The relationship between fetal heart rate accelerations, fetal movements, and uterine contractions

FETUS, PLACENTA, AND NEWBORN

The relationship between fetal heart rate accelerations, fetal movements, and uterine contractions E. Sadovsky, R. Rabinowitz, A. Freeman, and S. Yarkoni Jerusalem, Israel The association between fetal heart rate (FHA) accelerations and fetal movements during uterine contractions was studied in 52 pregnant women near term or at the beginning of labor. FHA and uterine contractions were recorded by tococardiograph . At the same time, fetal movements, whether associated or not with contractions, were viewed by real-time ultrasound. During uterine contractions, 95.5% of the FHA accelerations were associated with fetal movements. Also, 90.9% of the accelerations which appeared when the uterus was not contracting were associated with fetal movements. Fetal movements were not seen in 91% of uterine contractions which were not associated with FHA accelerations. The suggestion is made that uterine contractions stimulate both fetal movements and FHA accelerations. (AM. J. OBSTET. GYNECOL. 149:187, 1984.)

Fetal heart rate (FHR) accelerations that are accompanied by fetal movements are considered to be a good indication of fetal well-being.'· 2 Nonstress testing based on the occurrence of FHR accelerations associated with fetal movement during a certain period gained unprecedented popularity among obstetricians and perinatalogists.3 - 7 Timor-Tritsch et al. 8 showed that FHR acceleration appears at or near the onset of fetal movements. The nearly synchronous onset of fetal movements with the observed acceleration suggests a coordinated control of both of these functions; this control presumably arises in the fetal brain. The cortical nerve cells associated with motor function and those cells associated with cardiovascular function are anatomically in close proximity.8 Weingold et al. 9 separated FHR accelerations into two types. They defined as periodic those accelerations that occur in conjunction with uterine contractions, and suggested that they might be the result of partial occlusion of the umbilical vein during contractions. The more common, nonperiodic, accelerations are unrelated to contractions and are generally associated with fetal movements . Dawes et al. 10 showed that nearly all large FHR accel-

From the High Risk Pregnancy Unit, Department of Obstetrics and Gynecology, Hadassah University Hospital. Received for publication june 14, 1983; revised October 24, 1983; accepted November 30, 1983. Reprint requests: Dr. E. Sadovsky, P.O.B . 1200 IL 91 120, jerusalem, Israel.

!-

I 11 \1 \

·w.

f

"' IJ

:I i

~ ,..,

.

I

I·

.

• •

'

• t

I

I

00

I

f

I sl ~

i

~0

I

I

'

I

~ 1\

I

T

II I

ll'

I

I I

i

I

i

It

1

! t

.

- ~/

"'

.J

'

I

~~

IY' I'

i

r~

I

I

. aftl,o 1

•

~'o T

L

ItS* u:s•

t

!·

,Jo-t1

I I

;

I

1

- """"". .,.. I

.il J.U 'J ."I, f·J,

. .-1

.. II

I

~

'f

r

•••• n I

Jo 1

'~0

,.,.

,_...

1

8

I I

r

./~ .i.. tl .1'"'\ ..... ~~ I I~

-=:

Fig. 1. Relationship between FHR accelerations (four accelerations in upper tracing), uterine contractions (six contractions in lower tracing), and fetal movements (five groups of vertical lines in the lower tracing). Paper speed, 1 em/min.

erations were associated with movement of the fetal trunk. More recently , Rabinowitz et al. 11 confirmed that the large FHR accelerations in cases without uterine contractions were associated with fetal movements. No mention was made of whether the periodic accelerations which occur in conjunction with uterine contraction are also associated with fetal movements. It would not be unreasonable to expect that the same stimuli that affect fetal movements and nonperiodic 187

188 Sadovsky et al. Am.

May 15, 1984 Gynecol.

J. Obstet.

Table I. Association of FHR accelerations with uterine contractions and fetal movements With contractions Total No. of accelerations 199

No.

I

With fetal movements

Ill (55.8%)

I

Without contractions Without fetal movements

No.

5 (4.5%)

88 (44.2%)

106 (95.5%)

Table II. Relationship of uterine contractions without FHR accelerations to fetal movements Total No. of contractions

With fetal movements

Without fetal movements

144

13 (9%)

131 (91%)

heart rate accelerations also affect periodic accelerations. The purpose of this study was to explore, during periods of uterine contraction, the possible connection between FHR accelerations and fetal movements as viewed by real-time ultrasound.

I

With fetal movements 80 (90.9%)

I

Without fetal movements 8 (9.1%)

the distance between the edges of the two transducers was approximately 10 em. Fetal movements were defined as flexion or extension of limbs or trunk, or both, and were recorded as a line with a special marker by the observer on the bottom of the FHR monitor's running paper. As previously shown by Timor-Tritsch et al. 8 the onset of fetal movements usually occurred at the beginning of the contractions (Fig. 1). Movements that occurred within 6 seconds of each other were considered to be a single movement. The number of accelerations and their association with fetal movements and uterine contractions were noted on each chart. Statistical data were evaluated by the binominal test. Results

Material and methods

The study group was composed of 52 women-51 normal pregnancies and one case of mild preeclampsia. The gestational ages ranged from 34 to 42 weeks. All women had either Braxton Hicks contractions or premature uterine contractions or were in the beginning stage of labor with an average of 3. 7 contractions per 10 minutes. Many of these contractions were weak, not felt by the woman but recorded by the tococardiograph. None of the women had rupture of membranes. Women with poor perinatal outcome (perinatal death, fetal distress in labor, Apgar score lower than 7, intrauterine growth retardation) were excluded from the study group. The participants were studied while they were lying in a supine position in a quiet room, and blood pressure was measured to exclude supine hypotension. Fetal heart rate was monitored for 8 to 25 minutes (average, 13.3 minutes) by an external Doppler ultrasound system (Hewlett-Packard 8030A cardiotocograph) with the transducer directed at the fetal heart. FHR accelerations were defined as an increase in FHR of at least 15 bpm above the baseline, lasting 15 seconds or more. At the same time as the FHR was recorded, the uterine contractions were recorded by the external tocograph. Fetal movements were observed by means of a linear-array real-time B-scan method (Unirad, Sonofluoroscope lA). The real-time ultrasound transducer was placed on the maternal abdomen and directed at the fetal pelvis and small parts. To avoid interference,

Table I shows the FHR accelerations and their association with uterine contractions and fetal movements. Altogether, 199 accelerations were recorded in the 52 women. One hundred eleven of them (55.8%) were associated with uterine contractions, 106 of these were also associated with fetal movements (95.5%), and five (4.5%) were without fetal movements (p < 0.001). Eighty-eight of the accelerations (44.2%) were without uterine contractions, and 80 (90.9%) of these were associated with fetal movements, whereas fetal movements were not observed with eight (9.1 %) (p < 0.001). The rate of accelerations that were associated with fetal movements was independent of the existence or nonexistence of uterine contractions. The differences were not significant. Table II shows the relationship of uterine contractions not associated with FHR acceleration to fetal movements. In 131 contractions without accelerations, among 144 (91.0%), there were also no fetal movements, as compared to 13 (9.0%) contractions with fetal movements (p < 0.001). Mention should be made of the fact that 15 of 30 fetuses who had accelerations with contractions also had spontaneous fetal movements with accelerations. All fetuses who had accelerations with contractions also had accelerations with fetal movements. Comment

The results confirm the previous findings 10• 11 that usually FHR accelerations are associated with fetal movements. Possibly, the 13 accelerations without ob-

Volume 149 Number 2

served fetal movements actually might have occurred while the fetus moved its arms or a part of its upper body that was not viewed by ultrasound. Moreover, this study shows that acceleration associated with fetal movements can occur with or without uterine contractions. The fact that the fetus moves vigorously during uterine contractions, and that these movements coincide with FHR accelerations, was also previously shown by Pearson and Weaver. 12 According to Weingold et al. 9 the periodic FHR accelerations are associated with uterine contractions. Our results show that these periodic accelerations are also associated with fetal movements. Previous studies have shown that FHR accelerations associated with fetal movements can be stimulated by noise 13 • 14 and by external touch. 15 We suggest that uterine contractions stimulate both fetal movements and FHR accelerations. According to Weingold et al., 9 the contractions cause the benign type of periodic FHR accelerations by partial occlusion of the umbilical vein, which produces hypovolemia, hypotension, and increased FHR via the physiologic mechanism of baroreceptors. Possibly, the same mechanism stimulates the fetus to move.

REFERENCES l. Lee, C. Y., DiLoreto, P. C., and Logrand, B.: Fetal activity

acceleration determination for the evaluation of fetal reserve, Obstet. Gynecol. 48: 19, 1976. 2. Rochard, F., Schifrin, B.S., Goupil, F., et al.: Nonstressed fetal heart rate monitoring in the antepartum period, AM. j. 0BSTET. GYNECOL. 126:699, 1976. 3. Evertson, L. R., Gauthier, R. ]., Schifrin, B. S., et al.: Antepartum fetal heart rate testing. I. Evolution of the nonstress test, AM. J. 0BSTET. GYNECOL. 133:29, 1979.

FHA accelerations, fetal movements, and contractions

189

4. Gauthier, R. ]., Evertson, L. R., and Paul, R. H.: Antepartum fetal heart rate testing. II. Intrapartum fetal heart rate observation and neonatal outcome following a positive contraction stress test, AM. J. OBSTET. GYNECOL. 133:34, 1979. 5. Rayburn, W. F., Durhring, J. L., and Donaldson, M.: A study of fetal acceleration tests. AM. J. OBSTET. GYNECOL. 132:33, 1978. 6. Pratt, D., Diamond, F., Yen, H., et al.: Fetal stress and nonstress tests: An analysis and comparison of their ability to identify fetal outcome, Obstet. Gynecol. 54:419, 1979. 7. Keegan, K. A., and Paul, R. H.: Antepartum fetal heart rate testing. IV. The nonstress test as a primary approach, AM.]. 0BSTET. GYNECOL. 136:75, 1980. 8. Timor-Tritsch, I. E., Dierker, L.J., Zandor, I., eta!.: Fetal movements associated with fetal heart rate accelerations and decelerations, AM. J. OBSTET. GYNECOL. 131:276, 1978. 9. Weingold, A. B., Yonekura, M. L., and O'Kieffe, J.: Nons tress testing, AM. J. OBSTET. GYNECOL. 138: 195, 1980. 10. Dawes, G. S., Wisser, G. H. A., Goodman,]. D. S., and Levine, D. H.: Numerical analysis of human fetal heart rate: Modulation by breathing and movement, AM. ]. 0BSTET. GYNECOL. 140:535, 1981. 11. Rabinowitz, R., Persitz, E., and Sadovsky, E.: The relation between fetal heart rate accelerations and fetal movements, Obstet. Gynecol. 61: 16, 1983. 12. Pearson, J. F., and Weaver, J. B.: A six-point scoring system for antenatal cardiotocographs, Br. J. Obstet. Gynaecol. 85:321, 1978. 13. Grimwade, J. C., Walker, D. W., Bartlett, M., et al.: Human fetal heart rate change and movement in response to sound and vibration, AM. J. 0BSTET. GYNECOL. 109:86, 1971. 14. Walker, D., Grimwade, J., and Wood, C.: Intrauterine noise: A component of the fetal environment. AM. J. 0BSTET. GYNECOL. 109:91, 1971. 15. Ron, M., Yaffe, H., and Sadovsky, E.: Fetal heart response to amniocentesis in cases of decreased fetal movements, Obstet. Gynecol. 48:456, 1976.