Fetal heart rate deceleration patterns duringantepartum nonstress testingCATHERINE MOLLOY, DD.RICHARD BERNSTINE, M.D.Youngstown, Ohio

During a 24-month-period, 1,980nonstress tests were completed on1,054 high-risk pregnant women. Aretrospective review of these testswas conducted to determine theincidence of spontaneousdecelerations, and the group ofpatients in whom spontaneousdecelerations occurred wascompared to the remainder of thepopulation. Spontaneousdecelerations occurred in 21 percentof the population of this group; two-thirds were considered to be minor(amplitude of 10-20 beats and lastingless than 60 seconds) and one-thirdwere major (greater than 20 beatsbelow baseline and lasting more than1 minute). The group of infants whohad major spontaneous decelerationson NST had more cord complicationsand lower Apgar scores, and theirperinatal mortality was increasedfourfold over infants who did notexhibit these changes.

The occurrence of spontaneous decelerations dur-ing nonstress testing (NST) are mentioned in sev-eral reports on antepartum monitoring,' but theproblem is discussed in detail in only a small num-ber of reports.' In a recent article, Pazos and as-sociates' demonstrated increased fetal mortalitywhen spontaneous decelerations occurred duringnonstress tests that were performed within 1 weekof delivery. They associated the higher fetal mor-tality rates with cord complications and intrauter-ine growth retardation. Kubli and coworkers' de-scribed late decelerations in relation to Braxton-Hicks contractions occurring during NST andbelieved that they represented a terminal patternthat was associated with a disastrous fetal out-come.

The present study was undertaken to ascertainthe relationship of spontaneous deceleration dur-ing NST to fetal outcome and its association withantecedent factors.

Materials and methodsThe present study was conducted retrospectivelyon 1,980 nonstress tests, which were performed on1,054 patients during a 24-month period betweenApril 1, 1980, and April 1, 1982. The cases were de-rived from the private practice of 14 obstetriciansand the hospital's ambulatory clinic. The indica-tions for NST are presented in Table 1.

Intrauterine growth retardation was clinicallysuspected when there was lack of progressivegrowth of the uterus or failure of the mother togain weight. Postdatism was suspected when thepregnancy extended beyond the expected date ofconfinement, as confirmed by an examination ear-ly in pregnancy or by a sonogram in the first half ofpregnancy.

Spontaneous decelerations were considered to beminor if they lasted 15 to 60 seconds and had anamplitude of 10 to 20 beats below baseline; majordecelerations exceeded 60 seconds in duration andwere more than 20 beats below baseline (Fig. 1).These criteria were selected following review ofthe literature; they had been utilized in a similarfashion by several authors.'"-13 Those patientswho demonstrated major decelerations comprisedthe study group (SDG), and all other patients wereincluded in the control group (CG).

There were 1,564 tests on 833 patients in thecontrol group (CG) and 416 tests on 221 patientswho demonstrated spontaneous decelerations. Inthe major spontaneous deceleration group, 138tests were performed on 74 patients. Ninety per-cent of the patients had 1 or 2 nonstress tests, butas many as 10 tests were performed on some pa-tients. In general, NST was performed at weeklyintervals.

At the time of performance of NST, results wereinterpreted by a senior resident. For purposes ofthis paper, all tests that demonstrated spontane-ous decelerations were reviewed in their entiretyby one author, and the interpretation was con-

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TABLE 1. INDICATION FOR NONSTRESS TESTING IN 1,054 PATIENTS.

Indication

Group

Decreasedfetal

movement DiabetesPregnancy-induced

hypertension Postdatism

Intrauterinegrowth

retardation Miscellaneous* Total

Spontaneousdecelerationgroup (19.5%) (8%) (12%) (19.5%) (7%) (34%) (100%)

Control group(no spontaneousdeceleration) (14%) (4.3%) (12%) (36%) (3.7%) (30%) (100%)

*This category includes previous stillbirth, auto accident, cardiorespiratory disease, urinary tract infection/disease, hepatic disease, and collagenvascular disease.

Fig. 1. Fetal heart monitoring exemplifies a major decelerationlasting longer than 60 seconds with greater than 20 beats belowbaseline.

firmed. All other nonstress tests were reviewedcompletely by a medical student, and a sample of20 percent was examined by one author.

The presence or absence of decelerations as wellas reactivity of the test was reported to the attend-ing obstetrician at the time of recording of NST.The management of the individual patient was de-cided by the attending physician on the basis of theresult of NST, the presence/absence of spontane-ous decelerations, and the patient's status. No uni-formity of management was evident.

All tests were performed with a Corometrics 110antepartum fetal monitor. The fetal heart rate wasmonitored by an ultrasonic transducer, and uter-ine activity was recorded by an external tocodyna-mometer. In addition, the mother indicated fetalactivity by depressing an event marker. All pa-tients were in the semirecumbent position.

Criteria for reactive NST were 2 or more fetalheart accelerations of 15 beats or more per minute,which lasted at least 15 seconds, in response to fe-tal activity over a period of 20 minutes. If the fetusdid not exhibit this pattern, the test was continuedfor an additional 20 minutes following fetal stimu-lation. If accelerations again were not observed,the NST was recorded as nonreactive. The laborand delivery summary charts of all patients and

the newborn records were reviewed retrospective-ly. Ninety-five percent of patients were monitoredduring labor.

ResultsNonstress testingInterpretations of the 1,980 nonstress tests arepresented in Table 2. According to previously stat-ed criteria, 97 percent of the tests were reactive.The unsatisfactory tests were excluded from calcu-lation of percentages for subsequent categories.The baseline fetal heart rate and variability werewithin normal limits. Twenty-two percent of pa-tients had at least 1 uterine contraction duringNST. Of these women, 4 percent exhibited decel-erations of the fetal heart rate with the uterinecontractions. Seven percent of tests demonstrated3 or more spontaneous contractions in 10 minutes,thus meeting the criteria for contraction stresstesting.

Spontaneous decelerations that were not associ-ated with either fetal movement or uterine con-tractions occurred in 21 percent of the patients;two-thirds of these were of a minor and one-thirdof a major degree. The patients with spontaneousmajor decelerations, who constituted the SDG, hadreactive NST in 93 percent of instances.

Thee were 15 patients who exhibited major de-celerations on more than one test. Table 3 summa-rizes the data for this group. Once spontaneous de-celerations appeared on NST, they persisted onsubsequent tests.

Only 1 woman in this group had a nonreactivetest. Her labor was complicated by late decelera-tions, and cesarean section was performed. TheApgar score was low (5) at birth, but the baby sur-vived. There was 1 stillbirth, in a patient who not-ed decreased fetal movement over a 4-week period.She had spontaneous decelerations in 5 of 7 non-stress tests, all of which were reactive. There was 1

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TABLE 2. RESULTS OF 1,980 NONSTRESS TESTS.

. Parameter Criteria PercentInterpretation Unsatisfactory 1.04*

Nonreactive 1.61Reactive 97.35

Baseline fetal heart rate 120-160 beats/minute 99.2>160 beats/minute 0.6<120 beats/minute 0.2

Baseline variability 5 to 20 beats/minute 98.5<5 beats/minute 1.5

Uterine contractions None 78.2<3 per 10 minutes 14.503 per 10 minutes 7.3

Fetal heart rate changewith uterine contractions <15 beats and/or 15 seconds 87.2

..?-15 beats and 15 seconds 8.9Deceleration between 10-20

beats and 15-60 seconds 3.4Deceleration >20 beats

and 60 seconds 0.5Spontaneous deceleration None 79.0

10-20 beats and 15-60 seconds (minor) 14.0>20 beats and 60 seconds (major) 7.0

*Excluded from subsequent data and calculation of percentages.

TABLE 3. DATA FOR 15 PATIENTS WHO DEMONSTRATED SPONTANEOUS DECELERATION ON MULTIPLE NONSTRESS TESTS.

Tests withspontaneousdeceleration(total no. of Interval from last Apgar score

Patient tests) Results of NST test to delivery Fetal monitoring in labor (1-5 minutes) Comment

JB 3(5) Reactive 1 day Variable deceleration 9-9LC 3(6) Reactive 1 week No abnormality 7-9DH 4(10) Reactive 1 week Late deceleration 9-9 Small for

gestational ageMI 2(5) Reactive 2 months No abnormality 8-9PL 3(9) Reactive 6 weeks No abnormality 8-9PM 2(2) Reactive 3 days No abnormality 8-9CM 2(7) Reactive 3 days No abnormality 8-9LM 2(2) Reactive/ 4 days Late deceleration, 5-8

Nonreactive cesarean sectionCCM 2(4) Reactive 1 day No abnormalities 9-9 •

BO 2(6) Reactive 5 days No abnormalities 9-9 Failureof descent

SR 2(5) Reactive 6 weeks No abnormalities 8-8DR 3(3) Reactive 2 days No labor 6-8 Repeat

cesareansection

CR 5(7) Reactive 8 days Fetal demise prior to Stillborn Decreasedlabor fetal

movement,vasa praevia

NS 3(7) Reactive 3 days Bradycardia, variable 8-9deceleration

CZ 3(8) Reactive 1 week Late deceleration 5-9

patient with vasa praevia, which ruptured duringlabor and was followed by fetal death prior to hos-pital admission.

Clinical dataThe mean age of patients in the SDG was 26+years, while that of the CG was 24+ years. The dif-ference was •secondary to the percentage of pa-tients 35 years and older; in the SDG it was 11.3

percent, as compared to 3.6 percent in the CG (p <.001).

There were a greater percentage of diabetic (7percent versus 4.3 percent, p < .01) and pre-eclamptic patients (11 percent versus 2 percent, p <.05) in the SDG. In all other clinical aspects, thegroups were comparable.

There was no difference in the incidence of in-duced labor between groups. The course during la-

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bor as described by the Friedman curve was simi-lar in both groups. Abnormal labor patterns wereobserved with equal frequency in each group.

Intrapartum monitoring of the fetus during la-bor was performed in almost all instances. Abnor-mal patterns, including decreased baseline vari-ability, prolonged bradycardia or tachycardia, andlate or variable decelerations occurred in approxi-mately 20 percent of patients in each group. Scalpfetal blood pH determinations were performed inonly a small number of patients.

Delivery by cesarean section was more frequentin the SDG (42.4 percent) than the CG (29.8 per-cent) (p < .01). This difference was primarily dueto a higher incidence of primary cesarean section(34.4 percent in the SDG as compared to 23 percentin the CG). The institutional primary cesareansection rate was 12 percent during this time pe-riod.

Diabetes as an indication for primary cesareansection occurred more frequently in the SDG (10percent versus 2 percent, p < .05). No other differ-ences were observed.

The percentage of low Apgar scores (./ 6) at both1 minute (19.8 percent versus 13.5 percent) and 5minutes (4.7 percent versus 2.8 percent) weregreater in the SDG than the CG (p < .05). Thepresence of nuchal cord was greater in the SDGthan the CG (31.2 percent versus 23.4 percent, p <.05). No difference between groups was observed inthe presence of meconium in the amniotic fluid.

Perinatal mortality (early neonatal period only)was increased fourfold (18.8 from 4.6) when 1 ormore spontaneous decelerations were present inNST, as compared to the mortality rate when nonewas observed (p < .001).

Although the suspicion of postmaturity as an in-dication for NST accounted for 19 percent and 36percent of the SDG and the CG, respectively, theexamination of the newborn infant did not confirmthe diagnosis in most instances. Only 3.8 percentof the SDG and 2.9 percent of the CG met Clif-ford's' criteria for postmaturity.

In view of the literature relating decelerationsto Braxton-Hicks contractions on NST and disas-trous fetal outcomes, we examined separately thedata of a group of 47 patients who demonstratedsuch deceleration patterns. The parameters stud-ied revealed no difference when compared to theCG as to maternal age, primiparity, monitoringabnormalities during labor, method of delivery,Apgar scores, cord complications, or low birthweights.

DiscussionSeveral reports have indicated an association be-

tween the presence of spontaneous decelerationsduring nonstress testing and fetal problems. Phe-lan and Lewis" reviewed 2,000 nonstress testsand correlated fetal heart rate decelerations withabnormal cord position, including nuchal, truncal,and funic, as well as true knots of the cord. Ourdata confirm only the higher incidence of nuchalcords. Bruce, Petrie, and Davison' found a higherrisk of intrapartum cord complications for smallfor gestational age and postdated fetuses whenvariable decelerations were present on NST. Pazosand coauthors8 reported a correlation betweenspontaneous decelerations and intrauterinegrowth retardation resulting in increased perina-tal mortality. We did not observe similar statisti-cally significant differences. Visser and associ-ates state that isolated nonrepetitivedecelerations are not associated with distress dur-ing labor, except in growth retarded infants. Trim-bos and Keirse" found no correlation betweenspontaneous decelerations and fetal distress.

The present data indicate that spontaneous de-celerations occurring during NST is not a rare phe-nomenon (7 percent); once such changes are pres-ent, they do not disappear on subsequent NST.Their repetitive occurrence does not change theirprognostic importance.

The combination of decelerations occurring inassociation with Braxton-Hicks contractions hasbeen designated as a terminal fetal pattern. Em-men and coworkers' suggest immediate deliverywhen late decelerations are accompanied by thedisappearance of beat to beat variability. Fair-brother and associates' reported 2 fetal deaths in4 instances when this pattern was observed duringNST. Visser and Huisjes21 included the terminalpattern in their classification of nonstress testsand concurred in the recommendation of immedi-ate delivery. We observed this pattern in 47 in-stances and were unable to demonstrate any sig-nificant difference in fetal outcome from thecontrol group.

SummaryMajor spontaneous fetal heart rate decelerationsoccurred in 74 of 1,054 high-risk patients (7 per-cent) in the present study. Infants who demon-strate major spontaneous decelerations on NSThave more cord complications and lower Apgarscores. Their perinatal mortality incidence is in-creased fourfold over infants who do not exhibitthese changes. The mothers are older and are morelikely to be diabetic.

1. Sureau, C., et al.: Diagnostic cardiotocography. In reviews in perina-

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tal medicine, edited by E.M. Scarpelli and E.V. Cosmi. Raven Press,New York, 1978, vol. 2. pp. 57-1022. Caldeyro-Barcia, R.: La frequence du coeur foetal pendant l'accouche-ment. Bull Fed Gyn Obst Franc 17:395, 19653. Hon, E.H.: Fetal heart rate monitoring. In modern perinatal medi-cine, edited by L. Gluck. Year Book Medical Publishers, Chicago, 1974,pp. 139-1474. Freeman, R.K.: The clinical value of antepartum fetal heart ratemonitoring. In Modern perinatal medicine, edited by L. Gluck. YearBook Medical Publishers, Chicago, 1974, pp. 163-1775. Pose, S.V., et al.: Test of fetal tolerance to induced uterine contrac-tions for the diagnosis of chronic distress. In Perinatal factors affectinghuman development. Scientific publication no. 185. Pan AmericanHealth Organization, Washington, D.C., 1969, p. 96O. Kubli, F.W., Kaeser, 0., and Hinselman, M.: Diagnostic managementof chronic placental insufficiency. In The foeto-placental unit, edited byA. Pecile and C. Finzi. Excerpts Medics Foundation, Amsterdam, 1972,p. 3237. Ray, M., et al.: Clinical experience with the oxytocin challenge test.Am J Obstet Gynecol 114:1-9, Sep 728. Pazos, R., et al.: Association of spontaneous fetal heart rate decelera-tions during antepartum nonstress testing and intrauterine growth re-tardation. Am J Obstet Gynecol 144:574-7, 1 Nov 829. Kubli, F., et al.: Die antepartale fetale Herzfrequenz. II. Verhaltenvon Grundfrequenz. Fluktuation and Dezelerationen bei antepartalemFruchttod. Z Geburtshilfe Perinatol 176:309-23, Aug 7210. Merkur, H.: Normal and abnormal antenatal ultrasonic cardio-graphic patterns. Br J Obstet Gynaecol 86:533-9, Jul 7911. Goupil, F., et al.: Antepartum fetal heart rate monitoring. Decel-eration patterns. Eur J Obstet Gynaecol Reprod Biol 11:239-49, Feb 8112. Krebs, H.B., and Petres, R.E.: Clinical application of a scoring sys-tem for evaluation of antepartum fetal heart rate monitoring. Am J Ob-stet Gynecol 130:765-72, 1 Apr 7813. Dawes, G.S., et al.: Pattern of the normal human fetal heart rate. BrJ Obstet Gynaecol 89:270-5, Aug 82

14. Clifford, S.H.: Postmaturity. Adv Pediatr 9:13-63, 195715. Phelan, J.P., and Lewis, P.E.: Fetal heart rate decelerations duringa nonstress test. Obstet Gynecol 57:228-32, Feb 8116. Bruce, S.L., Petrie, R.H., and Davison, J.: Prediction of abnormalumbilical cord position and intrapartum cord problems from the non-stress test. Diagn Gynecol Obstet 2:47-9, Spring 8017. Visser, G.H., et al.: Nonstressed antepartum heart rate monitoring.Implications of decelerations after spontaneous contractions. Am J Ob-stet Gynecol 138:429-35, 15 Oct 8018. Trimbos, J.B., and Keirse, M.J.: Nonspecific decelerations in fetalheart rate during high risk pregnancy. Br J Obstet Gynaecol 84:732-6,Oct 7719. Emmen, L., et al.: Antepartum diagnosis of the "terminal" fetalstate by cardiotocography. Br J Obstet Gynaecol 82:353-9, May 7520. Fairbrother, P.F., et al.: The significance of prelabour type II decel-eration of fetal heart rate in relation to Braxton-Hicks contractions. Re-port of four patients. S Afr Med J 48:2391-3, 30 Nov 7421. Visser, G.H., and Huisjes, H.J.: Diagnostic value of the unstressedantepartum cardiotocogram. Br J Obstet Gynaecol 84:321-6, May 77

Accepted for publication in June 1985. Updating, as necessary,has been done by the authors.

Dr. Molloy is an attending physician in the Department of Ob-stetrics-Gynecology at St. Elizabeth Hospital Medical Center inYoungstown, Ohio, and an instructor of obstetrics-gynecologyat Northeastern Ohio Universities College of Medicine inRootstown, Ohio. Dr. Bernstine is the director of education inthe Department of Obstetrics-Gynecology at St. Elizabeth Hos-pital Medical Center and a professor of obstetrics-gynecology atNortheastern Ohio Universities College of Medicine.Dr. Molloy, 4800 Market Street, Youngstown, Ohio 44512.

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