ASSESSING CERVICAL LENGTH
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Transcript ASSESSING CERVICAL LENGTH
Cervical Insufficiency
(Cervical Incompetence)
aka “too easy out”
Brian McCulloch MD
Maternal – Fetal Medicine
March 5, 2011
FIRST
RECOGNIZED IN 1658 BY COLE
AND CULPEPPER
THE MANAGEMENT HAS BEEN MORE SO
SURGICAL THAN MEDICAL
ABRAHAM LASH AND HIS BROTHER
WORKING HERE IN CHICAGO
REMOVED A PIECE OF TISSUE FROM
THE Cx ISTHMUS AREA IN THE NON
PREGNANT STATE (THIS LEFT ~ 45 %
INFERTILITY )
V.N.
SHIRODKAR FROM BOMBAY
INDIA IN 1955 ADVOCATED
ENCIRLING THE INCOMPETENT
CERVIX WITH FASCIA LATA. HE
PLACED THE SUTURE MEDIAL TO
THE BLOOD VESSELS
IAN
MCDONALD FROM MELBOURNE
AUSTRLIA IN 1957 COMPILED 70
CASES
MOSTLY BETWEEN 20 – 24 WEEKS
NO SUCCESS LESS THAN 20 WEEKS
NO TOCOLYSIS
EVEN TRIED TO TIE AMNION
PERFORATIONS
EMBRYLOGICALLY
IT IS DERIVED FROM
THE FUSION OF THE MULLERIAN
DUCTS AND SUBSEQUENT CENTRAL
ATROPHY
THE CERVIX IS PRIMARILY FIBROUS
TISSUE WITH SOME MUSCLE
THE PROXIMAL CERVIX MAY HAVE UP
TO 29 % MUSCLE AND THE DISTAL
PORTION LESS THAN 10 %
DURING
PREGNANCY THE
MUSCULAR UTERINE ISTHMUS
DISTENDS AND ELONGATES
BETWEEN 12 TO 20 WEEKS
BEFORE 15 WEEKS CERVICAL
MEASUREMENTS ARE DIFFICULT ON
ULTRASOUND AND NOT
RECOMMENDED
NON PREGNANT CERVICAL TEST
ARE INACCURATE OR UNPROVEN
AND NOT RECOMMENDED TO Dx
INSUFFICENCY
HEGAR DILATOR SIZE 8
TRACTION TEST USING AN
INFLATED FOLEY CATHETER
INTERNAL OS MEASUREMENT
>8mm ON HYSTEROSALPINGOGRAM
If a Non – Pregnant HSG or a
Sonohysterogram or a MRI does
diagnose a septum or anatomic
abnormality then it can help alert the
clinician to the possibility of a
cervical issue or a factor leading to
preterm delivery .
ONE
PER 222 DELIVERIES TO ONE PER
182 DELIVERIES ACOG PRACTICE BULLETIN 2004
OTHER AUTHORS HAVE A WIDER
RANGE OF 1 IN A THOUSAND TO 1 IN A
HUNDRED
LUTHERAN GENERAL HOSPITAL
CERCLAGE STATISTICS
1989 78
1990 62
1991 48
Gradual
painless dilatation and
effacement of the cervix with bulging
and later rupture of the membranes
Typically short labor
Progressively shorter labors with
subsequent deliveries
Progressively earlier deliveries
Vaginal
or lower abdominal pressure
Frequent urination
Increased vaginal discharge (watery)
Bloody or mucus discharge
Congenital
Mullerian anomalies with
the highest risk with bicornuate and
unicornuate utrei
Abnormal uterine shape
Also abnormal cervical muscular
content( Ehlers – Danlos syndrome )
Acquired incompetence
Traumatic
cervical procedures (cone
bx)
Cone bx’s with a height of > 2 cms is
a risk factor
Obstetrical cervical lacerations
Iatrogenic
Embryological Drug induced (DES)
(about 25 % have structural defects)
THE
INCIDENCE OF PRETERM BIRTH
IN THE USA HAS BEEN INCREASING
FROM 9.4 % IN 1981 TO 12.7 % in
2007 Martin Nat. Vital Stat. Rep 2009;57:1
- 102
RELIANCE ON RISK FACTORS ALONE
WILL FAIL TO IDENTIFY MORE THAN
50 % OF PREGNANCIES THAT
DELIVER< 37 WEEKS CREASY AJOG
1980 MERCER AJOG 1996
DIGITAL
EXAMINATION
SPECULUM EXAM
TRANSABDOMINAL ULTRASOUND
TRANSPERINEAL OR TRANSLABIAL
ULTRASOUND
TRANSVAGINAL ULTRASOUND
Ultrasound assessment of the
cervix
Vincenzo Berghella MD 2003
Trans
abdominal scanning needs a full
maternal bladder and can therefore
elongate the cx length
can be very difficult to see the
external os
Transperineal cervical
measurements
Gas
of the rectum will hamper
visualization of the cx especially the
external os
Transvaginal technique
Enlarge
the image so that it occupies
about two thirds of the total image
Obtain 3 images and record the
shortest.
Transfundal pressure should be for
about 15 seconds
Generally sonographers should be
supervised for about 50 procedures.
Check the Equipment
–
–
Appropriately cleaned w/ soap & water +
soaked
Use 5 to 7 MHz endovaginal probe
–
Make sure the image is set to “EV”
Don’t use 8 MHz – poor tissue penetration
(endovaginal )
Not Obstetrical or Abdominal
Empty Maternal Bladder
–
–
Void just before the exam
If bladder is seen to be large, stop exam & void
again
CONSISTENTLY
UNDERESTIMATES
THE CERVICAL LENGTH COMPARED
TO VAGINAL PROBE ULTRASOUND
HIGHLY SUBJECTIVE
NON- STANDARDIZED
SERIAL
DIGITAL EXAMS IN THE MID TO
LATE SECOND TRIMESTER IS USEFUL
IF THE EXAM REMAINS NORMAL
UNFORTUNATELY ABNORMAL CERVICAL
FINDINGS ARE ASSOCIATED WITH
ONLY 12 - 20 % OF HIGH RISK
PRETERM DELIVERES AND EVEN LESS
IN THE LOW RISK PATIENTS ~ 4 %
THERE
IS A STRONG REPRODUCIBLE
INVERSE CORRELATION BETWEEN
CX LENGTH AND PRETERM DELIVERY
IF THE CX LENGTH IS LESS THAN
10 % (25 mm) THERE IS A 6 FOLD
INCREASED RISK OF DELIVERY
PRIOR TO 35 WEEKS
IAMS NEJM 1996;334:567-57
PROGRESSIVE
CX SHORTENING TO
20 mm OR LESS
FUNNEL LENGTH >16 mm OR
FUNNELING >40 %
MEASUREMENTS MUST BE
OBTAINED TRANSVAGINALLY
WHY
IS LENGTH RELATED TO
PRETERM DELIVERY ?
OCCULT CONTRATIONS
BIOLOGIC VARIATION
LOWER TRACT INFECTION
UPPER TRACT INFECTION
CX
LENGTH OF LESS THAN 15 mm
AT 23 WEEKS OCCURS IN LESS
THAN 2 % OF LOW RISK WOMEN
WHEN THIS DOES OCCUR IT IS
PREDICTIVE OF PTD
< 28 WEEKS IN 60 % OF CASES
< 32 WEEKS IN 90 % OF CASES
Where to Put the Calipers?
Where the
anterior and
posterior walls of
the canal touch
Spend enough
time to see
whether a small
echolucent area is
stable or is going
to open up
YES
NO
BERGHELLA’S
STUDY IN JAMA IN
2001 SHOWED A SENSITIVITY OF
69%
BUT IF ONLY THE INITIAL
MEASUREMENT WAS USED (16-18
wks) THEN THE SENSITIVITY WENT
DOWN TO 19%
VIABLE
DELIVERY RATE OF 70 – 90
%
A LOWER RATE OF DELIVEY PRIOR
TO 33 WEEKS (13 % COMPARED TO
CONTROL OF 17 %)
General a higher rate of tocolysis
usage 34% vs 27 %
Higher puerperal infections 6% vs 3
%
CERLAGE
GROUP HAD LESS
DELIVERIES BEFORE 37 WEEKS BUT
NO DIFFERENCE LESS THAN 35
WEEKS
CERCLAGE HELPED IF CX LENGTH WAS
<25mm’s BUT IT DID NOT CHANGE
THE OUTCOME IF VERY SHORT CX
<15mm’s
TWINS HAD A INCREASED DELIVERY
LESS THAN 35 WEEKS AND A HIGHER
PERINATAL MORTALITY
NUMEROUS
STUDIES HAVE
CONFIRMED THE ASSOCIATION OF
CERVICAL SHORTENING AND PTB
REVIEW OF 35 STUDIES HAD
SHOWN SENSITIVITY FROM
68
– 100 %
SPECIFICITIES FROM
44 – 79 %
PROSPECTIVE
STUDY OF 2900 WOMEN
AT 24 AND AGAIN 28 WEEKS (LEVEL II-B
STUDY )
40mm
35mm
30mm
26mm
22mm
13mm
RR=2.8 PTD
RR =3.52
RR =5.39
RR= 9.57
RR=13.88
RR=24.94
VAGINAL
PROBE MEASUREMENTS
CAN SUPPORT A DIAGNOSIS OF
CERVICAL INCOMPETENCE BUT
SHOULD NOT BE THE SOLE
CRITERIA
RESIDUAL CERVICAL LENGTH IS
MORE IMPORTANT THAN THE OTHER
MEASUREMENTS
RR OF PTD AS CX LENGTH
SHORTENED
25
20
15
RR
10
5
0
40
35
30
26
22
13
ROUTINE
USE OF CX LENGTH IS NOT
RECOMMENDED BECAUSE IT LACKS
ENOUGH DISCRIMINATORY POWER
INTRINSIC
WEAK CERVICOISTHMIC
JUNCTION
SOME STUDIES HAVE FOUND THIS
TO BE AN INDEPENDENT RISK
FACTOR FOR PTB ( INDEPENDENT OF
CX LENGTH )
CERVICAL STRESS TEST
Transvaginal Cervical Sonography
Illustration by James Cooper MD
Found in Callen, 4th edition
20
years ago Zilianti described the
continuum from a “T “ to a “ Y” to a
“V “ and finally to a “U” shaped lower
segment.
Moderate funneling defined as
25- 50% cervical shortening had a
increased preterm birth of 50 %
Cervical Effacement = T Y V U
T
Y
V
U
Zilanti M, et al: JUM 1995
If
the cervical length is deviated
(defined as greater than 5mm from
straight) then 2 straight lines should
be used.
Usually a short Cx not deviated
If the cx canal is closed then the only
measurement that is necessary is
the cervical length .
Don’t Trace to Measure the Cervical Length
If the
is > 3 mm,
use two
measures
SHOULD
BE REPORTED TO THE
PATIENT
REPEAT IN 1 – 2 WEEKS
OPTION OF CERCLAGE
BED REST / RESTRICTED ACTIVITY
DISCUSSED
DIFFERENT FOR MULTIPLE
GESTATION ?
PTD
IN CURRENT PREGNANCY
HISTORY OF PTD
INDEPENDENT OF OTHER RISK
FACTORS: RACE , Ffn , BLEEDING ,
BACTERIAL VAGINOSIS ,BMI
,CONTRACTIONS
RANDOMIZED
61 SINGLETON
FUNNEL 1.5 cms WIDE 1.8 cms DEEP
McDONALD vs OBSERVATION
NO DIFFERENCE IN OUTCOME
MORE PTD LESS THAN 34 WEEKS ,
LESS DELIVERIES BEFORE 28
WEEKS IF CERCLAGE
Randomized
study of prophylactic
cerclage in twins showed no benefit
GOI 1982 13:55
Cerclage in multiples with shortened
cervix also showed no benefit ajog
2002 186 634
CX
LENGTH IS NORMALLY
DISTRIBUTED
LENGTH INVESELY RELATED TO PTD
RISK
T –Y –V –U AT ALL GESTATIONAL
AGES
LENGTH MORE IMPORTANT THAN
FUNNEL
CX SONOGRAPHY NOT EQUAL TO PTD
PREVENTION
Between 22 and 30 weeks of gestation, the length of the
cervix is
described by a normal bell-shaped curve
5th percentile at 20 mm
10th percentile at 25 mm
50th percentile at 35 mm
90th percentile at 45 mm
Cervical Effacement = T Y V U
T
Y
V
U
Zilanti M, et al: JUM 1995
PRACTICE
MAKES PERFECT
PELIC EXAM INITIALLY
COAT THE EXTERNAL OS WITH GEL
MATERNAL BLADDER EMPTY
ANTERIOR FORNIX THEN
INTERNAL OS
EXTERNAL OS NEXT
FUNDAL PRESSURE 10 – 15 SEC
MOST
AUTHORS FEEL THEY ARE
ADDITIVE IN HELPING PREDICT
PRETERM BIRTH
HIGH RISK WOMEN WITH A CX
LENGTH OF < 25mm AND A
POSITIVE fFN HAVE A 65 % CHANCE
OF DELIVERY AT < 35 WEEKS IAMS
AJOG 1998;178:1035-1040
ULTRASOUND
AND fFN TESTING MAY
BE HELPFUL IN DETERMINING
WOMEN AT HIGH RISK FOR PTD
HOWEVER THEIR CLINICAL
USEFULNESS MAY REST WITH THEIR
NEGATIVE PREDICTIVE VALUE
Debris:
Mobile
Variable
Echogenic
Material
Near the
Cervix
Intramniotic debris ( Sludge )
Sonographic
finding of hyperechoic
matter floating in the amniotic fluid
Possible cellular material related to
infection or inflammation
A high correlation with poorer
prognosis
A
Cx length <25 mm between 16
and 24 weeks has been shown to be
the most reliable threshold for a
increased risk of preterm delivery.
Two Randomized trials
(cerclage for short cervix)
Rust study:(2001) 113
women all with either Cx
length 2.5 or funneling
25%
47% had preterm birth
and 20% had a prior 2nd
trimester loss and there
were 8 rescue cerclages,
and 16 % had twins
Used indocin for all patients
Cerclage in this group did
not change the preterm
delivery rate
Althuisius’ study: (2001)
was smaller 35 women
with a good history for
Cx insufficiency
Short Cx only were
excluded
74 % had a prior
preterm birth and 46 %
had a 2nd trimester loss
and only 2 rescue
cerclages
Indocin used in cerclage
arm only
Cerclage did show a
decreased preterm
delivery rate
Cerclage for prior preterm delivery
in women with a short cervix Owens
1014
2009
screened
302 randomized
Decreased the previable rate <24
weeks
Birth rate less than 35 weeks was
unchanged unless the cervix was
especially short <15 mm