"l\tlixed cord compression," fetal heart rate pattein, and its relation to abnoimal cord position JOHN W. GOLDKRAND, M.D. JAMES P. SPEICHINGER, M.D. Omaha, Nebraska A total of 122 consecutive patients were electronicaiiy monitored in labor. The purpose was to relate a variable acceleration-acceleration:variable deceleration ("mixed cord compression") pattern to umbilical cord compression by comparing the monitor patterns to abnormal cord positions, length, or presentation as noted at delivery. Standard, accepted J,fi.nitinn.r nf fetal heart rate l!atterns were used in addition to this combined Pattern. Thirty-four (27.9 p;r cent) bdbies had abnormal cord positions. Of the 34, 28 .(82.4 per cent) of these cords were in patients with variable decelerations or the mixed acceleration: variable deceleration pattern; 19 of the 28 (67.8 per cent) showed the mixed pattern and nine (32.3 per cent) were variable decelerations. Accelerations alone had the same incidence of abnormal cord positions as normal monitor records. Literature review on the dynamics of umbilical cord compression and speculation on the results, as they relate to cord cornpression, are included.

tiona! experimental evidence has come from Towell and Salvador11 and others 1 "· 1 " that cord compromise may present itself in several different FHR patterns, depending on the hemodynamic changes incurred by the amount and type of umbilical cord compression. This study was initiated to evaluate FHR patterns, besides variable decelerations, which may relate to umbilical cord compression. Because of inability to observe the intrauterine environment during labor and document cord compression, an attempt was made to correlate the position of the cord at delivery to the FHR pattern and then perhaps extrapolate this back to the Intrauterine situation.

FETAL HEART RATE (FHR) patterns,asthey apply to clinical utilization of electronic fetal monitoring, have been well defined by Hon. 1 With clinical fetal monitoring now moving out of the university centers and into community hospitals,2- 4 FHR patterns that deviate from the accepted definitions may lead to confusion. Variable deceleration, as an indicator of some eiement of umbiiicai cord compromise, was first seen in goats by Bancroft. 5 The work of other men 1 • -'· " has further confirmed this assumption and given additional meaning to it. This type of cord compromise is estimated to occur in about one-third of all labors, based on blood-gas and acid-base studies of James and associates. 7 Acceleration and mixed acceleration: variable deceleration patterns 8 - 11 are being observed and discussed as to how they relate to fetal compromise. Addi-

Materials and methods Patients. Patients were collected consecutively from Jan. 1, 1974, to Feb. 28, 1974, from both the clinic and private service. During this interval, 164 patients were delivered of infants and 122 (74.4 per cent) were monitored. The criterion for fetal monitoring was a fetomaternal unit in labor. An additional 11 patients out of this population had either an elective repeat cesarean section or a primary cesarean section with less than one hour of labor in the hospital and were not monitored. Therefore, 31

From the Department of Obstetrics and Gynecology, University of Nebraska Medical Center. The Annual Prize Award Paper, presented at the Forty-second Annual Meetinl! of the Central Association of Obstetricians ~nd Gynecologists, New Orleans, Louisiana, October 3-5, 1974. Reprint requests: Dr. fohn W. Goldkrand, Department of Obstetrics and Gynecology, University of Nebraska Medical Center, Omaha, Nebraska 68105.

144

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FHR patterns and umbilical cord compression

145

Fig. 1. FHR acceleration pattern.

patients ( 18.9 per cent) delivered with labor but without fetal monitoring, and this was due to the temporary nonavailability of monitoring equipment. Of the 122 patients studied, 113 were delivered vaginally and nine by cesarean section. Equipment. Continuous electronic fetal monitoring was accomplished with either ( 1) a HewlettPackard 8020A Cardiotocograph with the l5180A Ultrasound amplifier adaptor or ( 2) a Corornetrics 1OIB Fetal Monitor. Monitoring was performed by both direct and indirect methods or an intermixing of the two. Indirect recordings of FHR utilized an ultrasonic probe, whereas the direct FHR was monitored by spiral electrode. Uterine contractions were indirectiy recorded by tocodynamometer and directly via a water-filled transcervical intra-amniotic catheter. The mode of fetal monitoring was dictated by the quality of the record or the information required in the given clinical situation. Evaluation of the fetal monitor records. The monitor tracings were read in their entirety in a retrospective manner without prior knowledge of the clinical situation. This ;vas later correlated. The interpretation was based on what were considered to be the predominant patterns throughout the labor. The interpretation of the fetal patterns was performed according to the method of Hon. 1 Additional patterns involved here are ( 1) pure accelt>rations of the FHR, occurring at any time irrespective of uterine contractions and with accelera-

Fig. 2. "Mixed cord compression pattern": Combined FHR pattern of variable acceleration:variable deceleration.

tion of greater than 15 beats per minute (Fig. 1) , and ( 2 ) accelerations and variable deceleratiOn ; these accelerations were occurring either independently with respect to the decelerations or immediately preceding the deceleration. This pattern involving variable accelerations and accelerations with variable decelerations will be referred to as

l\-iay 15, i 975 Am.]. Obstet. Gynecol.

'/6

70 60

-......... ~

v

so

177:'7.1 N••ller tf p1tle1ts II •o•ltor p1tt1r1 lfiiP ~ co•p•rt• to tilt total pep•l•tlll ...,, N=122 Nlllller of

60.7'7.

,.tt.. ts 11 •11ltor p1tt1r1 lrDIP

c:J wltll 1111ol'lltll ror• posltltl co•p•rtd to all •••ll•rs of tllat tro•p

40 M

20 10

NOIIAl PlTTEIN Fig. 3. Predominant FHR monitor patterns and the distribution of abnormai cord position in relation to the type of pattern.

1001 80

70

...:z... :: ... v

60

..I

N=34

90

82.4%

n

l

50

N=28

60

..... z

so

...•...

40

~

30

30

20 i1.87.

101

El

NORMAL PATTERN

5.8%

IM=21 ACCEl. ONlY

II

YARIAilf + MIXED PATTERN

Fig. 4. FHR pattern of patients with abnormal cord position.

the "mixed cord compression pattern" (Fig. 2). Excluded from this group are the secon1.ary accelerations or overshoot which may occur immediately following a variable deceleration. 9 Cord presentation or position. At the time of delivery, the position of the cord was evaluated. ~.J" uchal coids, cords less than 50 cn1. or of excessive length, and umbilical cord entanglement, impingement, or prolapse \A/ere noted.

Results Monitor pattern; cord position. There were 122 babies monitored during this study. Thirty-four (27.9 per cent) babies were delivered who were

10

~ 32.2%

I

n II 67.8%

70

40

20

M=U

~I I

YARIAIU DECEL.

N=19

I

MIXED CORD COMPRESSION

Fig. 5. Comparison of abnormal cord position in patients with variable deceleration or the mixed cord compression pattern.

considered to have an abnormal presentation of the umbilical cord. Fig. 3 presents an analysis of the monitor patterns seen and how they related to abnormal cord position. In patients with the normal pattern (including early head compression deceleration) , 13.8 per cent of the group had abnormal cord position, whereas 14.3 per cent of the patients with only FHR accelerations had any abnormality. ~Io patient \v.ith late decelerations had demonstrable cord problems. As expected, 36 per cent of the group with variable decelerations revealed abnormal cord position and, if one combines variable deceleration patterns with the mixed cord compression pattern, there is a 37.8 per cent incidence. In

Volume 122 Number2

FHR patterns and umbilical cord compression 147

1'77771 M••lter wit~ eac~ pattern coMpared ~ to th total •••Iter of patitlts N=l22

so

... ...~

40

1!5

30

A.

20

D

N••ber of altaorMal cords coMpared total u•lter in eac~ gro1p

wit~ ~.

39.1%

38.5%

10

PROGRESSION ACCEL. TO YAll ABLE DECEL. (A)

ACCEL. + VARIABLE DECEL. (8)

A+ 8

Fig. 6. Division of patients according to FHR pattern preceding the mixed cord compression pattern and the relation to the total population.

Fig. 4 the number of abnormal cord pos1t10ns in each group is compared to the total population with abnormal cord position. Here, 82.4 per cent of abnormal cords are found in patients with fetal monitor tracings of variable deceleration or the mixed cord compression pattern. The normal and purely acceleration pattern represent only a small group of abnormal cords. Seventy-four patients showed the variable deceleration or mixed cord compression monitor pattern. Of these, 28 (37.8 per cent) had an abnormal cord position. When one compares the number of patients with abnormal cord position to a variable deceleration or mixed cord compression pattern (Fig. 5) one finds 32.2 per cent with variable decelerations only and 67.8 per cent with the combined pattern. The mixed cord compression pattern group was subdivided into ( 1) a pattern initiated by accelerations and then progressing to variable decelerations and (2) intermixture of accelerations and variable deceleration. As this relates to umbilical cord compromise (Fig. 6), there seems to be no difference between the subgroups, both showing a 38 to 39 per cent incidence. Fetal outcome. Nine cesarean sections were performed: three for fetal distress and six for cephalopelvic disproportion or malpresentation. Of those with fetal distress, all were associated with late decelerations and none had an abnormal cord position demonstrated. Of the 122 babies delivered, 12 had a 1 minute Apgar score of less than 7 (Table I) ; five of these

Table I. Twelve of 122 infants with Apgar score of less than 7 at 1 minute Cord position Abnormal

Normal

I

I

Patient Apgar score No. 1 min. 5 min.

I

21 37

5 6

8 9

62

6

8

73 84

3 6

7 9

3 12 49

6 6 5

8 6 6

50

90

6 2

8 7

114

5

8

115

6

8

I Comment Short cord 40 em.

20 per cent abruptio present Cord nuchal x 1, arm x 1 ?/36 wk., 4 lb. 4 oz. 30 wk., 3 lb. 40 wk., cesarean section; cephaiope1vic disproportion Postmature 5 lb. 14 oz. 40 wk., 7 lb. 3 oz., precipitous labor

12 babies were in the group with an abnormally positioned cord. One baby in this series, born at 26 weeks after premature rupture of the membranes, with Apgar scores of 7 and 8, weighed 5 pounds and 14 oz. and died with disseminated herpes infection. Anesthesia and reiation to cord posiiion and outcome. The use of anesthesia was dictated by the clinical situation and usual practice in our hospital. Conduction anesthesia was predominant (80 patients, 65.6 per cent). Thirty~nine (32.8 per cent)

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Table II. Am·sthetic distribution in patients with abnormal cord position

Total population, N =- l 22

8 6.6%

Abnormal cord position, N = 34

41 33.6'/c 14

41.2%

had continuous epidural and 41 ( 33.6 per cent) spinal (all but one was saddle block) . Eight ( 6.6 per cent) patients had general anesthesia (sodium pentobarbital, nitrous oxide, oxygen, and succinylcholine) and all were delivered by cesarean section. There were 25 (28.1 per cent) pudendal blocks and seven ( 5. 7 per cent) local infiltration. Only two patients received no anesthesia, due to a rapid second stage of labor. The anesthesic distribution in the patients with an abnormal cord position is seen in Table II. Four of five babies with a 1 minute Apgar score of 7 had saddle-block anesthesia and one had conduction anesthesia. Among the seven babies with an Apgar score of 7 at 1 minute, but with a normal cord position, there were two saddle blocks, two pudendal blocks, one epidural anesthesia, and two general anesthetics. Comment

Multiple observers, beginning with Bancroft," have shown that complete occlusion of the umbilical cord causes prompt decrease in fetal heart rate, called a variable deceleration in its relationship to uterine contractions. That cord compression operates through the vagus nerve to cause deceleration has been shown by obliterating the effect with atropine. However, other vagally mediated responses may be operative to produce the same FHR effect. 1 The problem of partial occlusion has led to more varied results. Acidosis, at first respiratory and then metabolic, begins promptly and increases with the duration of complete occlusion. With partial cord compression, fetoplacental circulation is not totally stopped. Po 2 in the umbilical vein can maintain itself longer than in the artery. 7 Umbilical vein occlusion, however, which would occur before the artery in partial occlusion, causes the fetus to becon1e hypovoiernic and to respond with a heart rate acceleration 9 • 11 • 13 instead of a deceleration, which wil] occur as acidosis intervenes or occlusion be=

comes more complete. The Poseiro effect, with its reduction in maternal blood pressure and hypo-

Pudendal

Local

l\ one

25 28.7% 8 23.5%

7 5.7%

; 6' ~

2

5.9%

----------

perfusion of the uterus, is another possible reason for fetal heart changes that may mimic cord compression. tz The data presented in Figs. 3 and 4 relate the abnormal cords found at delivery to the FHR patterns, as was anticipated. That all abnormally placed cords do not have an abnormal monitor pattern is also shown. As one would expect, malpositioning of the umbilical cord cannot always be equated with cord compression or compromise. The converse may also be applicable: that monitor patterns suggestive of cord compression occur by entanglement, impingement, abnormal length, or other vagal features which cannot be realized at the time of delivery. This is evident in Fig. 3, where only little more than 30 per cent of patterns (where suspected compression should have occurred) had evidence of abnormally positioned cords. From this group of patients, only 11 per cent had pure acceleration patterns (Fig. 1) and their percentage of abnormal cord presentation was the same as in those patients with normal monitor patterns. However, based on the speculation of Hon 1 and O'Gureck, Roux, and Neuman, 14 we have not ruled out that this pattern may be either of premonitory significance or evidence of very mild cord compression in utero: vis-a-vis partial cord occlusion. \Nhen one now looks at the variable decelerations and the mixed cord compression pattern, as we are calling the variable acceleration--acceleration: variable deceleration pattern, we see the majority of abnormal cord positions (Fig. 2). In fact, the mixed cord compression pattern was associated with twice as many abnormal cords as the pure variable deceleration pattern (Fig. 5). When the acceleration preceded or was accompanied by variable deceleration, there were no significant differences in relation to the cord condition at birth (Fig. 6). From these observations of the high incidence of abnormal cords with FHR patterns suggesting cord compression, we would like to speculate that this group with the mixed cord compression pattern had n1ore

Volume 122 Number 2

FHR patterns and umbilical cord compression

149

1'777,:11 ll••lter of potlo1ts i1 •••itor patter• trotp

~ co•portd to tilt total pop ..

70

0

•ti•• wltert 11=186

ll••lltr of patiuts i• •••itor patter• ''''' witll all•or•al cor• positio1 to all •••lltrs of tkat gro1p

co•p•re•

62.4% 60

....

!

. ~

so 40

30 20 10

RGIIAll PATTERN

ViiiliU

ViiiliU DiCiL. + MIXED PATTEIII

DECEL.

Fig. 7. Combined data: Predominant FHR monitor patterns and the distribution of abnormal cord position in relation to the type of pattern.

90

80

...z ...... 1-

v

1

i

N=49

83.7%

80

70

70 •

60

60

50

so

40

IIC

N=41

40

20

16.3%

10

N=8

NORMAL PATTERN

N=41

65.9%

34.1%

N=27

30 20

30 -

1 1

N=14

10

VARIABLE DECEL. YARIAILE DECEL. + MIXED PATTERN

Fig. 8. Combined data: FHR pattern of patients with abnormal cord position.

in utero cord compression of varying degrees than the other groups. Yet, the absence of fetal distress on the monitor, as defined by Hon 1 for cord compression, may lead one to further speculate that the mixed cord compression pattern is more often as'ociated \vith only partial cord occlusion than is the pure variable deceleration. Anesthetic modalities were distributed in relati\·ely the same manner among the group with abnormal cord positions and the population as a

MIXED CORD COMPRESSION

Fig. 9. Combined data: Comparison of abnormal cord position in patients with variable deceleration or the mixed cord compression pattern.

whole and thus appeared to have no eflect on the observed monitor patterns as done in this study. This study has investigated a combined type of feta! heart rate pattern involving accelerations and variable decelerations. The data suggest that this pattc·rn is associated ,,·ith more abnormal cords found at delivery and questionably more intrauterine partial cord compression. Whether thi:; mixed cord compression pattern sef'n in the clinical setting wili progress to fetai distress is unknown.

Am. J, Obs · · (

However. these obsen·ations and speculations about the mixed cord compression pattern help to identify a monitor tracing that deyiates from the accepted and established pure FHR patterns.

Addendum Six months after the initial analysis, another 64 consecutively monitored patients were studied. The monitor records were read by the same persons and the same criteria were utilized. Seventeen of the 64 ( 26.6 per cent) patients had abnormal cord position at the time of delivery. The relation of the monitor pattern to cord position is shown in Table III. Of the 17 patients with abnor1nai cord posttlon, four ( 235 per cent) had a normal monitor pattern and 13 ( 76.5 per cent) demonstrated variable deceleration and the mixed cord compression pattern. Five ( 38.5 per cent) of these 13 with an abnormal monitor pattern showed variable deceleration and eight ( 61.5 per cent) had the mixed cord pattern alone.

'>OW< ,[

Table III. Relation of monitor pattern to cord Jl'''ition (N = 64) Total no.

Pattern

of patients

Normal Variable deceleration Variable deceleration + mixed pattern

22 (34.4%) 24 (37.5%) 42 (65.6%)

Abnormal ,~~ .1.'\ro.VUAJ

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Neonatal depression and fetal heart rate patterns during labor, Obstet. Gynecol. 30: 347, 1972.

"Mixed cord compression," fetal heart rate pattern, and its relation to abnormal cordposition.

"l\tlixed cord compression," fetal heart rate pattein, and its relation to abnoimal cord position JOHN W. GOLDKRAND, M.D. JAMES P. SPEICHINGER, M.D. O...
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