Cervical length for

Preterm birth

preventionSociety for Maternal-Fetal

Medicine, 2016

Prof. Aboubakr

ElnasharBenha University Hospital

Egypt

ABOUBAKR ELNASHAR

CONTENTS

1.CLINICAL SIGNIFICANCE OF A

SONOGRAPHICALLY SHORT CERVIX

2.TRANSABDOMINAL OR TRANSVAGINAL

ULTRASOUND

3.STEPS FOR PROPER CERVICAL LENGTH

MEASUREMENT

4.WHEN TO ASSESS CLDURING PREGNANCY

5.CERVICAL LENGTH SCREENING

6.PREVENTION

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PTB

2/3 are spontaneous

recurrence risks are high

Few tests are available to predict which pregnancies

will deliver preterm

TV cervical length (CL) measurement

an important clinical tool to identify women at high

risk for PTB

allow for interventions to prevent, delay, or prepare

for PTB.

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1. CLINICAL SIGNIFICANCE OF A

SONOGRAPHICALLY SHORT CERVIX

Women with a history of a prior spontaneous PTB

account for:

10% of all births < 34 weeks of gestation.

Mid-trimester CL assessment by TVS:

the best clinical predictor of spontaneous PTB.

Short CL

20-30 mm

Depending on

the population studied

gestational age of assessment

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Short CL

irrespective of prior pregnancy history

has been consistently and reproducibly associated

with an elevated risk of spontaneous PTB across

different gestational age cutoffs and multiple patient

populations

Short CL with a history of a prior spontaneous PTB

at the highest risk of PTB(Iams JD, Berghella, 2010)

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2. Transabdominal or transvaginal ultrasound

TVS:

safe

gold standard’ for measurement CL.

TV vs TA:

highly reproducible

unaffected by maternal obesity, cervical position,

and shadowing from fetal parts

more sensitive

low interobserver variation rate: 5-10%.

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3. STEPS FOR PROPER CERVICAL LENGTH MEASUREMENT

1. Ensure patient has emptied her bladder.

2. Prepare the cleaned probe using a probe cover.

3. Gently insert the probe into the patient’s vagina.

4. Guide the probe into the anterior fornix.

5. Obtain a sagittal, long-axis image of the entire cervix.

6. Remove the probe until the image blurs and then reinsert

gently until the image clears (this ensures you are not using

excessive pressure)

7. Enlarge the image so that the cervix occupies two thirds of the

screen.

8. Ensure both the internal and external os are seen clearly.

9. Measure the cervical length along the endocervical canal

between the internal and external os.

10. Repeat this process twice to obtain 3 sets of images/

measurements.

11. Use the shortest best measurement.

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Schematic representation of transvaginal ultrasonographic

cervical measurements

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Transabdominal ultrasound

Full bladder: compression and artificial lengthening of the cervix.

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Transvaginal ultrasound image of the cervix

cervical length, 38.7 mm

the lower uterine segment (arrows) is still closed and should not

be included in the cervical length.ABOUBAKR ELNASHAR

Transvaginal ultrasound image of short cervix (20.6 mm).

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Transvaginal ultrasound image of short cervix

(9.3 mm) with funneling and amniotic fluid

sludge (arrow).

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Transvaginal ultrasound image showing dilated internal

(solid arrow) and external (dashed arrow) ora.

Note cervical length (closed portion of cervix) cannot be measured

in such cases.ABOUBAKR ELNASHAR

Transvaginal ultrasound image of cervix showing

echogenic lines of cervical cerclage (arrow) at level of internal

os.

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4. WHEN TO ASSESS CL DURING PREGNANCY

Between 16 and 24 w.

Prior to 16 w1. the lower uterine segment is underdeveloped: challenging

to distinguish this area from the endocervical canal

2. first and early second trimester CL had not consistently

shown adequate predictive value of CL measurement for

preterm birth.

Beyond 24weeks1. interventions (cerclage, vaginal progesterone) used 24 w

as the upper gestational age limit for screening and

initiation of therapies or interventions

2. Provide limited clinical value and there is absence of data

to suggest it improves outcomes.

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5. CERVICAL LENGTH SCREENING

The approach to CL screening varies based on patient

characteristics and risk factors.

I. Women with a prior spontaneous PTB

SMFM and ACOG, 2012 guidelines

women with a prior spontaneous PTB undergo CL

screening with TVS.

Performed (every 1-2 w as determined by the

clinical situation)

from 16 until 24 w. (GRADE 1A)

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The issue of universal TV CL screening of singleton

gestations without prior PTB for the prevention of PTB

remains an object of debate.

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II. Other special situations

1. History of treatment for cervical dysplasia

There is insufficient evidence to support additional

screening for women with, LEEP or cold knife cone

for cervical dysplasia.

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2. Multiple gestation

Available data does not indicate adequate clinical

benefit

3. Preterm PROM

insufficient data to suggest clinical benefit.

4. Placenta previa (grade 2B)

No prospective studies testing a management

strategy based on CL

insufficient data to suggest a proven clinical

benefit

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5. After cerclage placement

Neither overall CL nor length below the

stitch correlate well with outcomes

No additional tt for a short cervix after cerclage (e.g.

reinforcement suture does

not improve outcomes)

Insufficient data for benefit

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ABOUBAKR ELNASHAR

Maternal –Fetal medicine Society,

2012

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