Fetal breathing movements and the nonstress test in high-risk pregnancies FRANK

A.

LAWRENCE LOUISmE KIRK

MANNING, D.

PLATT,

SIPOS, A.

Los Azgeles,

M.D. M.D.

R.N.

KEEGAN,

JR.,

M.D.

Calijornia

Three hulndred ninety-eight observations of fetal breathing movements (FBM) and the nonstress test (NST) were made in 223 patients. The presence of FBM was noted in a significantly higher proportion of tests with a reactive NST (88%) than a nonreactive NST (67%). Conversely, a significantly higher proportion of tests were reactive when FBM were present (82.6%) than when FBM werje absent (49%). A significant relationship existed between either test and the outcome of pregnancy as judged by the five-minute Apgar score or the incidence of fetal distress in labor. Combining two normal tests did not improve the accuracy in predicting outcome; but the combinatoon of both tests, when abnormal, produced a significant improvement in predicting fetuses likely to heave an abnormal outcome. The combination of the normal with the abnormal test had a predictive accuracy similar to a single normal test in predicting a normal five-minute Apgar. This combination was associated with an incidence of fetal distress in labor intermediate between that seen with either the normal or abnormal test when alone. Neither a single test nor the combination of tests as helpful in identifying the small-for-gestational age (SGA) infants. These data indicate antepartuim fetal evaluation may be improved when more than one biophysical variable is used. (AM. J. O~BSTET. GYNECOL. 135:511, 1979.)

A N A L Y s I s of fetal biophysical variables holds promise as a means of antepartum fetal assessment. Both the association of acceleration of the fetal heart rate with fetal movements (the nonstress test or NST) and the presence of fetal breathing movements (FBM) have been shown in independent studies to be helpful in differentiating the normal from the compromised fetus.‘-” With either test the accuracy is greatest in predicting the normal fetus. Neither test is as accurate in identifying the compromised fetus. From the Depart.ment of Obstetriu and Gpecolog. University of Southern Calijo&a Sclwol of Medicine, and Women’s Hospital, Los Angeles CouxtplJniversity Southem California Medical Center. Supported by a grant from the National Foundation-March of Dimes awarded Manning, M.D. J Received for publication Revised

December

Accepted December

October

to Frank

of

A

13, 1978.

14, 1978.

Methods

28, 1978.

Rep% requests: Dr. Frank A. Manning, M.D., Women’s Hospital, .Room 5K-9, Los Angeles County -University of Southern California Medical Center, 1240 North Mission Rd., Los Angeles, California 90033. 0002.9378/79/200511+05!~00.50/0

Biophysical biorhythms have been demonstrated in animal fetuses and recently in the human fetus.j-’ Both the incidence and character of FBM are related to the sleep state of the fetus.6 Thus, whereas the presence of FBM appears to be a reliable index of fetal well-being, it is hot possible, in a single observation, to determine if the absence of FBM reflects a sleep state or compromise. The relationship of the NST to fetal sleep states is unknown. The similarities of the NST to FBM are striking in that a reactive pattern (normal) NST is an accurate index of Fetal well-being whereas a nonreactive pattern (abnormal) NST is a poor index of fetal compromise.* This study was designed to evaluate the relationship of two fetal biophysical variables, the NST and FBM, to compare the independent predictive accuracy of each test, and to determine if the combination of both tests can improve predictive accuracy.

0

1979

The

C. V. Mosby

Co.

Patients studied were selected at random from the high-risk pregnancies referred for antepartum fetal heart rate testing at Women’s Hospital, LACiUSC 511

Table

I. Srudy population

Post date (>42 Diabetic Class A (7) Class B (46)

weeks)

Class C (9) Class D (6) Class F (2) Siypertensive disease Suspected intrauterine growth retardation Kh isoimmunized pregnancy FJ,emoglobinopathies (SS, SC) Maternal medical disorders Total

76 70

26

18 10 5 18 m

SPedical C&W-. The NST M~S performed using a method previously described.” An NST was termed a reactive pattern (R) or normal if, during a 20 minute period, there were two or more fetal heart rate accelerations of 15 bpm or greater of at least 30 seconds duration associated with fetal movement. The NST was termed a nonreactive pattern (NR) or abnormal if there were less than two accelerations of the fetal heart Ivith fetal movement in a 40 minute period.” The resuits of the SST were used in clinical management. Fetal breathing movements were recorded by means of a real time B-mode ultrasound method (ADR Mode! 2130).” FBM were defined as convergent chest wail movements in conjunction with abdominal wall excursions. FBM were observed immediately before, during. or after the NST. The majority of observations were made immediately after the NST. Patients were scanned until either a period of FBM of 30 seconds or greater was observed or 30 minutes elapsed.” FBti were recorded as either present or absent. The results of FBM observation were not disclosed and hence did not influence clinical management. The results of the NST. FBM, and combined NSTi FBM were correlated with the outcome of pregnancy as reflected by the five-minute Apgar score, the incidence of fetal distress in labor, birth weight, and meconium staining of amniotic fluid. Fetal distress was defined as any abnormal intrapartum fetal heart rate pattern that precipitated emergency delivery of a fetus regardless of the condition of the fetus at delivery. Fetal heart rate patterns considered indicative of fetal distress included repetitive late decelerations, intermittent late decelerations with loss of heart rate variability, unremitting se\-ere variable decelerations, or persistent fetal brady-cardia. infants were considered small for dates if the birth weight was less than the tenth percentile for gestational age and sex.

Three hundred rrinety-eight obser%,c:ions 3f FBM and the NST were made in 223 patients (Table i)~ Most patients delivered within one week of the last test (86%) and all delivered within three weeks. Overall, FBM were present in 83.7% of observations and the NST was reactive in 78.4% (Table II). FBM were present in 88% of observations when the NST was reactive as compared to 67% when the NST wa6 nonreactive (p < 0.05). Conversely: the NST was rcaciive in 82.6% of observations when FBM were present and reactive in 56.9% of observations when FBM were absent (p < 0.05). FBM,

NST,

and

five-minute

Apgar

(,TabXe

III).

A

normal five-minute A.pgar score (~7’) was observed in 179 of 187 patients (95.7%) with FBM present on the last observation before delivery and in 27 of 36 patients (75%) with FBM absent (p < 0.05). One hundred sixty-one of 169 patients (95.2%) with a reactive NST on the last obsenJation delivered an infant with a normai five-minute Apgar score as corAlpared to 15 of 54 (83.3%) with a nonreactive NST (p < 0.03). The predictive accuracy of the NST and FBM was not significantly different. A normal five-minute Apgar score was observed in l46 of 151 patients (96.7%) when both the NST was reactive and FBM were present in the :ast observation before delivery. The predictive accuracy of two normal tests offered no significant improvement over that of either normal test alone. Thirty-five of 36 patients (97.2%) with a nonreactive NST but with FBM present on the last observation delivered an infant with a normal five-minute Apgar score. The predictive accuracy of this combination was similar to that of the presence of FBM alone (96%) but significantlv different from the predictive accuracy of the nonreaciive NST (83.3%) when considered alone (p < 0.05). Seventeen of 18 patients (94.4%) with a reactive NST but with FEM absent on the last observation delivered an infant with a normal five-minute Apgar score. The predictive accuracy of this combination was similar to that of a reactive NST alone (95.2%) but significantly different from the predictive accuracy of the absence of FBM (75%) (p < 0.05). Finally, 8 of 18 patients (44.3%) with both a nonreactive NST and absent FBM on the last observation delivered infants with abnormal five-minute Apgar scores (

Fetal breathing movements and the nonstress test in high-risk pregnancies.

Fetal breathing movements and the nonstress test in high-risk pregnancies FRANK A. LAWRENCE LOUISmE KIRK MANNING, D. PLATT, SIPOS, A. Los Azgele...
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