Fetal heart patterns and their clinical interpretation This text of fetal monitoring was prepared for Sonicaid Limited by Professor R. W. Beard, M. D., F. R.C.O.G., Department of Obstetrics & Gynaecology, St Mary's Hospital, London W2. assisted by T. S. Finnegan, B.Sc., Technical Director, Sonicaid Limited, Bognor Regis, Sussex.

Special thanks are due to the Obstetric and Nursing Staff at St Mary's Hospital (Praed Street) and in particular to Dr Philip Steer, Dr David Little and Miss Cynthia Knight for their assistance in the preparation of this book.

Editor's Note : All of the tracings contained in this publication were recorded at a speed of 1 cm/minute unless otherwise noted.

C Copyright 1974 Sonicaid Limited

Page 3 I NTRODUCTION Principles of Fetal Monitoring Monitoring Techniques

8 I NTERPRETATION OF THE CONTINUOUS FHR TRACE Nomenclature Significance of FH R traces relative to pH

12 I LLUSTRATIVE FHR TRACES Normal Baseline Bradycardia Baseline Tachycardia Acceleration Early Deceleration Variable Deceleration Late Deceleration Loss of beat-to-beat variation

30 UTERINE CONTRACTIONS Normal Abnormal

34 RECORDING ARTEFACTS

38 CASE HISTORIES Patterns occuring at full dilatation Recovery following acute asphyxia Epidural 'top-up' Effects of drugs Uterine hyperstimulation Loss of beat-to-beat variation Effect of posture 'Bedpan effect'

55 APPENDIX Technical Aspects of Monitoring

57 REFERENCES I 0 •

• ___ o. a 1?QNICAKJI //' FETAl. MONITOR M01*L FM2 Principles of Fetal Monitoring For any obstetrician who is new to fetal monitoring, it is important to understand from the outset that the continuous fetal heart rate monitor is not simply a sophisticated form of fetal stethoscope. Intermittent record- ng of the fetal heart rate (FHR) with a fetal stethoscope is still the most commonly used method for monitoring the condition of the fetus in labour. Observations are usually made every 15 to 30 minutes between contractions, and slowing of the heart rate is generally considered to be evidence of fetal asphyxia. The monitor also records the FH R, but since it is able to do this continually, the rate is measured both between and during contractions, thus providing a great deal more information about the condition of the fetus than the intermittent record. This continuous record requires careful study, and therefore cannot be interpreted in the same manner as the intermittent observations made with a fetal stethoscope. The principle underlying the detection of fetal asphyxia in labour by continuous FH R monitoring is that the uterine contractions are a form of stress to the fetus, which is followed by a period of recovery between contractions. With each contraction there is a temporary reduction in the blood flow to the placenta which is of little consequence to the fetus if it swell oxygenated. If, on the other hand, placental function is compromis- ed in some way, the fetus becomes temporarily asphyxiated with each contraction accompanied by some abnormality in the FHR. Initially the FHR abnormality is confined to the contraction phase but, in time, extends into the period of recovery between contractions.

The interpretation of the FHR trace is complicated by the fact that alterations in the FH R which seem to be abnormal may appear for causes other than asphyxia. This can happen, for example, during the second stage when the fetal head is being compressed as it descends in the pelvis, resulting in deep decelerations of the FHR similar to those seen during asphyxia. Clearly if all FHR decelerations were regarded as evidence of asphyxia quite a few babies would be delivered unnecessarily by Caesarean section. For these reasons it is recommended that the technique of fetal blood sampling for pH determination should be instituted in conjunction with continuous FHR monitoring, to make the diagnosis more definite. Although we do not know precisely at what point tissue damage occurs n the asphyxial process it seems unlikely that the fetus will be in any danger if the scalp blood pH is above 7 25. It is hoped that the description of FHR monitoring which follows will serve as an introduction to the subject for obstetricians and midwives unfamiliar with monitoring. It is in no way a substitute for the knowledge that can only be gained by long and continuous use of monitoring on the labour ward. Monitoring Techniques - Measurement of FHR

Both internal and external methods for determining the FHR and uterine contractions are available, the selection of either technique being mainly dependent upon clinical circumstances. In either case of FHR measure- ment the instantaneous beat-to-beat rate is computed by measuring the nterval between paired beats and then converting this measurement by a card iotachometer into the equivalent rate in beats per minute.

Internal method - A unipolar electrode screw or clip is attached to the fetal scalp (or buttocks if a breech presents). This picks up the fetal FOG, with a separate electrode in contact with the vagina of the mother acting as the other pole. The cardiotachometer is triggered by the R-wave of the fetal ECG and provides a recording of instantaneous FHR which is essentially free of errors caused by external factors. This method is therefore considered to give a more precise recording than that given by the external method.

External method- The external method is valuable when it is not possible to use an internal method, as for example when the cervix is tightly closed, or in the case of the second twin, (Steer & Beard, 1973). Movements of the fetal heart are detected by a beam of acoustic energy transmitted by a transducer attached to the mother's abdomen. Because of the shape and arrangement of the multi-elements on the transducer head, a wide angle of emitted sound can be achieved which allows a certain amount of fetal movement without loss of signal. The cardio- tachometer is triggered by a signal thought to originate from movement of the heart wall, and therefore provides a recording of FHR which derives from the mechanical activity of the fetal heart. This is a different parameter from that measured by the internal method, since the ECG record is derived from the electrical activity of the heart. The external records have different characteristics which make the beat-to-beat variation of the FH R more difficult to interpret, and at the time of writing the relevance of this beat-to-beat variation has not yet been so fully evaluated as it has been from the measurement by FOG.

Steer, P. J. and Beard, R. W. (1973). Two cases of continuous fetal heart rate monitor- I ng in twins. Brit. Med. J., 3, 263.

4 Screw electrode Clip electrode

External monitoring transducer Monitoring Techniques - Measurement of Uterine Contractions

Internal method - A pressure transducer and a long polythene catheter filled with sterile saline are used for this purpose. The catheter is fed through the cervix by means of an introducer so that the tip comes to lie behind the head of the baby. The catheter is mostly used when the membranes are ruptured, but with care it can be inserted extra- amniotically without rupturing the membranes, For technical reasons this method of recording uterine contractions is generally not used in clinical practice, except when it is important to know what the intra- uterine pressure is, as for example, if syntocinon is being used in a woman who has had a Caesarean section in a previous pregnancy. However, it is a method with which all who are involved in monitoring should be familiar.

External method-A tocodynamometer of the 'guard-ring' type is used for this purpose. It is applied to the mother's abdomen near the fundus and responds to the forward displacement of the uterus as it contracts. It is important to understand that, while recording the duration and frequency of contractions, it does not provide an absolute measurement of basal or peak uterine pressure. However, it does provide a record of the frequency and duration of contractions, and because of the ease of application of the transducer the external method is most widely used in clinical practice. Pressure transducer and catheter

- -s

External tocodynamometer Nomenclature

It is necessary to agree on a nomenclature for describing an FH R trace which will be clear to all members of the medical and nursing staff on a labour ward. One of the earliest workers in the field, Caldeyro-Barcia, made an important contribution to monitoring when he divided the slowing of the FHR during contractions into Type 1 and Type 2 dips. This description is used widely throughout the world but has the limitation of only characterising the timing of the deceleration without providing information on the amplitude or duration. In addition, practical experience has shown that considerable confusion exists as to exactly what the distinction is between Type 1 and Type 2 dips. These difficulties have given rise to the following nomenclature used in this publication which is a modification of that proposed by Hon (1963, 1968), and which has the advantage of describing in simpleterms all the significant characteristics of the FH R trace.

Definition of terms - see F I g u re 1. Baseline FHR -the rate between contractions Deceleration-the slowing of the FHR during a contraction. f the FH R increases during a contraction, this is referred to as an Acceleration'. Lag-time - the time that elapses between the peak of a contraction and the lowest point of a deceleration. Beat-to-beat variation - a term used to describe the variation in the FH R that is observed on the trace. It is a rather non-specific term which includes FH R variations that are not strictly 'beat-to-beat' having a longer time base. The term has the advantage of being easily understood and has been retained until a more precise method of quantitating FH R variability has evolved.

Basal tone-the resting pressure within the uterus between contractions. It can only be determined by internal methods of pressure measurement. Peak pressure-the maximum intrauterine pressure achieved during a contraction. Again an internal method must be used to measure it. Frequency of contractions- usually expressed as the number of contractions occurring over a 10 minute period, e.g. normally 3 or 4 in 10. Duration of a contraction-the interval between the time when the uterus is first observed to contract, to when the pressure has returned to the resting level.

Hon, E. H. (1963). The classification of fetal heart rate, I. A working classification. Obstetrics & Gynaecology, 22,137. Hon, E. H. (1968). An atlas of fetal heart rate patterns. Harty Press Inc., New Haven, Connecticut.

Deceleration -.---Duration -----s 160

FETAL Baseline rate HEART RATE 140 (beats/mm) : -Deceleration Amplitude 120 135- I FHR 130 \Loss ofbeat Lag- 125 to beat time Normal variatiqn

UTERINE CONTRACTION - Peak pressure

I Basal tone

Duration

I I

TERMS USED IN THE STUDY OF CONTINUOUS RECORDS OF FHR

Figure 1 Significance of FHR traces relative to pH

As yet there is no generally agreed reference point against which the significance of FHR patterns can be assessed; what is needed is a reliable index of the effect that asphyxia is having on the condition of the fetus. Damage to fetal tissues will not occur until the tissues are so depleted of oxygen that lactic acid starts to accumulate. This being so, then the fetus is not in danger as long as its pH is maintained, whereas a fall in pH is evidence of significant asphyxia, particularly if this fall is progressive.

A comparison of FHR patterns against pH is presented in Figure 2 from Beard et a! (1971). This shows that, although certain continuous FHR abnormalities are associated with a higher incidence of acidosis than others, there is still a considerable overlap. Even the worst pattern (complicated tachycardia) has only a 53% incidence of fetal acidosis (pH X7 25), and this underlines the need to use pH determinations as an adjunct to FH R monitoring, for neither tells the whole story on its own.

The traces in the following section are used to illustrate the nomenclature and to indicate the clinical significance of certain fetal heart patterns. Although typical traces have been selected, it should be recognised that because of the considerable degree of variation commonly found in clinical practice, a classical trace of any pattern rarely occurs. The classification of FHR patterns that has been adopted is proposed as a guide to the clinician to enable him to decide whether further investigation by pH measure- ment is necessary. Mean pH values for particular patterns are taken from the study by Beard et a! (1971). For reference purposes, a summary of these fetal heart rate patterns and their clinical significance is provided on page 54.

Beard, R. W., Filshie, G. M., Knight, C. A. and Roberts, G. M. (1971). The significance of the changes n the continuous fetal heart rate in the first stage of labour. Journal of Obstetrics & Gynaecologyof the British Commonwealth, 78, 865.

10 FHR PATTERNS

ACIDOSIS (pH725) NORMAL (pH >7.25)

Normal

Accelerations

Baseline bradycardia

Early decelerations

Variable decelerations (uncomplicated)

Tachycardia (uncomplicated)

Late decelerations

Lossofbeat-to- beatvariation

Tachycardia (complicated)

I I I I I I I I I 100 80 60 40 20 0 20 40 60 80 100 PERCENTAGE

Figure 2 Normal

Normal pattern has the following characteristics

a rate within the range of 120 to 160 beats/minute. no change in rate, during the uterine contraction. variability ('beat-to-beat variation') of five or more beats/minute.

A normal pattern is reliable evidence that the fetus is in good condition, and it is unnecessary to investigate the fetus further by pH measurement so long as this pattern persists.

(Mean fetal pH 734±0056)

12 ILLUSTRATIVE FHR TRACES Moan

F1ITiE1I h i'i.iu iii.

iL 11 qrl~ - owl

MEE ME

M ME

MEN

SONICAID Baseline Bradycardia

Baseline bradycardia is a fetal heart rate of less than 120 beats/minute.

The pattern is uncomplicated if it shows good beat-to-beat variation without decelera- tions during contractions as in the upper trace opposite.

This is not an adverse pattern and is probably evidence of a vagal response. It is not necessary to determine the fetal pH unless the trace becomes abnormal in some way. (Mean fetal pH 731 ±0043)

The pattern is complicated if the trace shows any abnormality such as loss of beat-to- beat variation or decelerations. Fortunately this pattern is rare as it is commonly caused by fetal asphyxia.

The pattern in the lower trace opposite is particularly serious showing profound baseline bradycardia with marked loss of beat-to-beat variation. Some recovery has occurred at at the end of the trace but late decelerations are present. The patient should be turned on her side, given oxygen, and the fetal pH determined. If the trace returns to normal labour may continue, but if the trace remains abnormal and the fetus is acidotic, delivery should be performed without further delay.

14

ILL US TRA TI VE MR TRACES

Baseline Brady cardia

Uncomplicated baseline bradycardia — Ultrasound

70 I I73, I- I 4 1- -101 1 IfIIIII SONICAID 0

Complicated baseline bradycardia — ECG 1 - _ {-200 EN 200 200 200

-180 180 100 - 100 11111 _.

I 160 IMIlla l 160 -16.. :._ ' 160 -140 , -140 MI 140 .Aisiihmp,- 140 mmini =1111. 0 iiiiiiiiIIM. -120 120 gm ....1114111 -__ pr y WA 111311 um' aiMF100 -100 100 rk. i 100 r 80 11111111M1111111111.1111. 80 1112 ___!• ,,,...,. _ 8__, 4...„-b RI -60 &NM. 60 Ilia 60 60 MI ME Baseline Tachycardia

Baseline tachycardia is a fetal heart rate of 160 or more beats/minute.

The pattern is uncomplicated i fit is not associated with decelerations during con- tractions. Commonly there is some apparent loss of beat-to-beat variation on the trace which is usually non-asphyxial in origin. This is not an adverse pattern unless it is associated with maternal pyrexia or ketosis. It is wise to estimate the pH and temperature of the mother. The fetal pH should also be measured, but it should be remembered that fetal acidosis is only a terminal event when a fetus dies from intrauterine infection. (Mean fetal pH 733+0052)

Both traces on the opposite page are examples of uncomplicated baseline tachycardia.

The pattern is complicated if decelerations of any variety occur during contractions. Examples of this pattern are covered by the traces of 'complicated variable decelerations' - page 25. The fetal pH should always be estimated when this pattern is present.

16 ILLUSTRATIVE FHR TRACES Baseline Tachycardia

Uncomplicated baseline tachycardia — ECG F t t T1 t 1 -200-- 200 200 1 200 _ -180 180 180 180

, • A .11. A ..obl 14111161ill ihibatir•-••■ . 4 .... • 1 .. Iilil -I IN , 1' 0 or-y • w - 7 T -I 1

-140 -140 140 140 _ -120-' 120 120 120

-100 100 100 100 — - - 80 I BO 80 80

60 60 60 60

SONLCAID

Uncomplicated baseline tachycardia- Ultrasound

200 200 200 -200 in - -180 180 180 - 111 180 .„,..,,, I INK limp, VI.• I IF ...... t 4... - iediriakilir -"i , g ., . - 117. ' 1. i I -140 140 140- 140

-120 ' 120- 120 120 - -100 100 100 1111 100

-80 80 80 80

-60 -60 60 60

SONICAID Acceleration

Acceleration pattern is an increase in fetal heart rate at the start of a uterine contraction, returning to the baseline rate before, or sometimes after, the end of the contraction. It is not an adverse pattern, and indicates good reflex responsiveness of the fetal circulation. No further investigation is required.

(Mean fetal pH 734 ±0033)

18 ILLUSTRATIVE FHR TRACES

Acceleration

Accelerations — ECG

—160-

Accelerations - Ultrasound ____ 1 i Tpi 200 1 200 ME - ------— M -- 130 Er ■ 100 1 180 180 I ii -IL "Id 41 it -I 160 ' 0 .111121511 .- —16... Tafillier , , - _i__ _ "Y711gijk, - a- w .7srirrirr A i "mrogiltilln • i r , di , .1 , f , .. ;Alisabiasi. Skis _4. - 0 140 ----r---- 140

60

19 Early Deceleration (Type I dip)

Early deceleration pattern (Type 1 dip) has the following characteristics

onset of the decelerations is usually at the start of the contraction. recovery of the baseline FH R occurs by the end of the contraction. the amplitude of the deceleration is relatively small usually being less than 40 beats/minute.

A trace that is normal apart from early decelerations is usually associated with a fetus in good condition. However, while such a pattern may be associated with a non- asphyxial condition such as head compression, it may also be an early warning of asphyxia due to umbilical cord compression or placental insufficiency. For this reason early decelerations should be watched carefully - if they remain unaltered no further nvestigation is necessary, but if they develop into 'variable' decelerations it will be necessary to obtain a fetal blood sample in order to estimate the fetal pH. (Mean fetal pH 733±0045)

20

ILLUSTRATIVE FHR TRACES

Early Deceleration (Type I dip)

Early deceleration -ECG 200T-_ 4-4 ?00 - _j_2oo_ 4 - H rHI200 180.L--4 -- 18,-- F- ib30 -4ioo-

-160-- * 160- ------160-

PF I I rc) —120 1,hV 100-t- 100 t4 ___J___10-4 —t-- 1O0- I 80------ -- - 80 -- -- 4------80------ --8O- --

60 t IIL6O ilL. 60

100 100 ------I I ------ -75-- - - --

25 L --H ------25 ---- ---- - ! L

?0

Early deceleration -Ultrasound

200 ._- 2001J_L_J-_ 200-L- -200- -

------1oo - •----- -L------—f------i30 4------130- -- - 160:

120 _4

12 TT4 ° 60 ft:tilF60

SONICAID Variable Deceleration

Variable deceleration pattern has the following characteristics

appearance either at the onset of, or later in the contraction phase. the deceleration has an irregular shape which is variable, with an amplitude of more than 50 beats/minute.

The pattern is uncomplicated f the baseline rate and beat-to-beat variation are within normal limits. Like the 'early' deceleration it may be a preliminary to a more abnormal pattern associ- ated with fetal asphyxia particularly if it appears consistently with each contraction. (Mean fetal pH 731 ±0 048)

22

ILLUSTRATIVE FHR TRACES Variable Deceleration

Uncomplicated variable decelerations — ECG

t 1 77 f 2 00 0 i 00 - ; 1 20 0 ,i, I i 1 r i 1 ti i rr r1 11111 I I00 . r 1'0 .. 1 i ; J 1. 1 1 I L--I --",---- ;-:,- 100 -:; - - 16 0 4----1— 1 1 , I , t • f , t t• II••■ __. Ai:. 't _ td.,.■, ti ,, , • ,.....* I , &Willi ... ..■ ' , , , 1 1 . : , . , , , ., . , , - t --- -- --,t- - _ , , I , 12 0 -1,t 1 I 1 s 1 —I 7 , t ; t_. i : 1 • lOtt - , 100 , t J • -I ; , t 'I I 1I 1.r t , - 130 , , , - - i'.;;;' , -■-• , -1 0 0 ,' r-'rr - --••---33t3 3.- 8 0 ---i--- i { t - • I t - I , :r •_..„ - 1 6 0 ti ' 1 f , j 1. -f

, 10 0 , 1 I t ' • : i , i '

. 1I 1 t t ■ ' " I 1 5 fl-- 4 I 75 '' A- 7- 4-- 75 1 I i i P1111 1- - S • - -, --,t - 5 0 A lI 0 - 5 0 , i ,tI Ii1I I•11,t It

4- i 2 5 AA 7; Ail" fill i11 III 11- _ VIIIIIIIF lii 25 Mil , I 1i I 1It , •t t „.: 0 - t e t ! P I SONiCAID Ci Variable Deceleration

The pattern is complicated i fit is associated with baseline tachycardia and/or loss of beat-to-beat variation. It is an abnormal pattern which may be evidence of fetal asphyxia.

(Mean fetal pH 7 22±0 075)

The clinical significance of variable decelerations is often difficult to determine. Single or intermittent decelerations are obviously of less significance than those appearing with every contraction. In general if variable decelerations recur after turning the patient on her side it is wise to determine the fetal pH.

24

ILLUSTRATIVE FHR TRACES Variable Deceleration

Complicated variable deceleration (with baseline tachycardia) — ECG

1 — J -- I 1 t .-.1 1 11 717 ' II 1 1 ', . , -! 'If ! , 1 : t 1 .. . .11yl , -t '' :iii I . -4 1,,T, - I --,-- ,- tPot , I 1 ,2, i ,. I- . i , 7 , , , . , . , V' ,, . i ,_ ..,_ , 100. , . , ,c,,,, : , ,,,,,,, , . , , ,00 -,,- 1.- . ,0„. t 100 ; -1- . 1 ; I 1,. f,' 8a i I , -f i i , ' . 80 -. . , . + 80 . . ' .- 0'0 .1 7 1 BO ti 4, 80 -. -, , . , , i i i . . . i t '. 60 -. - 60 -.r. ',. 1 4 1 b0 . +' 1- -.-- So 4-- '.-- 60 , --i,- --, -1 60 ■ I . i ! I r I, I,

[ 100 [ i : .' r loo , 7- 100 :- , . T 100 5: rt— T loo i , ! 1- 1 1 ! !, ! i 1 . I I 1 75 ' , . 4. 75 --.- ''- -, 75 • L -1 T5 - ■ 1 1 75 4 I L t- --1- „ L I ■ I , 1 t I 1 , ; ■ '' 1 1 ■ ! ; 1 , 1 , i 1 C 1, j ; , [ -50 1 -, A -,- 1 50' i .i._ ; 1 „ : A 1_ Ai s i , I r I i 1 I , I ' 1 I 't ; I + t -, 25 ,, - ,- 25 4 . 5 _...... ‘,.. i i . 1 t . t 4 ; } I . . , I , 1 , 7 ' !,, 0 , ; 0 I _ 1 i ! ', a ! ! a . t_ , ., i _.: a ,t_ 1.1 .5,,r,,NIC:Ai'Ll V , 2

Complicated variable deceleration (with baseline tachycardia) — Ultrasound , I ,,, I '' 1 I 4 200.} 0' .- 1 .. ,00- , .1, ■ ; ZOO r , -.-- 1 _1, ,,3,::,..: . ,- ., r 203 . .,_ f 200-'. -4- - . . . t ■ t , / 1 , . ', I t I 180 . 1 183 -.-- 4- 18-.) . . . 3,-; . 1 , 4 -f 180 + , . i , i 4 ' f , f . , . ; . f, i , . i '1, , , , J ! 1 0 4'. , -.----160 , f'tf ' • ' °CC, + , . 1 . 160 , , --*- , f f I 1 t )f 1 01 ' + + :-.- 170 - ' + 1- •.', 140 - 1,140 . 4 140 _.' . 1 1 111' - -; ' ' . '. 4, 1 - rr t 7 •I 1 i '1 , i t- -... ' . 1 ____,_ ' kr III t 0 --77 ' • arj, ' . , .0 -1— -' t 1 . 1 '.- ■20 -4-- --14.---, ' 120 , I , . 4, —; - 1 . ' + . 1- 7 ,' i I • 100 I, ; • I, 100 ,, 1 1(1 'l I ;•' ,' . 10 ) - ' , , ,..,0 , - - 100 -f - ---{--- , ; , , ill, 1 1 , • . 4 I • ' t ! 7 • 7 f r an r,-' r . . 1 80 . ' , . 65.. .. 1 ,- 50 -. . 30 , 4- 1 . 1 , ; , -{--, 80 t- 4 ,' . t, ' 60 4, , , . 60 • ,- . 4-- --,- _ . 1 • .., -50 1 ' 60 '4- -; 1 60 . 1- 60 -1--i 1, _ f i t

r 100 ' • 100 . • . l C0 j - . 1 , -t 1 , ,. 1 4 I - ' + I . + . , ; , . t 75 tt , r ' ' 1 i t r .- 15 .--.- 1- 4 7 -", - ■-- 1 I 75 i , 1- -, 75 4 -- --/------i 75 , ■ . r . r 1 .. I tt , r 1 ! .■ ' t t 1 t , 1 4, ',1,a i .0 4-- . ' , . ..j. 1 -.-. 4 t t t .50 4. 1 1 i `' -I- i• t r I t 1 1 1 , ,-I I i i t . . - -1 i i 25 . 25 . 1 5 -, 1 , i-- 25 4---- -+---- ' ..,iv,i ' 25 . • t- 11 1 4 1 , • ; 1 I t 1 i i 1 L ._ , __I__ i ,4 L' 0 i - +- -.1_ 1 6 .' _ t ...... 0 1 _1 ' 1 ._ .i__ 0 .,_ soN■cAtO Complicated variable deceleration (with baseline tachycardia and loss of beat-to-beat variation) — Ultrasound

; 1 1 T ■ '+- I 1 i i i 1 ;400 .t. i '7 1 I 200 -,,--- 1 4- --i- L 2, 00 , .. ?oc.., L 1. a oo ,,. i-- 41 1- 'r . zool— 1— ■ , 4 41 ' . I ' ' i I . ■ 80 180 .--1,, , ,,, ra.) r e: --1 --; + re0 . r r r! 0 1 I- -180,— — L, ' .... r60 r r — 60 011101k 1. - 1'. 1 it r 1 . I. . , ■ r i r 1 i ; 140 4 ■,- , 4 140 t : -,, 140 . i- t r, 142 ■ -- 0- -. , i. .kr 140-4 --t- r I 1 ; ■r• . V , ; _ ; . ; .. . 1. '• , .-- -!--12‘..; ---2.- ; ., 4.• 1,-,0 . If 1._ ;.: ;•"0 ' '. .. 4 , 44,_ 1 ; ; ,I. ; • , • ; f ; t . '

I ' i 1 4- 60 - ..' -,I. ! 4- • 60 . -, - ,..,0 ' . -, • ; 4- 60 -1- - 1-1 I

COO j. 1 100 . 101 : I -V' , , , 4 : t ' , 5 -, , 1, _ -75 --- 1 , i i i ■ r r I 1--5. 0 I 50 5 5 -50 - 7 1 . t-I ' . ' , - 1 1 1; 1 250 25; -- I 1 ; I t 1 - - . L . I _ 1t SONICAtu 6 . .!.1 Late Deceleration (Type 2 dip)

Late deceleration pattern (Type 2 dip) describes any deceleration whose lowest point is past the peak of the contraction and thus has lag-time. For example, a variable deceleration with lag-time is described as a 'late variable deceleration'. In general the greater the lag-time, the more serious is the condition of the fetus. The most ominous form of late deceleration in this respect is the one that is shallow with an associated baseline tachycardia and loss of beat-to-beat variation as shown in the upper trace opposite. This pattern was recorded in the recovery phase following the administration of epidural anaesthesia. (See Case History 3 - page 42 - for a discussion of the effects of this drug.) (Mean fetal pH 724+0 073)

Another variety is shown in the lower trace opposite. (Note that the trace was recorded by ultrasound so that it is unwise to rely entirely on the apparently good beat-to-beat variation.)

26

ILLUSTRATIVE FHR TRACES Late Deceleration (Type 2 dip)

Late decelerations — ECG , 1 ;, I i---- - ft- 200-4- ----1---]-- 200---i -200------1----- i I , — - 180- - 4 1:20 • - 180 I 4- 4 4-130- i 4 I . ....„ 41 Go . i ___ _ 1 160 . _ . 1 i ---- osnito . i ---, I--140 ; 140 I , 4 1 ; 1-120 _ # 120 41 -120 -111 1 i 1 . 4 i 1 1 100 [-- , -t- _ . -1- I I I, ' I I

1 i 1 1 1 1 60 GO 1- --,- . T GO - - i 1 -It-60 1--- —7 1 1

- i 100 F00 7 100 1001 I 1--- I 1 I ; I I i_ I :,...... "\\1\175 --, --r- -1 7 75 I , T75 I ! I ' I 50 k • 0 • i If i 1 r- 25 I- - -; 25 -,, - 25 4-• 25 1 1 I I [_ :0 _1. 1L LJ L .0 _I_ 1 I _ .‘ 0_1 0 SONICA-ID 0

Late decelerations — Ultrasound

- o v - T T 100 T- 100 7 ■ 1007 i 1 1 I . r Ai _ i 4i 75 75 - m _ - 1 -50 rkr 50_ owErik _ b 25 aid -25_ II 25 25- ______- R _... Loss of beat-to-beat variation

Loss of beat-to-beat variation describes the instantaneous fetal heart rate with a variability of less than 5 beats/minute. At the moment, until more precise methods of quantitation are evolved, it is necessary to assess beat-to-beat variation from the appearance of the trace.

The pattern is uncomplicated i fit is not accompanied by decelerations.

The cause of uncomplicated loss of beat-to-beat variation is not fully understood but it is known that a number of drugs commonly used in labour such as pethidine and diazepam reduce FHR variability. Thus a 'normal' trace may appear abnormal because of the absence of beat-to-beat variation even though the fetus is well oxygenated.

(Mean fetal pH 7 30+0 061)

The pattern is complicated if the loss of beat-to-beat variation is accompanied by an abnormal baseline or by decelerations.

A pattern of this kind is frequently associated with asphyxia to some degree particularly if the deceleration is late and shallow. (See the patterns of complicated variable decelerations-page 25, and late decelerations-page 27.)

(Mean fetal pH 7 24±0 073)

n general it is wise to estimate the fetal pH if the trace shows a persistent loss of beat- to-beat variation.

Uncomplicated loss of beat-to-beat variation is shown in the recordings opposite. The ultrasound trace shows an abrupt change as beat-to-beat variation disappears following drug administration.

28 L US TRA TI VE FHR TRA CES Loss of beat-to-beat variation

Non-asphyxial loss of beat-to- beat variation - ECG - ,-200----- 200 -: - +

Uncomplicated loss of beat-to-beat variation - Ultrasound

200t 200 2O0- -

---1d0 ---..----.-- ------ ------130- Z10_ ------—160

14 0

-120------i --4—i------120 ------120- - * -

- C)- - -r- 60 -

S0NCAID @ Normal

Normal contractions n the first stage have the following characteristics • a frequency in the range 3 to 4 contractions every 10 minutes • a duration up to 75 seconds • basal tone of 5 to 12mm Hg • peak pressure in the range 30 to 60mm Hg

Upper trace First stage contractions recorded by intrauterine catheter Frequency 35 contractions every 10 minutes Duration 70 seconds Basal tone 5 to 7mm Hg Peak pressure 45 to 65mm Hg

Middle trace First stage recorded by external transducer Frequency 3 contractions every 10 minutes Duration 65 seconds Basal tone and peak pressure cannot be recorded by external means. N.B. Paper speed 3cm/mm.

Lower trace Second stage recorded by external transducer M ulti-spike contractions typical of second stage due to superimposition of maternal 'pushing' and respiratory effort. Frequency 45 contractions every 10 minutes Duration 60 to 85 seconds.

30 UTERINE CONTRACTIONS Norm W

Normal contraction trace - internal ...... _ r 100 I - 1-- i 1 -100 i i i T t 1007— 100 _ 1 I , . 1 I i 1-- 75 -1-- +1 - -1 — 1 i I 75 f —75

Normal contraction trace- external (at 3 cm/min )

— 100 1 I-100 I t r00\ 100 ftt-r 1 75 7 —75 I I 75 t

Normal second stage contraction trace - external

SONICAID Abnormal

Respiratory artefact is exhibited on the upper contraction trace opposite which shows first stage uterine contractions with irregular wave form caused by maternal respiratory effort. Patient restless and hyperventilating.

Abnormal uterine contractions of three different types are shown together opposite.

Upper trace Severely disordered uterine activity with basal tone raised ntermittently from 0 to 25mm Hg. Occasional regular contractions followed by 'notched' contractions with from 40 to 75mm Hg.

Middle trace More normal trace of uterine activity. Irregular contractions with peak pressures ranging from 25 to 65mm Hg. Note how a contraction which appears normal at the onset may be followed, before full uterine relaxation has been reached, by another contraction (often referred to as 'coupling').

Lower trace Major abnormality is shown by a tendency for the basal tone to remain elevated and an abnormal frequency of 6 contractions every 10 minutes.

These three cases are examples of the over-administration of oxytocin and were induced without rupture of the membranes. Similar records are occasionally obtained in women n spontaneous labour usually with cephalopelvic disproportion.

Management Reduce the amount of oxytocin infused until a normal pressure trace is obtained.

32 UTERINE CONTRACTIONS Abnomnzi

Respiration artefact

25-

SONIC MO

Abnormal contractions (over- administration of oxytocin)

100 1 00 - r

7 - + t -

ILI I1I 'N L

----

0 75- .-75 -

-- 25--- -- --a-- - L:-: Poor application of scalp electrodes This type of trace with a 'flat' appearance accompanied by multiple artefacts is evidence of poor application of the scalp electrode. Care must be taken during application to avoid contamination of the electrode with antiseptic cream. Application is done best under direct vision through an amnioscope so that the fetal skin can be thoroughly dried. If a clip electrode is used the points must be checked to ensure that they are not contaminated with insulating material and that the angle of the points is correct.

Poor placement of ultrasound transducer Upper trace Trace showing many artefacts diagnostic of failure to place the transducer on to the optimal site on the mother's abdomen for recording the FHR.

Middle trace (transducer repositioned) Better trace than previous one, but some artefacts still present.

Lower trace (transducer repositioned again) Good ultrasound trace without artefacts.

34

RECORDING ARTEFACTS

Poor electrode application SONICA 10 0 - i , o - i 4 i - r- - 0 1 4■ t - +■,1 -160 0' i8.'... ' -I , --..i 0 1 --‘, 218 00

', -_, ..„ . . 140 00 iqr ,.....- - •• •••.-- --,- ... riii0o -1, _ .' ...I.,. ■ _ , .. 1_ t 1 j -i , , ..q.i."7 ti, ,1 _ ri ,z i lkv 1 0 , , 4... , . 1 _ „ ■ 1 . '" ' • '1.. - 40 - 4.c - 1 - a ■ 1 I I- i_ -I , - 1 ' 3 r-- -, ---4-- 120 -,-- 1 1 120 i 1 120 • i 11 ,, 1 1 T , , • ,^ . .., i- jr-loo 2-- 100 r- ',-- ---+ 100-i J.. , 1 t ! 1 f 4 I4 I 4e -', o 4 I 80 L --4-1 4 t ■ t 1 4 , ■ 44- ' • t - 4- • 1 ', 60 --i -1 --L-1 60 --!-- 1 -1- ..' ' 1 - 1 I 1 1 1 I 1 l 1,

Poor placement of ultrasound transducer . . SONI 0/1 ID 0 . . : ---- f -- - --, - - - - . , .,••2.-,t, . 1 i • t r-- 00 -4 - — 1---, . t" 2001,, t -1ft,i — • ..' ••,c, ' I - - ' • ,.• 400 1 -1',- -..30 i 1 180 • f _. . Ii trit, c• .' , - , • 1 ...am._ JA. iit ' . r# 1.° ._,___-__,__- 160 6° ^i 111-'- 74-14r - t• [ - f , _ ._ .. •1 l irr I , A iiiiviiiimIII I .. rji ii-i.A 41 .... _ , 1 ti , f- 14,,,, -4 • ,40 .1- •-• . -, -1.1, . 1II iihrt- 1 2 . 0 1- r i II -Ai 14D rtfi- : .4. . . .. 20 -4- -4-----1-120-1---- . . - -- 1 i. 1. --t-r i 1-- - - - 1-. 00 jr- -'- 10 .' -«---- • ------4- 100 -4-- . 111. I- i f - -80 -4-- -.I-- e t t 86 . . 1 , ri ■ .1 1 F-- - 60 --, -4-1 I 60 1 --1

, SONICAID. 0 , , 1--' 1 1- 1 f 1 I- , 200 -1--- -1- I 210 _L -t ' --200---r- t 1 T 1 — , i , r t 1 ,., -- ---; It' ' 4- - '80' I -I, 1, i 1, ___,. , r t ---t 1 f -, , --,, ,...-., ----I- IGO *---- _____A. I ,60 f- -160 , ■ 1 ■ . '. ,, ' I ' 1 1 1 . I iii , I; 1111K11 diViL , 1 '1. 1' 1 ■ ' .4. All 1 1. 'ili 1 _ I ' ' _ , , . ,, 1 .,■ g i .„ , 11 1 10406E vo I r 4 12 0 1 1 ., , , t 1 1 4 -..- 1 . 4 -14-100 -It- :- * I .--4: 100 -4 1 -,1'F- - i -1,,- _ ,i 100 -1:' : • ■1--1----- e , i I . 1 I I 1 . S. 8 .5 4 - 80 --,, - ---s- i,_ 83 , ."- ,- ----i-- -t 80 1-- 4„. _ , 4 , , , I t ._ -0 --- f CO _l__ 604 ■ -:- t j —1 t

, SONICAID 0 . . ■ r + r I- 1 200 -, .,_i 1 200 i 200 I , 1 !-- --41- . . ; . . ,. c _ - rleo I ■ ' , 1 90 -8044- 1 , I 16S I --,-- ! .0 1 AV 1, 1 LI . 71W-. ' , NIIIIIITYI __ .11 P 1 1 II 0 , 4 4 . A 1 ail glitillakift'll.11.!..1114 1 , . ., ./ al 140 1lir I r , - • ' ' .' 4 1 1 i I --`, - ..-111- -1,, ' .2. ' L. 2C -' 'fr .14 InaaLINI1120 L 120 L-12. , 4 4 4 4 i I k -,- - - L 100 ._,_ 4 -44 1, 100-1- t 100 1 ,.• i . I 1 i I -I, 1 .. . , . 1 t 1 -,4 1. SC 80 1- .__ + r i i 80 1- 1 i f ,-- 80 I . . , - -,I , ,_ 4,- •01 - -,,--- 60 ' - 60 1 - i 60 - i' I 1 4 60 i . ' ', ' . L I I I I I 1_ i Poor placement of ultrasound and external pressure transducers which are subsequently correctly repositioned Multiple and prolonged ultrasound artefacts accompanied by a poor pressure record. Repositioning of both transducers resulted in a satisfactory FH R and pressure trace.

Halving artefact FHR 190 beats/minute. Genuine recording given intermittently interspersed with false recording at approximately half the rate. This artefact is rare and is easily recognisable. t can be overcome by changing the signal, e.g. from ultrasound to ECG.

36

RECORDING ARTEFACTS

Poor placement of both external transducers . . -200 200 200 _ , - -± -130 130 __r130 130 ri--- Ilia _ --160 F .Tipnritl 160 1 k - ition ----130 ---.--al — Mo. 111"1, la l -140 1 1 i', 'T I V v. ,„ - • . , 120 1_ .-• 1-7- 1111141 120 - r L,_ _r. r -- i-----r- r r 11111 1-100 100 ---1---[.r 100-1- 100 ill , r 1 t -1- 60 60 lin 60 r 1 1 .

SONICAID ©

Halving artefact

-200 Nwillevi 200 200 4./-"Swe 6. 2090...szt- .G.A111011111,11F -180 , kali 180 M. . 130 130 -160 11111111 160 — 160 160

1 .. . --.------140 m -140 -140 140 ___ __ 1 -- -- -120 111111111. mi 120 120It 120 - -100 100 10 - -80 80 80 80

-60 60 60 60 _

SONICAID 0

37 Normal

Changes in FHR and uterine pressure patterns which occur at full dilatation FH R-ultrasound Contractions-external transducer

Upper trace End of first stage - uncomplicated variable decelerations with contractions 4 every 10 minutes. Management Careful observation only.

Lower trace Second stage - uncomplicated variable deceleration with a more disordered pattern. Good beat-to-beat variation and normal baseline remains. Contractions 5 5 every 10 minutes and typical of second stage with superimposed multi-spike artefact due to pushing by mother. Management Observation, noting if decelerations become prolonged or 'complicated' which is indicative of possible fetal asphyxia. Measurement of fetal pH even at this late stage may be useful in deciding on management.

38 CASE HISTORIES Normal

60

SONICAID

--, -- _ 200.-4- 200 200 _____ 200200 - -100--1- 180 100 - l 130 in

loi■ii -160 16 t 1I 1' 0 60 i t . _ _ 40 aiii„ , IIIIIIran A I ., littellilr ,REarm mruk Nair iffilinli Lill Egg IT !LIMNS' -120 II. 111 120 111111111110 120 'MVP Mr Ark 120 ismilVaillial MIMI AMU 100 0 illa III V:, X 10. 111 11 100 ME till 80 I I- 60 I GO MIN 60 I 60

SONICAID 0

39 Effects of drugs

2 Recovery following episode of acute asphyxia (post-epidural anaesthesia) FH R - scalp electrode Contractions - external transducer

The three traces opposite form a continuous record showing the recovery following an episode of acute asphyxia. Upper trace Late decelerations with loss of beat-to-beat variation and baseline tachycardia. Contractions 45 every 10 minutes. Middle trace Decelerations have disappeared with return to normal baseline. Contractions unaltered. Lower trace Normal beat-to-beat variation with normal baseline. Occasional ate decelerations. Management Careful observation. Fetal pH determination if late decelerations persist.

CASE HISTORIES Effects of drugs

f - 180 H r 182) 182) 180 t 30 ISO

141)

12.0- Izo

00 100- 100 i 80 - 80 - 8 r 80 4 60 604 60 60 604 60T +4

200 H H 4L00 4 200 f_ 20C - 420O4__ 200-- 18C) T 180 ::

1204— --

1ooH i oo ; L0 :rfioo - 80 60 —t 80 i 60 4 T 60 60 60

SONICAID ©

200 . i. L2L —L 2001 1001IIi_f__4_ 1 2001 - 1804 J 100 180 L

FIN I- F120 20- 100 loo -4 - 10Y 4 o100 J

) 804--- 80 ) 80r 80 80

60 601-L4 60 r 60 T T 60

41 Effects of drugs

3 FHR changes following epidural 'top-up'

FHR -scalp electrode Contractions-external transducer

Episode of bradycardia unrelated to contractions starting 4 to 5 minutes after epidural top-up'. Bradycardia maximal 11 minutes after 'top-up' and lasting 4 5 minutes followed by recovery as FHR returns to normal baseline 2 5 minutes after patient turned on her side. Then single late deceleration followed by baseline tachycardia. Contractions characteristic of second stage.

N.B. The two traces forma continuous record.

Management Epidural 'top-up' should have been given with patient on her side. n this case patient was on her back but was turned on her side as soon as bradycardia was recognised while, at the same time the syntocinon infusion was turned off. Immediately an improvement in the FH R trace was apparent.

Epidura/Anaesthesia is commonly used in modern obstetric practice for pain relief in abour, and acts by anaesthetising sensory nerves supplying the uterus. It also affects the autonomic nerve supply with a result that there is a tendency for maternal hypotension to develop which is most marked in the utero-placental circulation. In addition, local anaesthetic agents are known to be rapidly absorbed from the extradural space into the maternal circulation and then to cross the placenta into the fetal circulation. Ab- normalities in the fetal heart rate ranging from a short episode of tachycardia to profound and prolonged deceleration are frequently seen following the administration of epidural, caudal or paracervical anaesthesia. It is often difficult to determine whether these abnormalities in FHR are asphyxial in origin or due to the 'quinidine like' effect of local anaesthetic agents on the fetal myocardium. However these changes in FHR are an indication of the potentially harmful effects of regional anaesthesia (excessive dosage or too rapid administration, or the patient in the wrong position) and of the need to monitor the fetus when epidural anaesthesia is used.

42 CASE HISTORIES Effects of-drugs.',

-200 -200 200 200 -180 180 180 100 ___ - - Ali I aid 160 il"A"" 160 160 v. Ili !VIA 1 . I i MEMrirliLIPTI IT ' Vf:16■111r -140 140 . UMW M.. ■ 1 npe 140 11 tavilAtwar r :i- r -120 NI 120 Li 120 I IVAIMMiglE1111 120- 100 100 100 IIIIIIIIMIallIP• loo 80 III END RAL OPPEDA9P M 80 Isal 60 60 60 60

SONICAID O

-200 1 200 --. 200 200

-180 180 71:i im IF - - -160 - anciii.lur..,,..,.,..y.i., IA 160 160 -140 iimmillaininial 140 i ...... m. 140 140- 4111111111Iii. -120 11111111111.Prill 120 LITIIIIIIII 120 120 - f11 avuorin -10. WiiiliL111141 m__o 11111111111win= loo WO- 11211=11 -80 80 80 80 _ -60 60 60 60 - _

SONICAID

43 Effects of drugs

4 Effects of drugs administered during labour on the FHR pattern FH R - ultrasound Contractions -external transducer

The trace shows the effect of drugs such as valium and pethidine on the beat-to-beat variations. Prior to administration of the drug there is a normal heart rate with good beat-to-beat variation. Within two minutes of drug administration there is a recognis- able loss of beat-to-beat variation which persists for 9 minutes. There is then a sudden return to normal FH R which occurs spontaneously. N.B. The two traces forma continuous record. Management Observe the patient. A fetal pH determination is only necessary if the loss of beat-to-beat variation becomes complicated by a baseline abnormality or decelerations.

44 CASE HISTORIES Effects of drugs

200- -. - •- --200 I

-160 160

11 10,

- ioo------ - -o H 4 -- -- :4L INVALIUM

SONCAD 0

20O---t- I - ---- 2OO - I - T11- F 140

120- iii:::r"iiiii

- i ON 100 -- -, - i

- f 60 f o-- -- Uterine hyperstimulation

5 FHR abnormalities accompanying uterine hyperstimulation FHR-ultrasound Contractions-external transducer

Upper trace Early decelerations with normal baseline. Contractions 3 every 10 minutes stimulated by 8 milliunits of oxytocin/minute. Lower trace Variable decelerations with baseline tachycardia, some of which have lag time. Contractions now 4 every 10 minutes following ncrease in oxytocin infusion to 10 milliunits/minute. Management Turn off oxytocin infusion and turn patient on side. If FH R trace becomes normal oxytocin can be increased again slowly to previous concentration that preceded appearance of FH R abnormalities. f FHR abnormalities persist collect fetal blood sample for pH determination.

46 CASE HISTORIES Uterine hyperstim ulation

- 200- 2004------200 1

-140 --120 __ iI4' :i t - -

80r- -60- -- -60-4 - - 60

SONCAU) ©

I, ______0• == •1 ______

Lh

i I

• 11 • __ - &• Ii •- I

47 Uterine hyperstimulation

5 FHR abnormalities accompanying uterine hyperstimulation (continued) FH R - ultrasound Contractions - external transducer

Upper trace Disordered FH R pattern to variable deceleration and baseline tachycardia. Contractions - very abnormal with multiple peaks and raised baseline. Management Turn off oxytocin infusion (16 milliunits/minute) and turn patient on side. If FH R trace becomes normal oxytocin can be increased again slowly to previous concentration that preceded appearance of FHR abnormalities. If FHR abnormalities persist collect fetal blood sample for pH determination.

FH R - scalp electrode Contractions-external transducer

decelerations of small amplitude. The favourable features are a normal baseline with only mild loss of beat-to-beat variation. Management Reduce rate of oxytocin infusion until frequency of contractions is no more than 4 every 10 minutes and turn patient on her side. If late decelerations persist collect fetal blood sample to determine fetal pH.

48 CA SE IllS TOR IES Uterine hyperstimulation r

5• ______0• S. 3 • ,J . a..____________

.: rat' u!

SIMMONS

U __ — — — 1!1!i 1'. 1111 1. I '11

SONICAID - LE

:':

:: ii J i1T :

SONICAID

49 Miscellaneous

6 Uterine hyperstimulation due to blockage of oxytocin infusion catheter

FH R - ultrasound Contractions - external transducer

Oxytocin being administered by infusion pump when, unnoticed by staff, the in- travenous catheter became blocked. The catheter was cleared and the oxytocin infusion started at the concentration immediately prior to blockage. Contractions previously regular showed an immediate increase in basal tone lasting for 4 5 minutes. The episode of hyperstimulation was accompanied by FHR bradycardia to 80 beats per minute with full recovery only when the uterine tone had returned to normal. Management f infusion stops, clear intravenous catheter, flush through drip tubing and start oxytocin at lower concentration with careful observation of FH R and contraction trace.

7 Uncomplicated loss of beat- to-beat variation associated with maternal pyrexia

FH R -scalp electrode Contractions-intrauterine catheter

Loss of beat-to-beat variation and baseline tachycardia although no decelerations present. Temperature of mother 38°C. Fetal pH 7 30. Management Progress of labour in this case was rapid, the patient delivering within 4 hours of the appearance of pyrexia. Abnormalities in continuous FH R record and fetal pH only precede intrauterine death by a short while and cannot be relied upon as an index of the condition of the fetus.

50 CASE HISTORIES Miscellaneous: Miscellaneous

8 Effect of posture on FHR

FHR-scalp electrode Contractions-external transducer

Patient known to have a tendency to develop supine hypotension. Three minutes after turning patient on to her back her blood pressure had fallen from 140/70 to 80/unrecordable. FHR fell from 140 to 100 but recovered as soon as patient turned on side. Effect reproduced a second time.

Management All patients should be nursed on their side during labour. If they are not, bradycardia (or any FH R pattern suggestive of fetal asphyxia) should be an indication for turning patient on her side and giving her oxygen by face mask.

9 'Bedpan effect'

FH R - ultrasound Contractions-external transducer

Deep and prolonged FHR deceleration accompanying prolonged uterine contraction starting as patient is put on to a bedpan and only returning to normal when she comes off.

Management Avoid use of bedpans in labour. The marked rise in intrauterine pressure may be harmless to a healthy fetus but can result in marked deterioration of the condition of a fetus that is already compromised.

52

CASE HISTORIES miscellaneous

------ ------100— ioo- --- '—U- - -100-

0 8O L 4 SJDE BACK L " T------44~? - ~ -

• • ______I S • S rii:

• __1_ ILIMME__ S __

. 'uIu:_Ji_!II-Mw VAL% inks

IThIzI-iIi SONICAID

53 Summary of FHR patterns and their clinical significance

PATTERN CHARACTERISTICS CLINICAL SIGNIFICANCE

Normal Rate within the range 120 to 160 beats/min. No rate change during contractions. Beat-to-beat variability > 5 beats/min Not adverse

Good beat-to-beat uncomplicated variability Not adverse Baseline Bradycardia Rate <1 20 beats/min

complicated Any other abnormality Adverse

Not adverse but should uncomplicated No decelerations be observed Baseline Tachycardia Rate >160 beats/min Decelerations of any complicated variety Adverse

Acceleration Increase followed by a decrease in rate during a contraction Not adverse

Onset at the start of the contraction. Recovery by the end of the contraction Early Deceleration Not adverse but should Amplitude <40 beats/mm n be observed

Irregular shaped Baseline rate and beat-to- Not adverse but should uncompcaedli t deceleration beat variability normal be observed Variable Deceleration Amplitude >50 beats/ Baseline tachycardia and/ complicated Adverse min or loss of variability

Late Deceleration Any deceleration where lowest point is past the peak of the contraction Adverse

No declerations Not adverse but should uncomplicated normal baseline be observed Loss of beat-to-beat Variation Variability <5 beats/min Decelerations and/or complicated Adverse abnormal baseline

When the pattern is 'adverse the fetal pH should be determined. 1 r- 44, 1 1 Llle pattern is not adverse but should be observed' the fetal pH should be determined if the trace develops any other abnormal features.