Papers of the Society for Gynecologic Investigation

Fetal breathing movements and the abnormal contraction stress test F R A:\ K A. 1\f A I\ N I :\' G, :M . D. *

l.A\VRENCE D. PLATT. M.D. Lo1 A ngtln. Colifomiu The presence or absence of fetal breathing movements (FBMs) in a 30 minute observation period was determined in 29 patients with abnormal contraction stress tests (CSTs). The study population included 14 patients with positive CSTs, 11 patients with equivocal CSTs, and four patients with unclassified CSTs. In patients with either an equivocal or a positive CST, the presence of FBMs was associated with a high incidence of false predictive tests. Conversely, the absence of FBMs in a patient with a positive CST was uniformly associated with intrapartum fetal distress. The presence or absence of FBMs was not helpful in assessing the patients with unclassified CSTs. These data suggest FBMs may be a useful means of evaluating the patient with a positive or equivocal CST. (AM. J. 0BSTET. GYNECOL. 133:590, 1979.)

Co!'.'TII\OUS I~TRAPARTCM fetal heart rate (FHR) monitoring has proved to be a valuable means of assessing fetal condition. The presence of FHR variability and the absence of periodic FHR changes is a reiiabie index of fetal well-being. 1 The loss of FHR variabilitv and the presence of repetitive late decelerations ha' been associated with increased fetal morbiditv and mortality rates, although the relationship is neither simple nor direct. 1. 2 The FHR response to uterine contractions in the antepartum period (oxytocin challenge test or contraction stress test [CST]) was introduced as a test of fetal reserve by Ray and associates a Accumulated experience with the CST indicates the incidence of false positive tests is at least 25~1r. 4 From the L'nic•ersity of Southern Calijomia, Scfwol of Mediciue, TVomen's Hospital. Presented at the Twenty-fifth Annual iHeeting of thr Societ_l'for G)•necologic lm•estigation. Atlanta, Georgia. :'v!arch 15-18, 1978.

Reprint requesl-1: Dr. Frank A. :Hanning, Unic•enit> of Southern Caltfornht. Scl'wol t~{ Afedicine. fVomeH's HwfJita/, 1240 lVo. Mission Road, Los Arzr;e/e1. Califumia 90033.

*Supported by o grant from the 1Yational Foundation-.'Harch of Dimes.


Breathing movements are a normal component of intrauterine development in the uncompromised fetus." The presence of fetal breathing movements (FBMs) appears to refiect fetai heaith. 6 • 7 Hypoxemia and acidemia reduce or abolish FBMs in animal fetu~es. 8 The fall in FBMs after smoking and the absence of FBMs with spontaneous maternal hypoxemia suggest that fetal hypoxemia may suppress human FBMs.~· 10 The purpose of this study was to evaluate FBMs in patients with an abnormal CST.

Methods Patient selection. The presence or absence of FBMs was determined in 29 consecutive patients with abnormal CSTs. All patients had a nonstress test (NST) before a CST was performed. The XST was termed "reactive" if there were five or more accelerations of the fetal heart rate of 15 bpm or greater with fetal movement in a 20 minute period. A NST that did not meet these criteria was termed "nonreactive." The presence or absence of periodic heart rate changes was assessed in all patients with spontaneous uterine contractions regardiess of the NST resuits. In patients with a nonreactive ;\JST and a quiescent uterus, contractions 0002-937817\J/061)590+04$00..!0/0


197\J The C. \'. Mosbv Co.

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were induced bv an intravenous infusion of a dilute oxytocin solution. A CST was termed "positive" if. m any 10 minute period. repetitive late decelerations were observt>d with two or more spontaneous uterine contractions or three oxytocin-induced uterine contractions. A CST was termed "negative" if. in any 10 minute period. late decelerations were absent with two or more spontaneous uterine contractions or three oxytocin-induced contractions and there was no positive window elsel\ here in the record. A CST that demonstrated intermittent late decelerations and no clearly positive or negatin' window was termed "equivocal." A positive or equivocal CST was considered falsely predictive if followed by labor that resulted in spontaneous vaginal delivery of a normal infant. Contraction stress tests that demonstrated either prolonged bradycardia or periodic changes other than late decelerations were termed "unclassified." FBM measurement. The presence or absence of FBl\Is was determined in 29 consecutive patients with abnormal CSTs. The interval between the CST and the FBM measurement ranged from 30 minutes to 6 hours. FBMs were assessed by a real-time B-scan method ~ADR Model 2130. Tempe. Arizona). Patients were studied in a semirecumbent position and not permitted to smoke during the observation period. A 3.5 MHz transducer was placed on the abdomen and a(ljusted such that a longitudinal scan of the fetus in either a coronal or sagittal plane was obtained. FBMs were defined as convergent chest wall movements \·l'ith abdominal excursion. Observations were recorded as FB.\1s present if there was at least one episode of FBM of 30 seconds or greater present during a 30 minute period. The results of these observations were not disdosed to the physicians managing the patients.

Results Positive CST. Fourteen patients with a positive CST were studied. All but one patient had a nonreactive NST. Indications f(H CST included hypertension (nine). diabetes (three), postdate (one), and systemic lupus ervthematosus (one). Gestational age ranged from 31 to 44 ·weeks (mean 38.9 ± 0.8 [SE~I] weeks). All were delivered within 36 hours of the CST. FBMs were present in 10 patients with a positive CST (Table I). T\vo were delivered by elective primary cesarean section (one for breech presentation and one with severe hypertension and an ''unfavorable" cervix). Labor was induced and an internal monitor was placed in eight patients. In seven of these eight, there were no consistent FHR patterns characteristic of fetal distress: five were delivered vaginally and two by cesarean section for failure of labor to progress. The remaining

FBMs and abnormal CST 591

Table I. FB\fs in 14 patients with a positive CST FBA1 present No. of patients Mode of delivery: Primary LSCS Labor and vaginal deliverv Labor an~l LSCS for fetal distress Labor and LSCS (other indication) Apgar srore: I min.

>7 7 7 7

Fetal breathing movements and the abnormal contraction stress test.

Papers of the Society for Gynecologic Investigation Fetal breathing movements and the abnormal contraction stress test F R A:\ K A. 1\f A I\ N I :\'...
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