the tests was similar in the two groups (Table III). Uterine activity subsided shortly after the achievement of the contraction stress test, and no gravida went into spontaneous labor within 24 hours after the tests. Comment
Stimulation of the mammary nipple may lead touterine contractions during pregnancy, labor, and the postpartum period presumably via activation of the hypothalamus and the oxytocic neurons that end at the posterior pituitary gland. 13 However, studies have failed to detect significant elevations of endogenous oxytocin levels after nipple stimulation. 11 The contraction stress test has been widely accepted as a diagnostic tool for fetal well-being. During a contraction, uterine blood flow is temporarily decreased, which leads to a decline in fetal oxygenation." Although a healthy fetus tolerates these changes, a fetus already compromised by impaired uteroplacental perfusion may not be able to withstand a further decrease in oxygen supply, which will result in pathologic heart rate changes. The contraction stress test has been performed mainly by the intravenous infusion of oxytocin. The exogenous administration of oxytocin requires an intravascular line, accurate monitoring of the administration rate of the
potentially hazardous drug, a hospital bed, and a relatively long lag time from the start of administration until adequate uterine stimulation is achieved. The presented results confirm previous studies that concluded that the breast stimulation test overcomes some of these problems.7.8 The performance of the breast stimulation test was simple and less time-consuming when compared with the oxytocin challenge test whereas the clinical outcome was similar with both methods. The safety of the breast stimulation test is controversial. Since the endogenous secretion of oxytocin after nipple stimulation leads to persistent uterine contraction during the postpartum period, similar uterine stimulation prenatally may cause uterine hyperstimulation, tetanic contractions, and fetal compromise. 9 We elected to stimulate the nipple manually. Only one nipple was massaged for the first 15 minutes, and the mammae were stimulated subsequently for another 15 minutes or until the occurrence of t)l.ree uterine contractions within 10 minutes. In the present study only one patient in each group (4%) had tetanic contractions during the contraction stress test. Similar favorable results with the breast stimulation test have been reported. 7 • 9 • 11 However, Hill et a!. 12 have documented a high frequency of exaggerated uterine activity. The high success rate in achieving an adequate contraction stress test in both groups (84% for the breast
Contraction stress tests in fetal surveillance
Volume 157 Number 5
stimulation test and 96% for the oxytocin challenge test) is in accordance with previous studies. 7 • 8• 12 • 15 However, it should be noted that only seven of the women in the oxytocin challenge test group (28%) had an adequate contraction stress test within the first 50 minutes while all successful breast stimulation tests (21 of 25 patients, 84%) were achieved during the same time period (p < 0.01 ). Four of the contraction stress tests in the breast stimulation test group were achieved within 20 minutes of the cessation of nipple stimulation. Previous reports have emphasized the short time needed for the contraction stress test after the breast stimulation test. 7-9. 15 This randomized study demonstrates that the breast stimulation test is a satisfactory alternative to the oxytocjn challenge test. The breast stimulation test was found to achieve clinical results similar to the oxytocin challenge test, was less time-consuming, and was simpler to perform.
5.
6. 7. 8. 9. 10. 11.
12.
REFERENCES 1. Freeman RK. The use of the oxytocin challenge test for the antepartum clinical evaluation of the uteroplacental respiratory function. AM j 0BSTET GYNECOL 1975; 121: 481-9. 2. Garite TJ, Freeman RK, Hochleutner J, Linzey EM. Oxytocin challenge test: achieving the desired goals. Obstet Gynecoll978;51:614-8. 3. Keegan KA, Paul RH. Antepartum fetal heart rate testing. AMj 0BSTET GYNECOL 1980;136:75-80. 4. Freeman RK, Anderson G, Dorchester W. A prospective multiinstitutional study of antepartum fetal heart rate
13.
14. 15.
1181
monitoring. I. Risk of perinatal mortality and morbidity according to antepartum fetal heart rate results. AM J 0BSTET GYNECOL 1982;143:771-7. Freeman RK, Anderson G, Dorchester W. A prospective multiinstitutional study of antepartum fetal heart rate monitoring. II. Contraction stress test versus nonstress tests for primary surveillance. AM J OBSTET GYNECOL 1982; 143:778-81. Freeman RK. Contraction stress test for primary fetal surveillance in patients at high risk for uteroplacental insufficiency. Clin Perinatal 1982;9:265-70. Lenke RK, NemesJM. Use of nipple stimulation to obtain contraction stress test. Obstet Gynecol 1984;63:345-8. Hilddleston JF, Sutliff G, Robinson D. Contraction stress by intermittent nipple stimulation. Obstet Gynecol 1984; 63:669-73. Capelass EL, Mann Ll. use of breast stimulation for antepartum stress testing. Obstet Gynecol 1984;64:641-5. Erkkola R, Rintala H, Groenroos M. Breast stimulation test in fetal surveillance. Acta Obstet Gynecol Scand 1984;63:719-22. Viegas OAC, Amlkumaran S, Gibb DMF, Ratnil,m SS. Nipple stimulation in late pregnancy causing uterine hyperstimulation and profound fetal bradycardia, Br J Obstet Gynaecol 1984;91:364-6. Hill WC, Moenning RK, Katz M, Kitzmiller JZ. Characteristics of uterine activity during the breast stimulation stress test. Obstet Gynecol 1984;64:489-92. Wakerley JB, O'Neil) DS, Haar MB. Relationship between the suckling induced relei!,se of oxytocin and prolactin in the urethane-anesthesized lactating rat. J .Endocrinol 1978;76:493-500. Leake RD, Fisher DA, Ross M, Buster JE. Oxytocin secretory response to breast stimulation in pregnant women. AM j 0BSTET GYNECOL 1984; 184:259-62. Chayel} B, Scott E, Cheng CC, Perera C, Schiffer M. Contraction stress test by breast stim~lation as part of antepartum monitoring. Acta Obstet Gynecol Scand 1985; 64:3-6.