Antepartum fetal testing I. The oxytocin M.



challenge test







St. Pa,ul, Minmotrc TWO hundred seventy-eight high-risk patients were managed by a comprehensive assessment of the anatomic, biochemical, and functional environment of the fetoplacental unit utilizing predetermined guidelines. Decisions to terminate pregnancy were rese&ed for patients who demonstrated a positive OCT. Perinatal outcome in patients with positive OCT’s was sigr@canUy worse than in patients who did not have a positive OCT. Patients with suspic~us OCT’s frequently had positive OCT’s and were more likely to bear growth-retarded infants, whereas rq#itivs OCT’s in general were associated with a favorable outcome. Correlation of estriol excretion with the OCT and perinatal outcome was inconsistent. There were a total of four prenatal deaths, all of which were considered unpreventable. (AM. J. OBSTET. GYNECXX. 134532, 1979.)

A COMPREHENSIVE approach to the antepartum assessment of the intrauterine environment consists of adequate evaluation of the anatomic, biochemical, and functional status of the fetoplacental unit. In this institution, anatomic assessment involves routine ultrasound cephalometry during early gestation.’ Biochemical tests include 24 hour urinary estriol determinations,2 and amniotic fluid analysis for both the L/S ratio” and spectrophotometric analysis in instances 01’ Rh isoimmunization.’ Functional evaluation involves electronic monitoring of the fetal heart rate (FHR) for periodic changes in response to oxytocin-irlduced uterine contractions, the oxytocin challenge test,” and for accelerations in response to fetal movements,” a “nonstress” test. With this information provided the task would be primarily to determine whether the intrauterine environment has been sufficiently compromised to warrant From The Prrinatal Center, C$wcology, St. Paul-Ramsey CtW~~.

Department Hospita.1

of Obstrtnrs

and Medical

Supported by Grant No. 8OlDli8 jrom the Medxal Education and Research Foundation, St. Paul-Rarns~y Hospital and Medical Centrr. Rwiued

for public&on




21, 1978.

43 1978.

Reprint requesti: Dr. M. Ismuil Barrada, Dwector, Obstetrical Division, Perinutal Center, St. Paul-Ramsey Hospital, 640Jachson St., St. Paul, Minnesota 55101.



termination of the pregnancy, and then to select the appropriate time for intervention. The present study was undertaken in order to evaluate the role of the functional methods of assessing the pregnancy at risk for fetal compromise and will be reported in two parts: Part I describes the experience and pregnancy outcome in patients who have undergone an oxytocin challenge test ((XT) and Part II describes the experience with a standardized nonstress test (NST).

Material and methods During the interval betweenJanuary, 1974, and July, 1977, a total of 420 0C’I”s were performed on 278 patients who were considered at risk for a c-ompromised fetoplacental unit. Patients selected for this test were admitted to the labor and delivery ward and were positioned at a comfortable recumbancy (approximately SO to 40 degrees) with a slight left tilt. A continuous recording of the fetal heart rate (FHR) and uterine activity was accomplished by means ot‘ a Koche Fetal Monitor, Model Number 2102 or 2104. Maternal vital signs, including blood pressure, pulse, and temperature, were recorded at the outset and the blood pressure at periodic intervals for the duration of the test. Oxytocin was administered with a Harvard constant-rate infusion pump, and the rate was increased at I 5 minute intervals until uterine contractions occurred

Volume Number

154 .i

approximately every three minutes. The oxytocin infusion was discontinued when a recorded segment of one-half hour was available for analysis. Patients were subsequently observed while still being monitored until uterine activity subsided, and thereafter the test was terminated. Tests were interpreted as being positive, negative, suspicious, hyperstimulation, or inadequate as follows: (1) positive: repetitive late decelerations with most uterine contractions; (2) negative: no FHR abnormalities with apparently adequate uterine contractions; (3) suspicious: occasional late decelerations; (4) hyperstimulation: FHR deceleration in response to a prolonged uterine contraction, or late decelerations occurring with uterine contractions observed at intervals of two minutes or less, and (5) inadequate: technical difficulties or instances in which the uterus was unresponsive to oxytocin. Whenever possible, patients scheduled for an OCT underwent a 24 hour urinary estriol determination on a sample collected the day prior to the test. In most patients the OCT was repeated at weekly intervals. In some instances, however, such as diabetes mellitus, severe hypertension, Rh sensitization, low or falling estriol levels, and suspicious OCT’s, or when the intrauterine environment was considered unusually precarious, the test was repeated at more frequent intervals. Management was determined on the basis of the results of the OCT in conjunction with other laboratory tests and the overall clinical picture. Patients who showed a negative OCT with normal estriols had repeat testing at weekly intervals, and with low or falling estriols were tested more frequently. Patients who demonstrated a positive OCT underwent an L/S ratio determination. If the L/S ratio was mature, delivery was planned either by oxytocin induction of labor when the cervix was favorable, or by cesarean section when the cervix was unfavorable or when the oxytocin induction was judged to be unduly hazardous to the fetus. If in the ensuing induction following a positive OCT late decelerations were not observed, the procedure was discontinued and the test considered false positive. If, however, late decelerations persisted in the ensuing induction, a presumption of a diminished fetal metabolic reserve was entertained, oxytocin discontinued, and a cesarean section undertaken. If the L/S ratio was immature, betamethasone induction of pulmonary surfactant, according to the protocol described by Liggins and Howie,’ was instituted and delivery was planned 48 hours after the initiation of therapy. In the interim, patients were continuously monitored. Patients who demonstrated a suspicious test were re-



Table I. Number of patients and OCT’s according to groups* and type of test Group


35 77 37 26 10 0 4

No. of Patients No. of tests Positive Negative Suspicious Hyperstimulation Inadequate *For description


93 I46 0 127 7 .i 7








1.50 202 0 179 9 4 10


278 425 37 332 26 9 21

of groups see text

Table II. Distribution of patients with positive OCT according to management and outcome

No. of Patients 11


Prompt cesarean section


No interventionFetal death in utero


InductionNo fetal distress*


InductionPersistent fetal distress


2-High-risk fetus g-unfavorable cervix I-Maternal viral pneumonia l-Fetal anomaly 3-Vaginal delivery 2--Cesarean section for cephalopelvic disproportion 15-Cesarean section 2-Vaginal delivery

*False positive 5/22 = 22.7%. tested more frequently, and further management determined according to results of the repeated tests. Patients who showed a hyperstimulation or inadequate test were retested at a convenient time in the ensuing days. In spite of the adoption of these seemingly allinclusive guidelines, it was necessary on occasion to modify the management based on the clinical condition of the individual patient. Newborn infants were admitted to the neonatal division of the Perinatal Center, and underwent a complete physical and neurologic examination at an appropriate time after birth. Disturbances in growth characteristics were classified into: intrauterine growth retardation (IUGR) and large for gestational age (LGA), based on the criteria set forth by Usher and McLean8 and dysmaturity as described by Clifford.”

Results The total number of patients were divided into three groups: Group I consisted of 35 patients who demonstrated at least one positive OCT; Group II consisted of 93 patients who had no positive OCT’s, and whose pregnancies were complicated by diabetes mellitus, severe hypertension, severe pre-eclampsia, or low or falling estriols, in addition to those pregnancies which resulted in the birth of a neonate with IUGR, LGA, or


Barrada, Edwards, and Hakanson

Table III. Comparison of outcome between patients with positive OCT and no posiLive OCl

I--Cesarean section Meconium Estriol: low and falling IUGR Dysmaturity LGA Apgar: I min. i 6 5 min. G 6

Positive OCT (Number = 21)

No positivr OCT (Num-



19 9 8 6 6 1 8 4


90.5 42.9 38.1 28.6 28.6 4.8 38.1 19.0

hrr = 243)

41 51 36 17 36 13 30 8



16.9 21.1 15.1 7.0 14.9 5.4 12.4 3.3

Antepartum fetal testing. I. The oxytocin challenge test.

Antepartum fetal testing I. The oxytocin M. ISMAIL LAURA ERICK challenge test BARRADA, E. M.D. EDWARDS, M.D. 1’. HAKANSONV, M.D. St. Pa,ul,...
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