VBAC Uterine Scar Measurement Info_ January 2011

7/5/12 VBAC Uterine Scar Measurement Info: January 2011

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F R I D A Y, J A N U A R Y 1 4 , 2 0 1 1

More exchanges with Dr. Rozenberg

Here are other questions I sent Dr. Rozenberg that relate to this

measurement, and his responses. They prov ide additional

information on the measurement as well as his thoughts as to its

helpfulness in predicting uterine rupture. Start at the bottom and

work y our way up.

#4 - Second Response from Dr. Rozenberg

Dear [Me]

1)"There have been other studies on this topic [other than y ours]

and not all are so favorable".

> I disagree with this assertion. I enclose y ou a recent rev iew of

studies about this topic. all are corresponding; however, most

have biases.

2)"A uterine scar could be thick at 37 weeks and thin at 39 weeks.

For that matter, it could be thick at the onset of labor but thin two

hours later."

> I agree with it. however, our study showed that when the low

uterine segment was thick around 37 weeks, the risk of uterine

rupture during a trial of labor was very low. Moreover, most of

thin low uterine segments are not pathologic. In all, in order to

help y ou to understand :

- when the low uterine segment is thick around 37 weeks, it is

usually strong

- when the low uterine segment is thin around 37 weeks, y ou can

not correctly predict the issue.

I hope that my explanations will help y ou to understand. Give me

news when y ou will be delivered (or before if y ou have any other

questions)

sincerely

T H I S B L O G D O E S N O T C O N S T I T U T E

M E D I C A L A D V I C E !

Nothing in this blog is to be

construed as medical adv ice. As

with any thing else, please consult a

licensed health care professional

regarding all things discussed in

this blog. Note specifically that the

information prov ided on uterine

segment measurements is not to be

construed as adv ice from a health

care professional, but simply as

information a woman can present

to her health care professional in

the context of deciding upon or

planning a VBAC. And as should be

obvious, uterine segment

measurements are not 100%

reliable in predicting uterine

rupture, so a VBAC attempt should

be undertaken only after a women

fully understands all of the risks

and benefits and with the

knowledge that there is no way to

know with absolute surety whether

she will be in the small percentage

of women who will develop a

uterine rupture or other

complication.

B L O G A R C H I V E

▼ 2011 (3)

▼ January (3)

More exchanges with Dr.

Rozenberg

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patrick

#3 - Second Em ail to Dr. Rozenberg

Dear Dr. Rozenberg,

A few months ago I emailed y ou about y our studies regarding the

connection between the thickness of the LUS and a patient's

chances of uterine rupture during a VBAC attempt. I believe, at

the time, I emailed and thanked y ou for y our prompt and

informative responses, and I'd like to do so again now. If y ou don't

mind indulging me one last time, I'd like to ask y ou one more

question.

After corresponding with y ou, I asked an American doctor, Bruce

Flamm, who has published books and articles on VBAC over here,

why most American doctors don't perform a LUS measurement on

their VBAC patients. His response was this: "There have been other

studies on this topic [other than y ours] and not all are so

favorable. A uterine scar could be thick at 37 weeks and thin at 39

weeks. For that matter, it could be thick at the onset of labor but

thin two hours later."

My question is, do y ou agree with this? I am just a lay person, of

course, but I have read many other studies (accessed through

online journal banks like Pub Med) and they all suggest that

women with a prior cesarean section scar, on average,

consistently have thinner LUS segments than women with

unscarred uteruses. So, I'm tempted to think his response is

incorrect, but I wanted y our opinion.

Thanks again,

[Me]

#2 - Dr. Rozenberg's Response

Dear Leigha

> My question is, do y ou still believe this finding is accurate?

Y es, I do and we practice this examination in our department

before deciding on the mode of delivery with our patients

>If so, why don't more doctors do sonograms to measure this

when they have a VBAC candidate?

I think that most obstetricians feel uncomfortable with the

perspective of legal suits in rare cases of uterine rupture in case of

How to perform lower uterine

segment measurement

Studies on ultrasonographic

measurement of the low...



trial of labour and prefer to perform repeat Cesarean Sections.

Even in France, the LUS measurement is rarely performed.

Sincerely y ours

Patrick

#1 - My first em ail to Dr. Rozenberg

Dear Dr. Rozenberg,

My name is [Me].... I am writing y ou because I had a cesarean

section with my first child in December 2004 because she was

breech, and I am contemplating getting pregnant again soon. I

have been researching in-depth the possibility of hav ing a VBAC

with my next baby . In doing his search, I found an article y ou

wrote in 1996 on how measurements of a woman's lower uterine

segment in the third trimester can predict whether she will suffer a

uterine rupture during a trial of labor. Specifically , y our article

showed that women with a measurement of over 3.5mm are

almost guaranteed not to rupture. This is of great interest to me

because, like many other potential VBAC candidates, I am afraid

to try a VBAC for fear of hav ing a uterine rupture. My question is,

do y ou still believe this finding is accurate? If so, why don't more

doctors do sonograms to measure this when they have a VBAC

candidate? What can I say to my doctor (who I don't think does

this ty pe of measurement) to get him to do it when I'm pregnant?

I'm

pretty convinced by y our findings that I want this ty pe of

measurement done but it just doesn't seem to be done that

commonly over here.

Any advice/encouragement/information is appreciated.

[Me]

POSTED BY LEIGHA AT 12:52 PM 2 COM M ENTS:

How to perform lower uterine segment

measurement

Here is a description of how one doctor performs a uterine

segment measurement. This information is from Dr. Patrick

Rozenberg, the author of the best studies on the subject. He does it

v ia transabdominal ultrasound (the kind that goes over y our

belly ), but my sonographer actually did it v ia transvaginal



ultrasound because she thought she could get better readings that

way (and, in fact, a later study suggested that she was correct).

I measured a 4mm when my sonographer did it. Dr. Rozenberg's

1996 study on this measurement suggested a cut-off of 3.5mm;

because I had a higher measurement than this, I felt comfortable

going forward with my VBAC attempt.

Here's the link to the description of the 1996 study .

Description of how Dr. Rozenberg perform s the

m easurem ent:

From: [Dr. Rozenberg]

To: [Me]

Sent: Wednesday , August 1 , 2007 12:28:00 PM

Subject: RE how to perform ultrasonographic measurement of the

lower uterine segment

Transabdominal examination

Between 36 and 38 weeks

Full bladder (v isualization of the whole LUS)

Sagittal sections of the LUS

Measure of the thinnest zone (upper third of the LUS)

Calipers at the interface of the bladder and the amniotic fluid-

decidua

(on-to-on)

LUS in an almost horizontal plane

3 measurements (smallest value chosen)

sincerely

PR(See attached file: SI.5.3.jpg)



POSTED BY LEIGHA AT 11:43 AM NO COM M ENTS:

Studies on ultrasonographic measurement of the

lower uterine segment

These are all of the studies I could find on the national medical

studies database, http://www.pubmed.com/, related to the

ultrasonographic measurement of the lower uterine segment on

patients with a prior cesarean section and its success in predicting

uterine rupture/safety of trial of labor. If y ou are an information

junkie like me, these might be helpful in y our decision as to

whether or not to discuss with y our health care professional the

possibility of hav ing this measurement performed.

J Obstet Gy naecol Can. 2010 Apr;32(4):321-7 .

Sonographic lower uterine segm ent thickness and risk of

uterine scar defect: a sy stem atic review.

Jastrow N, Chaillet N, Roberge S, Morency AM, Lacasse Y , Bujold

E.

Department of Obstetrics and Gy naecology , Centre Hospitalier

Universitaire Sainte-Justine, Faculty of Medicine, Université de

Montréal, Montreal QC.

OBJECTIVE: To study the diagnostic accuracy of sonographic

measurements of the lower uterine segment (LUS) thickness near

term in predicting uterine scar defects in women with prior

Caesarean section (CS).



DATA SOURCES: PubMed, Embase, and Cochrane Library (1965-

2009).

METHODS OF STUDY SELECTION: Studies of populations of

women with prev ious low transverse CS who underwent third-

trimester evaluation of LUS thickness were selected. We retrieved

articles in which number of patients, sensitiv ity , and specificity to

predict a uterine scar defect were available.

DATA SY NTHESIS: Twelve eligible studies including 1834 women

were identified. Uterine scar defect was reported in a total of 121

cases (6.6%). Seven studies examined the full LUS thickness only ,

four examined the my ometrial lay er specifically , and one

examined both measurements. Weighted mean differences in LUS

thickness and associated 95% confidence intervals between

women with and without uterine scar defect were calculated.

Summary receiver operating characteristic (SROC) analy sis and

summary diagnostic odds ratios (DOR) were used to evaluate and

compare the area under the curve (AUC) and the association

between LUS thickness and uterine scar defect. Women with a

uterine scar defect had thinner full LUS and thinner my ometrial

lay er (weighted mean difference of 0.98 mm; 95% CI 0.37 to 1 .59,

P = 0.002; and 1 .13 mm; 95% CI 0.32 to 1 .94 mm, P = 0.006,

respectively ). SROC analy sis showed a stronger association

between full LUS thickness and uterine scar defect (AUC: 0.84 +/-

0.03, P < 0.001) than between my ometrial lay er and scar defect

(AUC: 0.7 5 +/- 0.05, P < 0.01). The optimal cut-off value varied

from 2.0 to 3.5 mm for full LUS thickness and from 1 .4 to 2.0 for

my ometrial lay er.

CONCLUSION: Sonographic LUS thickness is a strong predictor for

uterine scar defect in women with prior Caesarean section.

However, because of the heterogeneity of the studies we analy zed,

no ideal cut-off value can y et be recommended, which underlines

the need for more standardized measurement techniques in future

studies.

Arch Gy necol Obstet. 2010 Feb 10.

Sonographic assessm ent of lower uterine segm ent at

term in wom en with previous cesarean delivery .

Kushtagi P, Garepalli S.

KMC Quarters Manipal University Campus, Manipal, 57 6104,

India, [email protected].

OBJECTIVE: To correlate lower uterine segment (LUS) thickness



measured by abdominal sonography at term pregnancy with that

measured manually using caliper at cesarean delivery and to find

out minimum LUS thickness indicative of its integrity in women

with prev ious cesarean.

METHODS: In 106 women with prev ious cesarean delivery and 68

with unscarred uterus, abdominal sonographic assessment of LUS

was carried out within a week of delivery . Sonographic

measurements were correlated with manual measurement of

lower flap of LUS using Vernier calipers in 96 of these women (64

with prev ious cesarean and 32 of unscarred uterus) who had

elective cesarean delivery .

RESULTS: Sonographically determined LUS was thinner among

women with prev ious cesarean delivery than in those without

(4.58 SD 1 .05 vs. 4.8 SD 0.8; t = 1 .986; p = 0.04). Women with

vaginal birth after cesarean had thicker LUS than women with

repeat cesarean delivery (4.4 SD 0.97 vs. 4.48 SD 1 .0). The

findings were not influenced by engaged fetal head status or

amount of bladder fullness. Directly measured LUS thickness using

Vernier calipers before delivery of the baby confirmed ultrasound

measurements, but showed smaller differences between them.

There were eight cases with defective uterine scar at cesarean.

LUS thickness at term of 3 mm provided 87 .5% sensitiv ity and

specificity , and was found to have negative predictive value of

98%. But in two of seven cases the actual LUS was not measurable

despite sonographic measurement of 3 mm, and there were two

records of scar dehiscence in those with 3 and 4 mm of LUS

thickness.

CONCLUSION: LUS thickness of 3 mm measured by abdominal

ultrasonography prior to delivery at term in women with prev ious

cesarean is suggestive of stronger LUS but is not a reliable

safeguard for trial of labor.

Am J Obstet Gy necol. 2009 Sep;201(3):320.e1-6.

Prediction of com plete uterine rupture by sonographic

evaluation of the lower uterine segm ent.

Bujold E, Jastrow N, Simoneau J, Brunet S, Gauthier RJ.

Department of Obstetrics and Gy naecology , Faculty of Medicine,

Centre de recherche du Centre hospitalier universitaire de

Québec, Université Laval, Québec, QC, Canada.

[email protected]

OBJECTIVE: The purpose of this study was to establish the validity



of sonographic evaluation of lower uterine segment (LUS)

thickness for complete uterine rupture.

STUDY DESIGN: A prospective cohort study of women with

prev ious cesarean delivery was conducted. LUS thickness (full

thickness and my ometrial thickness only ) was measured between

35 and 38 weeks gestation, and the thinnest measurement was

considered to be the dependent variable. Receiver operating

curve analy ses and logistic regression were used.

RESULTS: Two hundred thirty -six women were included in the

study . Nine uterine scar defects (3 cases of complete rupture

during a trial of labor and 6 cases of dehiscence) were reported.

Receiver operating curve analy ses showed that full thickness of

<2.3 mm was the optimal cutoff for the prediction of uterine

rupture (3/33 vs 0/92; P = .02). Full thickness was also identified

as an independent predictor of uterine scar defect (odds ratio,

4.66; 95% confidence interval, 1 .04-20.91)

CONCLUSION: Full LUS thickness of <2.3 mm is associated with a

higher risk of complete uterine rupture.

Int J Gy naecol Obstet. 2009 Nov;107 (2):140-2. Epub

2009 Aug 13.

Com parison of transabdom inal versus transvaginal

ultrasound to m easure thickness of the lower uterine

segm ent at term .

Marasinghe JP, Senanay ake H, Randeniy a C, Seneviratne HR,

Arambepola C, Dev lieger R.

University Obstetrics and Gy necology Unit, De Soy za Hospital for

Women, Colombo, Sri Lanka. jeevanmarasinghe@y ahoo.com

OBJECTIVE: To compare the accuracy of transvaginal (TVS)

versus transabdominal (TAS) ultrasound to assess the thickness of

the lower uterine segment (LUS).

METHODS: Eighty -three pregnant women admitted for an elective

cesarean delivery were enrolled. LUS thickness was measured

using both TVS and TAS prior to the cesarean. The actual

thickness of the LUS was measured using a sterile metal ruler after

the neonate had been delivered.

RESULTS: Seventeen women had unscarred uteri (20.1%); 41 had

had one prev ious cesarean (49.4%); and 25 had had two prev ious

cesareans (30.1%). Mean thickness of the LUS measured after



delivery was 7 .58+/-1 .3 mm in unscarred uteri; 5.09+/-1 .4 mm

for one cesarean; and 3.92+/-1 .1 mm for two cesareans (P<0.01).

Actual thickness of the LUS showed a significant correlation with

TVS among the total (r(s)=0.89); with unscarred uteri (r(s)=0.68);

with 1 cesarean (r(s)=0.89); and 2 cesareans (r(s)=0.68), while

with TAS the correlations were significant only with the total

(r(s)=0.53) and 2 prev ious cesareans (r(s)=0.63) (P<0.01).

CONCLUSION: TVS is a more accurate method of assessing the

thickness of the LUS compared with TAS.

Ultrasound Obstet Gy necol. 2009 Mar;33(3):301-6.

Lower uterine segm ent thickness m easurem ent in

pregnant wom en with previous Cesarean section:

reliability analy sis using two- and three-dim ensional

transabdom inal and transvaginal ultrasound.

Martins WP, Barra DA, Gallarreta FM, Nastri CO, Filho FM.

Departamento de Ginecologia e Obstetrícia da Faculdade de

Medicina de Ribeirão Preto, Universidade de São Paulo and Escola

de Ultra-sonografia de Ribeirão Preto, Ribeirão Preto, São Paulo,

Brazil. [email protected]

OBJECTIVE: To evaluate the reliability of two- and three-

dimensional ultrasonographic measurement of the thickness of

the lower uterine segment (LUS) in pregnant women by

transvaginal and transabdominal approaches.

METHODS: This was a study of 30 pregnant women who had had at

least one prev ious Cesarean section and were between 36 and 39

weeks' gestation, with singleton pregnancies in cephalic

presentation. Sonographic examinations were performed by two

observers using both 4-7 -MHz transabdominal and 5-8-MHz

transvaginal volumetric probes. LUS measurements were

performed using two- and three-dimensional ultrasound,

evaluating the entire LUS thickness transabdominally and the LUS

muscular thickness transvaginally . Each observer measured the

LUS four times by each method. Reliability was analy zed by

comparing the mean of the absolute differences, the intraclass

correlation coefficients, the 95% limits of agreement and the

proportion of differences < 1 mm.

RESULTS: Transvaginal ultrasound prov ided greater reliability in

LUS measurements than did transabdominal ultrasound. The use

of three-dimensional ultrasound improved significantly the

reliability of the LUS muscular thickness measurement obtained



transvaginally .

CONCLUSIONS: Ultrasonographic measurement of the LUS

muscular thickness transvaginally appears more reliable than

does that of the entire LUS thickness transabdominally . The use of

three-dimensional ultrasound should be considered to improve

measurement reliability .

Gy necol Obstet Fertil. 2005 Dec;33(12):1003-8.

T he counselling of patient with prior C-section.

Rozenberg P.

Departement de gy necologie-obstetrique, centre hospitalier de

Poissy --Saint-Germain, universite Versailles-Saint-Quentin,

France. prozenberg@chi-poissy -st-germain.fr

A trial of labor after prior cesarean delivery is associated with a

greater perinatal risk than is elective repeated cesarean delivery

without labor, although absolute risks are low. Information and

counselling aim to estimate specific risks and to balance these

risks according to indiv idual factors. Therefore, the phy sician has

to answer two questions: (i) which would be the probability of

successful vaginal delivery ? (ii) which would be the risk of uterine

rupture with a trial of labor? The risk factors for failure of trial of

labor are: increased maternal age, obesity , and fetal macrosomia.

The risk factors for uterine rupture are: increased maternal age,

postpartum fever after the prev ious cesarean delivery , short

interdelivery interval, history of at least two prev ious cesarean

deliveries, and a history of classical incision. Conversely , other

factors are of good prognosis: a prior vaginal delivery and,

particularly , a prior VBAC (Vaginal Birth After Caesarean) are

associated with a higher rate of successful trial of labor compared

with patients with no prior vaginal delivery ; ultrasonographic

measurement of the lower uterine segment thickness>3.5 mm has

an excellent negative predictive value for the risk of uterine

defect. Finally , the wish for additional pregnancies following a

cesarean section must be considered as an argument in favour of a

trial of labor after accounting for the increasing risks correlated

with repeated elective cesarean deliveries.

J Obstet Gy naecol Can. 2005 Jul;27 (7 ):67 4-81.

Sonographic m easurem ent of the lower uterine segm ent

thickness in wom en with previous caesarean section.

Cheung VY .

Department of Obstetrics and Gy naecology , North Y ork General

Hospital, Toronto, ON.



OBJECTIVES: To evaluate the accuracy of prenatal sonography in

determining the lower uterine segment (LUS) thickness in women

with prev ious Caesarean section and to assess the usefulness of

measuring LUS thickness in predicting the risk of uterine rupture

during a trial of vaginal birth.

METHODS: Sonographic examination was performed in 102

pregnant women with one or more prev ious Caesarean sections at

between 36 and 38 weeks' gestation to assess the LUS thickness,

which was defined as the shortest distance between the urinary

bladder wall-my ometrium interface and the

my ometrium/chorioamniotic membrane-amniotic fluid interface.

Of the 102 women examined, 91 (89.2%) had transabdominal

sonography only , and 11 (10.8%) had both transabdominal and

transvaginal examinations. The sonographic measurements were

correlated with the delivery outcome and the intraoperative LUS

appearance.

RESULTS: The mean sonographic LUS thickness was 1 .8 mm,

standard dev iation (SD) 1 .1 mm. An intraoperatively diagnosed

paper-thin or dehisced LUS, when compared with an LUS of

normal thickness, had a significantly smaller sonographic LUS

measurement (0.9 mm, SD 0.5 mm, vs. 2.0 mm, SD 0.8 mm,

respectively ; P < 0.0001). Two women had uterine dehiscence,

both of whom had prenatal LUS thickness of < 1 mm. Thirty -two

women (31 .4%) had a successful vaginal delivery , with a mean LUS

thickness of 1 .9 mm, SD 1 .5 mm; none had clinical uterine rupture.

A sonographic LUS thickness of 1 .5 mm had a sensitiv ity of 88.9%,

a specificity of 59.5%, a positive predictive value of 32.0%, and a

negative predictive value of 96.2% in predicting a paper-thin or

dehisced LUS.

CONCLUSIONS: Sonography permits accurate assessment of the

LUS thickness in women with prev ious Caesarean section and

therefore can potentially be used to predict the risk of uterine

rupture during trial of vaginal birth.

Int J Gy naecol Obstet. 2004 Dec;87 (3):215-9.

Ultrasonographic evaluation of lower uterine segm ent

thickness in patients of previous cesarean section.

Sen S, Malik S, Salhan S. Department of Obstetrics and Gy necology ,

Vardhman Mahavir Medical College and Safdarjung Hospital, New

Delhi, India. dr_sumana_sen@y ahoo.com



OBJECTIVE: To evaluate by ultrasonography , the lower uterine

segment thickness of women with a prev ious cesarean delivery

and determine a critical thickness above which safe vaginal

delivery is predictable.

METHODS: A prospective observational study of 7 1 antenatal

women with prev ious cesarean delivery and 50 controls was

carried out. Transabdominal and transvaginal ultrasonography

were used in both groups to evaluate lower uterine segment

thickness. The obstetric outcome in patients with successful

vaginal birth and intraoperative findings in women undergoing

cesarean delivery were correlated with lower segment thickness.

RESULTS: The overall vaginal birth after cesarean section (VBAC)

was 46.5% and VBAC success rate was 63.5%, the incidence of

dehiscence was 2.82%, and there were no uterine ruptures. There

was a 96% correlation between transabdominal ultrasonography

with magnification and transvaginal ultrasonography . The critical

cutoff value for safe lower segment thickness, derived from the

receiver operator characteristic curve, was 2.5 mm.

CONCLUSION: Ultrasonographic evaluation permits better

assessment of the risk of scar complication intrapartum, and could

allow for safer management of delivery .

J Ultrasound Med. 2004 Jul;23(7 ):907 -11; quiz 913-4.

Second-trim ester sonographic com parison of the lower

uterine segm ent in pregnant wom en with and without a

previous cesarean delivery .

Sambaziotis H, Conway C, Figueroa R, Elimian A, Garry D.

Department of Obstetrics, Gy necology , and Reproductive

Medicine, State University of New Y ork Health Sciences Center at

Stony Brook, Stony Brook, New Y ork 117 94, USA.

OBJECTIVE: To compare measurements of the lower uterine

segment during a second-trimester sonographic examination in

women with and without a prev ious cesarean delivery .

METHODS: Women undergoing second-trimester sonographic

examination, 24 with a history of cesarean delivery and 30

control subjects with no history of cesarean delivery , were

recruited for transvaginal sonographic evaluation of the lower

uterine segment with a high-frequency probe. The uterine niche or

prev ious cesarean scar site was defined as a small triangular

anechoic defect in the anterior wall of the uterus. The uterine wall



thickness was measured successively at the level where the

bladder dome meets the lower uterine segment. Measurements

were obtained with cursors at the interface of the urine-bladder

and the amniotic fluid-decidua. The study was approved by the

Institutional Rev iew Board, and P < .05 was considered

significant.

RESULTS: The uterine niche was identified in 14 (58%) of 24

women with a prev ious cesarean delivery . The lower uterine

segment was significantly thinner in women with a prev ious

cesarean delivery compared with control subjects (mean +/- SD,

4.7 +/- 1 .1 versus 6.6 +/- 2.0 mm; P < .001). In the prev ious

cesarean group, the mean lower uterine segment thickness was

similar in the 5 women with 2 cesarean deliveries when compared

with those with 1 cesarean delivery (4.6 +/- 1 .0 versus 4.7 +/- 1 .4

mm; P = .91). In a linear regression model, the only variable

retaining significance in the prediction of uterine wall thickness

was prev ious cesarean delivery (P= .002). Maternal age, parity ,

number of prev ious cesarean deliveries, and gestational age did

not attain significance in the model.

CONCLUSIONS: The lower uterine segment during a second-

trimester sonographic examination is significantly thinner in

women with a prev ious cesarean delivery . Identification of the

scar niche is possible in most of these women.

J Ultrasound Med 23:1441-1447 (2004)

Sonographic Evaluation of the Lower Uterine Segm ent in

Patients With Previous Cesarean Delivery .

Cheung, V., Constantinescu, O., Ahluwalia, B. Department of

Obstetrics and Gy necology , North Y ork General Hospital,

Toronto, Ontario, Canada (V.Y .T.C.); and BSA Diagnostic Imaging,

Toronto, Ontario, Canada (O.C.C., B.S.A.), vcheung@ny gh.on.ca.

Objective. To evaluate the appearance of the lower uterine

segment (LUS) in pregnant women with prev ious cesarean

delivery and to compare the LUS thickness with that in women

with unscarred uteri.

Methods. In a prospective study , sonographic examination was

performed on 53 pregnant women with prev ious cesarean

delivery (cesarean group), 40 nulliparas (nullip-control), and 40

women who had 1 or more childbirths with unscarred uteri

(multip-control) between 36 and 38 weeks’ gestation to assess the

appearance and compare the thickness of the LUS. In the cesarean



group, the sonographic findings were correlated with the delivery

outcome and the intraoperative LUS appearance.

Results. In the cesarean group, 44 patients (83.0%) had a normal-

appearing LUS indistinguishable from that of control groups; 2

patients (3.8%) had an LUS defect suggestive of dehiscence; and 7

patients (13.2%) had thickened areas of increased echogenicity

with or without my ometrial thinning. Although the cesarean

group had a thinner LUS (1 .9 ± 1 .4 mm) when compared with both

the nullip-control group (2.3 ± 1 .1 mm; P > .05) and the multip-

control group (3.4 ± 2.2 mm; P < .001), only the latter difference

achieved statistical significance. One of the 2 patients who had a

sonographically suspected LUS defect had confirmed uterine

dehiscence during surgery . An intraoperatively diagnosed paper-

thin LUS, when compared with an LUS of normal thickness, had

significantly smaller sonographic LUS measurements (1 .1 ± 0.6

versus 2.0 ± 0.8 mm, respectively ; P = .004).

Conclusions. Prior cesarean delivery is associated with a

sonographically thinner LUS when compared with those with

prior vaginal delivery . Prenatal sonographic examination is

potentially capable of diagnosing a uterine defect and determining

the degree of LUS thinning in patients with prev ious cesarean

delivery .

Aust N Z J Obstet Gy naecol. 2000 Nov;40(4):402-4.

Preoperative diagnosis of dehiscence of the lower uterine

segm ent in patients with a single previous Caesarean

section.

Suzuki S, Sawa R, Y oney ama Y , Asakura H, Araki T.

Department of Obstetrics and Gy necology , Nippon Medical

School, Toky o, Japan.

Preoperative diagnoses were checked during surgery in 39

patients who underwent elective repeat Caesarean section with (n

= 20) and without (as control, n = 19) a preoperative diagnosis of

wall dehiscence (thinning) of the lower uterine segment (LUS). All

patients were examined manually and by ultrasonography at 36

weeks gestation before labour. A preoperative diagnosis of wall

dehiscence was made when the wall thickness was less than 2 mm

and/or the patient felt pain and tenderness in the LUS. Surgical

findings of dehiscence were defined as a subperitoneal separation

of the uterine scar in the LUS. The sensitiv ity and specificity of our

ultrasonographic evaluations were found to be 100% and 83% (p <

0.05), respectively . On the other hand, there were no surgical



findings of dehiscence in patients who felt pain and tenderness in

the LUS with a wall thickness greater than 2 mm, nor among those

in the control group.

J Nippon Med Sch. 2000 Oct;67 (5):352-6.

Prediction of uterine dehiscence by m easuring lower

uterine segm ent thickness prior to the onset of labor:

evaluation by transvaginal ultrasonography .

Asakura H, Nakai A, Ishikawa G, Suzuki S, Araki T. Department of

Obstetrics and Gy necology , Nippon Medical School, Sedagi,

Toky o, Japan. asakura [email protected]

OBJECTIVE: Lower uterine segment thickness was measured by

transvaginal ultrasound examination and its correlations with the

occurrence of uterine dehiscence and rupture was examined.

METHODS: The thickness of the muscular lay er of the lower

uterine segment was measured in 186 term grav idas with prev ious

uterine scars and its correlation with uterine dehiscence/rupture

was investigated.

RESULTS: Uterine dehiscence was found in 9 cases or 4.7 %. There

were no cases of the uterine rupture. The thickness of the lower

uterine segment among the grav idas with dehiscence was

significantly less in than those without dehiscence (p< 0.01). The

cut-off value for the thickness of the lower uterine segment was 1 .6

mm as calculated by the receiver operating characteristic curve.

The sensitiv ity was 7 7 .8%; specificity 88.6%; positive predictive

value 25.9%; negative predictive value 98.7 %.

CONCLUSION: Measurement of the lower uterine segment is useful

in predicting the absence of dehiscence among grav idas with

prev ious cesarean section. If the thickness of the lower uterine

segment is more than 1 .6 mm, the possibility of dehiscence during

the subsequent trials of labor is very small.

Obstet Gy necol. 2000 Apr;95(4):596-600.

Predicting incom plete uterine rupture with vaginal

sonography during the late second trim ester in wom en

with prior cesarean.

Gotoh H, Masuzaki H, Y oshida A, Y oshimura S, Miy amura T,

Ishimaru T. Department of Obstetrics and Gy necology , Nagasaki

University School of Medicine, Nagasaki, Japan.

OBJECTIVE: To evaluate the usefulness of serial transvaginal



ultrasonographic measurement of the thickness of the lower

uterine segment in the late second trimester for predicting the risk

of intrapartum incomplete uterine rupture in women with

prev ious cesarean delivery .

METHODS: Serial transvaginal ultrasonography with full bladder

was performed in 37 4 women without prev ious cesarean delivery

(control group) and 348 women with prev ious cesarean delivery

(cesarean group) from 19 to 39 weeks' gestation. The thickness of

the lower uterine segment was measured in the longitudinal plane

of the cerv ical canal.

RESULTS: The thickness of the lower uterine segment decreased

from 6.7 +/- 2.4 mm (mean +/- standard dev iation [SD]) at 19

weeks' gestation to 3.0 +/- 0.7 mm at 39 weeks' gestation in the

control group, but the thickness was more than 2.0 mm

throughout this period in each control subject. In the cesarean

group, the thickness decreased from 6.8 +/- 2.3 mm at 19 weeks'

to 2.1 +/- 0.7 mm at 39 weeks' gestation and was significantly

thinner than that of the control group after 27 weeks' gestation (P

<.05). Eleven of 12 women (91%) with lower uterine segment less

than the mean control - 1 SD in the late second trimester had a

very thin lower uterine segment at cesarean delivery with fetal

hair being v isible through the amniotic membrane, ie, incomplete

uterine rupture. In 17 of 23 women (7 4%) with lower uterine

segment less than 2.0 mm in thickness within 1 week (4 +/- 3 day s)

before repeat cesarean delivery , intrapartum incomplete uterine

rupture developed.

CONCLUSION: Transvaginal ultrasonography is useful for

measurement of the uterine wall after prev ious cesarean delivery .

Eur J Obstet Gy necol Reprod Biol. 1999 Nov;87 (1):39-45.

T hickness of the lower uterine segm ent: its influence in

the m anagem ent of patients with previous cesarean

sections.

Rozenberg P, Goffinet F, Philippe HJ, Nisand I. Department of

Gy necology and Obstetrics, Poissy Hospital, University Paris V,

France. gy nobs.poissy @wanadoo.fr

OBJECTIVE: To determine how ultrasound measurement of the

lower uterine segment affects the decision about delivery for

patients with prev ious cesarean sections (CS) and what are the

consequences on cesarean section rates and uterine rupture or

dehiscence.



PATIENTS: 198 patients: all women with a prev ious CS who gave

birth in our department during 1995 and 1996 to an infant with a

gestational age of at least 36 weeks and who underwent ultrasound

measurement of their lower uterine segment (95-96 study group),

compared with a similar population from 1989 to 1994 whose

measurements were not prov ided to the treating obstetrician.

RESULTS: Among the patients with one prev ious CS, the vaginal

delivery rate did not differ significantly during the two periods

(7 0.3% for the 89-94 study period vs. 67 .9% for the 95-96 study

period, P=0.53), but the 95-96 study group experienced a

significant increase in the rate of elective CS, compensated by a

reduction in the rate of emergency CS (6.3% and 23.4%,

respectively , for the 89-94 study period vs. 11 .9% and 20.1% for

the 95-96 study period, P=0.01). There was a very significant

increase in the rate of vaginal delivery for the 95-96 study period

among patients with two prev ious CS (26.7 % vs. 8.0% for the 89-

95 study period, P=0.01). The lower uterine segment was

significantly thicker among women with a trial of labor than

among those with an elective CS (4.5+/-1 .4 mm compared with

3.8 +/- 1 .5 mm; P=0.006); and the trial of labor group contained

significantly fewer women with a lower uterine segment

measurement less than 3.5 mm than did the elective CS group

(24.0% compared with 56.6%; P<0.001). Two patients (0.8%)

were found to have a defect of the uterine scar, a rate significantly

lower than that observed in the early group (3.9%, P=0.03).

CONCLUSIONS: Ultrasound measurement of the lower uterine

segment can increase the safe use of trial of labor, because it

prov ides an additional element for assessing the risk of uterine

rupture.

Minerva Ginecol. 1999 Apr;51(4):107 -12.

T ransvaginal ultrasonic evaluation of the thickness of

the section of the uterine wall in previous cesarean

sections.Montanari L, Alfei A, Drovanti A, Lepadatu C, Lorenzi D,

Facchini D, Iervasi MT, Sampaolo P.

Istituto di Clinica Ostetrica e Ginecologica, Universita degli Studi,

IRCCS San Matteo, Pav ia, Italy .

BACKGROUND: The aim of this study is to evaluate accuracy of

transvaginal sonographic examination of the lower uterine

segment in pregnant women with prev ious cesarean section.



METHODS: Sixty -one pregnant women between 37 and 40 weeks

of gestation, with prev ious cesarean section underwent

transvaginal ultrasonography . Wall thickness of the lower uterine

segment, the length of cerv ix , dilation of the isthmus uteri were

measured. On the basis of the surgical findings (in 53 patients) and

outcome of the trial of labor (in 8 patients) a Score was assigned to

the pregnant women: Score 1 to the women who had good healing

or a trial of labor without complications; Score 2 to the women

with a thin or discontinued scar and in case of threatened rupture

of the uterus in the trial of labor.

RESULTS: The mean thickness of the lower uterine segment is 3.82

mm +/- 0.99 mm. The Score 1 group shows a mean thickness of

4.2 mm +/- 2.5 mm, and the Score 2 group a mean thickness of 2.8

mm +/- 1 .06 mm. The transvaginal sonographic examination

provides a sensitiv ity and a specificity respectively of 100 and

7 5%, for a thickness cut-off of 3.5 mm, and a positive and negative

predictive values of 60.7 % and 100% respectively .

CONCLUSIONS: The transvaginal sonographic evaluation of the

lower uterine segment improves therefore the obstetrical

decision-making regarding the trial of labor in women with

prev ious cesarean section.

T ohoku J Exp Med. 1997 Sep;183(1):55-65.

Ultrasonographic evaluation of lower uterine segm ent to

predict the integrity and quality of cesarean scar during

pregnancy : a prospective study .

Qureshi B, Inafuku K, Oshima K, Masamoto H, Kanazawa K.

Department of Obstetrics and Gy necology , School of Medicine,

University of the Ry uky us, Okinawa, Japan.

A prospective randomized study was conducted to measure the

serial thickness of the lower uterine segment (LUS) by

transvaginal ultrasonography in a control group of 80 women

having no history of uterine surgery and in a study group of 43

women having a history of prev ious cesarean section (C/S). In the

study group, more than 2 mm of thickness of the LUS was

considered as good healing and less than 2 mm of thickness as

poor healing. After serial sonographic examination, the women

with good healing were given trial for labor unless an obstetrical

indication for C/S existed. The appearance of the LUS during

surgery was compared with antenatal ultrasonographic

assessment by direct inspection. Twenty two (7 9%) of 28 women

with a well healed scar had trial labor with the result that 46% had



a successful vaginal birth without any uterine rupture of

dehiscence. Eight women with poor healing all had elective C/S.

Seven women with a 2 mm LUS thickness were indiv idually

categorized for delivery mode. Two of those women delivered

vaginally . The LUS was found to be thin to translucent in these

later two groups. Two mm or less as a criterion for poor healing

had the sensitiv ity and specificity of 86.7 % and 100%

respectively . The positive predictive value was 100% and the

negative predictive value was 86.7 %. Ultrasonographic evaluation

is effective in predicting the quality of a uterine scar and in

differentiating the risk group of probable uterine rupture from the

non risk group.

J Clin Ultrasound. 1996 Sep;24(7 ):355-7 .

Sonographic evaluation of the wall thickness of the lower

uterine segm ent in patients with previous cesarean

section.

Tanik A, Ustun C, Cil E, Arslan A.

Radiology Department, 19 May is University , Samsun, Turkey .

In pregnant women with a history of cesarean section, wall

thickness of the lower uterine segment may help determine the

risk and safety of vaginal delivery . Determination of wall thickness

may help identify the potential risk of uterine rupture in pregnant

women who do not wish to have another cesarean section or who

are not eligible for surgery due to other sy stemic disorders. In this

study , 50 pregnant women with prev ious cesarean sections were

evaluated with ultrasound preoperatively , and measurements of

the lower uterine segment wall thickness were compared with

intraoperative assessment of uterine thinning. These findings

correlated highly with each other (sensitiv ity : 100%; specificity :

82% positive predictive value: 87 %; negative predictive value:

100%), suggesting the reliability and safety of ultrasound in

evaluating uterine wall thickness.

Zhonghua Fu Chan Ke Za Zhi. 1994 Aug;29(8):458-60,

508-9.

Detection of uterine scar defect during pregnancy by

ultrasonics.

Y ang TZ, Li WZ.

Second Affiliated Hospital, West China University of Medical

Science, Chengdu.

B ty pe ultrasonography was used to observe the formation of

lower uterine segment in 7 1 primigrav ide and the status of lower



uterine segment scar in 31 multiparae with prev ious cesarean

section (CS), from the 33 to 41 gestational week. Results showed

that the lower uterine segments was formed in all 102 cases after

the 33rd week. Compared with the primigrav ide, the lower uterine

segment in the CS group was longer, thinner and not as wide after

the 37 th gestational week. Defective scars of the lower uterine

segment were found in 7 cases of the CS group and 2 of them were

diagnosed as threatened dehiscence owing to the fetal sac

protruding from the scar site. Condition of all these cases were

confirmed during operation. The present study suggested that B

ultrasonic scar can be a helpful and noninvasive method for

detecting scar defect in the lower uterine segment following CS.

Lancet. 1996 Feb 3;347 (8997 ):281-4.

Ultrasonographic m easurem ent of lower uterine

segm ent to assess risk of defects of scarred uterus.

Rozenberg P, Goffinet F, Phillippe HJ, Nisand I.

Department of Obstetrics and Gy naecology , Centre Hospitalier

Intercommunal, Leon Touhladjian, Poissy , France.

BACKGROUND: Ultrasonography has been used to examine the

scarred uterus in women who have had prev ious caesarean

sections in an attempt to assess the risk of rupture of the scar

during subsequent labour. The predictive value of such

measurements has not been adequately assessed, however. We

aimed to evaluate the usefulness of sonographic measurement of

the lower uterine segment before labour in predicting the risk of

intrapartum uterine rupture.

METHODS: In this prospective observational study , the

obstetricians were not told the ultrasonographic findings and did

not use them to make decisions about ty pe of delivery . Eligible

patients were those with prev ious caesarean sections booked for

delivery at our hospital. 642 patients underwent ultrasound

examination at 36-38 weeks' gestation, and were allocated to four

groups according to the thickness of the lower uterine segment.

Ultrasonographic findings were compared with those of phy sical

examination at delivery .

FINDINGS: The overall frequency of defective scars was 4.0% (15

ruptures, 10 dehiscences). The frequency of defects rose as the

thickness of the lower uterine segment decreased: there were no

defects among 27 8 women with measurements greater than 4.5

mm, three (2%) among 17 7 women with values of 3.6-4.5 mm, 14

(10%) among 136 women with values of 2.6-3.5 mm, and eight



(16%) among 51 women with values of 1 .6-2.5 mm. With a cut-off

value of 3.5 mm, the sensitiv ity of ultrasonographic measurement

was 88.0%, the specificity 7 3.2%, positive predictive value 11 .8%,

and negative predictive value 99.3%.

INTERPRETATION: Our results show that the risk of a defective

scar is directly related to the degree of thinning of the lower

uterine segment at around 37 weeks of pregnancy . The high

negative predictive value of the method may encourage

obstetricians in hospitals where routine repeat elective caesarean

is the norm to offer a trial of labour to patients with a thickness

value of 3.5 mm or greater.

Arch Gy necol Obstet. 1991;248(3):129-38.

Ultrasound exam ination of caesarean section scars

during pregnancy .

Fukuda M, Shimizu T, Ihara Y , Fukuda K, Natsuy ama E, Mochizuki

M.

Fukuda Ladies Clinic, Ako, Japan.

Two hundred and sixteen transverse caesarean section scars were

examined sonographically near term by a conventional method

(17 5 scars) and a new method (41 scars). The new method

consisted of obtaining a transabdominal longitudinal scan by the

conventional method and also by a 3M conductor, a

transabdominal frontal scan to give a surface v iew of the scar, and

transperineal and transvaginal longitudinal scans. The new

method was used from 16 weeks of gestation onwards. Of 41 scars

scanned by the new method, 31 showed good healing, being more

than 2 mm in thickness throughout; 10 scars showed poor healing

with a thickness of less than 2 mm and loss of continuity . Of 31

patients with good healing, 8 delivered vaginally and the

remaining 23 patients had repeat caesarean sections for other

obstetric indications. All patients with ultrasound ev idence of

poor healing had repeat caesarean sections. At operation the

thickness of the lower uterine segment was measured with

ophthalmic calipers. There were 4 false negative results (4/83:

4.8%) and 1 false positive result (1/43: 2.3%) with conventional

ultrasound and no false positives or false negatives with the new

method.

Arch Gy necol Obstet. 1988;243(4):221-4.

Exam ination of previous caesarean section scars by

ultrasound.

Fukuda M, Fukuda K, Mochizuki M.



Fukuda Ladies Clinic, Ako, Japan.

We examined 84 lower segment caesarean section scars by

ultrasonography near term. Seventy scars showed good healing

with a thickness of the lower uterine segment of more than 3 mm;

14 scars showed poor healing with a thickness of less than 2 mm

and loss of continuity . Among 7 0 patients with good healing, 24

patients delivered vaginally but the remaining 46 patients have

had repeat caesarean sections for other obstetric indications.

Intraoperative findings in these 46 patients were as follows: Grade

I (no thinning of the lower uterine segment), 42; Grade II

(thinning and loss of continuity of the lower uterine segment but

fetal hair not v isible), 4; Grade III (thinning of the lower uterine

segment and fetal hair v isible), 0. Fourteen patients with poor

healing had repeat caesarean sections. Intraoperative findings in

these 14 patients were as follows: Grade I, 0; Grade II, 9; Grade

III, 5. These results indicate that ultrasound examination detect

thinning of the lower uterine segment and may help to determine

management.

Obstet Gy necol. 1988 Jan;7 1(1):112-20.

Ultrasound diagnosis of defects in the scarred lower

uterine segm ent during pregnancy .

Michaels WH, Thompson HO, Boutt A, Schreiber FR, Michaels SL,

Karo J.

Department of Obstetrics and Gy necology , Prov idence Hospital,

Southfield, Michigan.

A prospective study was begun using ultrasound to diagnose

defects in the lower uterine segment. Seventy patients were

examined and delivered by cesarean section, including 58 at risk

because of prev ious cesarean section and 12 nulliparous controls

not at risk. Of the at-risk patients, 12 had confirmed defects, for an

incidence of 20.7 %. All the controls were normal. The false-

positive rate for at-risk patients was 7 .1%, and the positive and

negative predictive values were 92.3 and 100%, respectively . For

the diagnosed cases, the sonographic lower uterine segment

seemed to form earlier (P less than .01) and was thinner (P less

than .01) than that in the negative cases or the controls. Although

our study design was observational and did not allow us to test the

performance of the lower uterine segment when a defect was

found, we discuss the use of a three-stage classification sy stem to

assist in identify ing sonographically detected defects in a future

trial of labor protocol. We conclude that sonographic surveillance

is a reliable and practical means of evaluating the lower uterine



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