Interobserver reliability of digital and endovaginal ultrasonographic cervical length measurements

doi:10.1016/S0002-9378(97)70282-5

American Journal of Obstetrics and Gynecology

Volume 177, Issue 4, October 1997, Pages 853-858

Presented at the Seventeenth Annual Meeting of the Society of Perinatal Obstetricians, Anaheim, California, January 20-25, 1997.

https://doi.org/10.1016/S0002-9378(97)70282-5 Get rights and content

Abstract

OBJECTIVE: Our purpose was to prospectively evaluate the interobserver reliability of digital and endovaginal ultrasonographic cervical length measurements.

STUDY DESIGN: Forty-three women were recruited from our antepartum clinic to participate in this study. Two independent and blinded digital cervical examinations were performed by the first author and a second examiner. Instructions were given to estimate the cervical length in millimeters. After micturition endovaginal ultrasonographic cervical length measurements were performed by two independent, blinded registered diagnostic medical sonographers. Cervical lengths were compared with the Student t test and Pearson's correlation coefficient. A κ statistic was calculated for interobserver reliability at three levels of agreement ±1 mm, ±4 mm, and ±10 mm. Data are expressed as means ± SD.

RESULTS: Digital cervical lengths were not different between the two examiners (18.7 ± 4.8 mm, 20.5 ± 6.2 mm) nor between the two ultrasonographic measurements (38.6 ± 6.1 mm, 39.2 ± 5.4 mm). The digital cervical lengths agreed (±1 mm) 35% of the time (R² 0.10, p = 0.02). The endovaginal ultrasonographic measurements agreed (±1 mm) 74% of the time with a stronger correlation (R² 0.53, p = 0.0001). The κ statistic for interobserver variability was marginal for both digital and endovaginal cervical length measurements when agreement was defined as ±1 mm. Endovaginal ultrasonography was significantly more reliable than digital examination when agreement between examiners was defined as either ±4 mm or ±10 mm.

CONCLUSION: Although both digital and endovaginal ultrasonographic cervical length measurements show correlation between examiners, endovaginal ultrasonography is significantly more reliable when agreement is defined as ≥±4 mm. Serial cervical length measurements to predict preterm labor will be enhanced by the interobserver reliability of endovaginal ultrasonography. (Am J Obstet Gynecol 1997;177:853-8.)

Section snippets

Material and methods

The investigation was a prospective observational study of 43 women undergoing digital cervical examination during pregnancy. After approval by the Medical University of South Carolina Institutional Review Board, women 18 to 40 years old with singleton gestations and intact membranes between 12 and 32 weeks were recruited from among those women registering for prenatal care at the McClennan-Banks Ambulatory Care Center. Patients were targeted for recruitment if they were scheduled to have a

Results

A total of 43 women were enrolled and completed participation in the investigation. The demographic characteristics of the study population are presented in Table I.

The mean digital cervical length of examiner A was 18.7 ± 4.8 mm, which was not significantly different (p = 0.09) from the mean digital cervical length of 20.5 ± 6.7 mm estimated by examiner B. Similarly, there were no significant differences (p = 0.52) in the mean ultrasonographic cervical length measurements between technologist

Comment

Considerable work has been done to identify risk factors for preterm labor and delivery. Unfortunately, most risk assessment schemes have achieved only limited success.¹ Premature cervical shortening and dilation have both been described as being associated with preterm delivery,2, 3, 4, 7, 8, 9 and serial cervical examination has been recommended as appropriate surveillance for women at risk for preterm birth.1, 2, 3, 4, 13 A persistent concern, however, regarding digital cervical assessment

References (15)

TM Stubbs et al.
The preterm cervix and preterm labor: relative risks, predictive values, and changeover time
Am J Obstet Gynecol
(1986)
JY Phelps et al.
Accuracy and intraobserver variability of simulated cervical dilatation measurements
Am J Obstet Gynecol
(1995)
JD Iams et al.
Cervical competence as a continuum: a study of ultrasonographic cervical length and obstetric performance
Am J Obstet Gynecol
(1995)
HF Andersen et al.
Prediction of risk for preterm delivery by ultrasonographic measurement of cervical length
Am J Obstet Gynecol
(1990)
RP Lorenz et al.
Randomized prospective trial comparing ultrasonography and pelvic examination for preterm labor surveillance
Am J Obstet Gynecol
(1990)
RW. Zalar
Transvaginal ultrasound and preterm prelabor: a non-randomized intervention study
Obstet Gynecol
(1996)
RK. Creasy
Preterm labor and delivery

There are more references available in the full text version of this article.

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Cervical length measurement at 35–37 weeks and risk of Caesarian section in nulliparous women
2020, Gynecologie Obstetrique Fertilite et Senologie
Fetal fibronectin test for threatened preterm delivery 48h after admission: Cost-effectiveness study
2019, European Journal of Obstetrics and Gynecology and Reproductive Biology
Citation Excerpt :
Early discharge after a negative fFN test thus appeared to be a safe option. Ultrasound measurement of cervical length at admission made it possible to select high-risk women for PTD, but the difference of the mean cervical length between the fFN-positive and fFN-negative test groups appeared to be very small (<1–3 mm) and within the range of the observed inter- and intra-observer variability [21,22]. Therefore, the fFN test did not appear to be redundant with this parameter in our study.
The aim of this work was to assess the cost-effectiveness of the fetal fibronectin (fFN) test at 48 h after admission for threatened preterm delivery to promote early discharge.
Before-and-after study to calculate the incremental cost-effectiveness ratio (ICER). Patients were enrolled 48 h after admission in a tertiary care centre for threatened preterm delivery between 24⁺⁰ and 34⁺⁶ weeks. fFN testing was performed. During the first period, physician was blinded to fFN test and discharge occurred after apparent reduced symptomatology at physician’s discretion. During the second period, fFN test was revealed to physician and discharge was immediately proposed to negative test patients. The costs considered in this analysis were the direct medical costs from the hospital perspective: costs of hospitalisation, treatment, and imaging procedures. The efficacy criterion selected was the number of deliveries at 7 and at 14 days after admission for threatened preterm delivery.
The study included 178 pregnant patient, 99 during the first period (July 2008-October 2009) and 79 during the second (March 2010-February 2012). The lengths of hospital stays were shorter during the second period, with more than 50% of women discharged home between 48 and 72 h (p < 0.0001) resulting in a cost-saving of 76 051 euros. The number of deliveries at 7 and at 14 days was similar between the two periods.
The fFN test at 48 h after admission supported early discharge and was safe and cost-effective.
Predictors of preterm birth
2018, Best Practice and Research: Clinical Obstetrics and Gynaecology
Cervical length (CL) measured by transvaginal ultrasound examination (TVUE) best identifies the risk for preterm birth (PTB). It identifies women at risk who can benefit from corticosteroids or in utero transfer. Early screening improves effectiveness of tocolysis. It reduces iatrogenicity and cost. In preterm premature rupture of membranes (PPROM), CL is devoid of infectious risk and predicts duration of the latency phase but not the risk of perinatal sepsis.
Asymptomatic women at risk should be screened at a 2-week interval starting from 16 to 18 weeks, up to 24 weeks. CLs <10th centile are at risk of PTB, especially with decrease in CL after 16 weeks. Repeat ultrasound improves predictive values. Stable CL calls for term delivery. Funneling does not improve predictivity of CL. In twin pregnancies, CL reduces unnecessary interventions. In symptomatic women, fetal fibronectin performs less than CL. Its combination with inconclusive CL has not emerged productive through randomized controlled trials (RCTs), and studies with homogeneous management for preterm labor (PTL) suggest that up to 15% of unjustified hospitalizations and treatment could be avoided.
Association between change in cervical length and spontaneous preterm birth in twin pregnancies
2017, American Journal of Obstetrics and Gynecology
There is a lack of consensus on the optimal transvaginal cervical length for determining risk for spontaneous preterm birth in twin pregnancies. Change in transvaginal cervical length over time may reflect early activation of the parturition process, as has been demonstrated in singleton pregnancies. The association between change in transvaginal cervical length and the risk for spontaneous preterm birth has not yet been described in the population of women with diamniotic twin pregnancies.
Our primary objective is to determine whether rate of change in transvaginal cervical length in the midtrimester is associated with spontaneous preterm birth in twin gestations. Our secondary objective is to describe parameters for identifying patients at increased risk for spontaneous preterm birth based on change in transvaginal cervical length over time.
This is a retrospective cohort of serial transvaginal cervical length performed for twin pregnancies at a single institution from 2008 through 2015. Women with diamniotic twin pregnancies who had transvaginal cervical length measurements at 18 and 22 weeks’ gestation and outcome data available were included. Logistic regression was used to determine the relationship between the rate of change in transvaginal cervical length and the risk for the primary outcome of spontaneous preterm birth <35 weeks as well as spontaneous preterm birth <32 weeks.
In all, 527 subjects met inclusion criteria for this study. The average rate of change in transvaginal cervical length for patients with spontaneous preterm birth <35 weeks was –0.21 cm/wk (SD 0.27) vs –0.10 cm/wk (SD 0.24) for patients who delivered ≥35 weeks (P < .01). The rate of change in transvaginal cervical length was associated with spontaneous preterm birth <35 weeks when controlling for initial transvaginal cervical length and other important risk factors for spontaneous preterm birth. Results for spontaneous preterm birth <32 weeks were similar. This association remained significant when the rate of weekly change was treated as a dichotomous variable based on an apparent inflection point in the risk for spontaneous preterm birth: women with rapid change in transvaginal cervical length, ≥–0.2 cm/wk, had 3.45 times the odds of spontaneous preterm birth as those with less rapid change (95% confidence interval, 2.15–5.52) when controlling for initial transvaginal cervical length.
Change in transvaginal cervical length in the midtrimester is associated with spontaneous preterm birth, and therefore protocols for serial transvaginal cervical length measurement can provide the clinician with information to identify at-risk patients. A decrease of ≥0.2 cm/wk of transvaginal cervical length identifies patients at increased risk for spontaneous preterm birth <35 weeks.
Prediction of preterm delivery in symptomatic women (preterm labor)
2016, Journal de Gynecologie Obstetrique et Biologie de la Reproduction
Évaluer les outils de prédiction d’accouchement prématuré spontané en cas de menace d’accouchement prématuré.
Recherche bibliographique dans les bases de données Medline et Cochrane et les recommandations de sociétés savantes internationales. Sélection des études réalisées sur une population de femmes en situation de menace d’accouchement prématuré.
La menace d’accouchement prématuré est une situation clinique survenant entre 22 et 36 SA + 6 jours, dans laquelle sont observées des modifications cervicales et des contractions utérines, évoluant spontanément ou non vers un accouchement prématuré (accord professionnel). Les contractions utérines peuvent être détectées par la tocométrie et par la patiente elle-même. La fréquence des contractions utérines ne permet pas de prédire avec fiabilité un accouchement prématuré spontané (NP3). Les modifications cervicales peuvent être appréciées par la mesure échographique de la longueur de col et par le toucher vaginal (score de Bishop). La longueur du col est significativement corrélée au risque d’accouchement prématuré spontané (NP1). Les seuils de 15 mm et de 25 mm sont les plus pertinents pour respectivement prédire et écarter un risque d’accouchement prématuré spontané à 48 heures et à 7 jours (accord professionnel). Chez les patientes symptomatiques, la mesure échographique systématique de la longueur de col à l’admission n’est pas associée à une réduction significative du taux d’accouchement prématuré spontané (NP3). L’évaluation clinique du col utérin (score de Bishop) par le toucher vaginal est également un paramètre performant pour la prédiction d’un accouchement prématuré spontané (NP2). Plus le score de Bishop est élevé, plus le risque d’accouchement prématuré spontané est important (NP3). Il n’est pas possible de recommander l’emploi d’un outil plus qu’un autre (échographie du col ou toucher vaginal) en situation de menace d’accouchement prématuré (grade B). Cependant, du fait de l’excellente valeur prédictive négative de la mesure échographique du col, et d’une moindre variabilité interobservateur, il est proposé de mesurer par échographie la longueur cervicale du col avant de décider d’un transfert in utero pour menace d’accouchement prématuré (accord professionnel). Le dépistage de la fibronectine fœtale chez les patientes en situation de menace d’accouchement prématuré a une excellente valeur prédictive négative pour prédire l’absence d’accouchement prématuré spontané à 48 heures et à 7 jours. (NP2). La détection de la fibronectine fœtale chez les patientes en menace d’accouchement prématuré ne permet cependant pas de définir une stratégie permettant de réduire le taux d’accouchement prématuré spontané (NP2) et n’est donc pas recommandée (accord professionnel).
Les outils de prédiction d’un accouchement prématuré spontané en cas de menace d’accouchement prématuré sont performants mais leur usage ne permet pas de réduire le taux d’accouchement prématuré spontané. La valeur prédictive négative élevée de ces outils (mesure échographique du col, détection de la fibronectine fœtale dans les voies génitales) constitue un atout dans le choix de la prise en charge des femmes en situation de menace d’accouchement prématuré (transfert in utero, corticothérapie).
To evaluate the predictors of spontaneous preterm birth in case of preterm labor.
Literature search in Medline and Cochrane databases and recommendations of international societies. Selection of studies in symptomatic women (with preterm labor).
Preterm labor is defined as a clinical situation occurring between 22 and 36 weeks + 6 days, in which cervical changes are observed associated with uterine contractions, evolving spontaneously or not to preterm delivery (Professional consensus). Uterine contractions can be detected by the cardiotocometry and by the patient herself. Uterine contractions frequency does not reliably predict spontaneous preterm birth (NP3). Cervical modifications may be appreciated by ultrasonographic measurement of cervical length and vaginal examination (Bishop score). Cervical length is significantly correlated with the risk of spontaneous preterm birth (NP1). The 15 and 25 mm thresholds are the most relevant to respectively predict and rule out spontaneous premature birth at 48 hours and 7 days (professional consensus). In symptomatic patients, routine ultrasonographic measurement of cervical length at admission is not associated with a significant reduction of spontaneous preterm birth rate (NP3). Clinical evaluation of the cervix (Bishop score) by vaginal examination is an effective parameter for the prediction of preterm birth (NP2). The higher the Bishop score, the higher the risk of preterm birth (NP3). It is not possible to recommend the use of a tool more than another (cervix ultrasound versus vaginal examination) in women experiencing preterm labor (grade B). However, due to the excellent negative predictive value of cervical ultrasound measurement and the lower interobserver variability, we suggest to perform a cervical ultrasonographic measurement before an in utero transfer for preterm labor (professional consensus). Screening for fetal fibronectin in the genital tract of patients with preterm labor has an excellent negative predictive value for predicting the absence of spontaneous preterm birth at 48 hours and 7 days (NP2). Nevertheless, its use in symptomatic women is not associated with a reduction of preterm birth rate (NP2) and is therefore not recommended (professional consensus).
Predictors of preterm birth in women with preterm labor are effective but do not allow a reduction of the preterm birth rate. The high negative predictive value of these predictors (Bishop score, ultrasound measurement of the cervix, fetal fibronectin detection in the genital tract) is an asset in the choice of an appropriate management in women with preterm labor (in utero transfer or corticosteroids).
Elastography of cervix to predict delay from induction to delivery
2014, Gynecologie Obstetrique et Fertilite
Le déclenchement du travail pour raisons médicales est devenu une pratique courante. Le score de Bishop reste la méthode de référence pour évaluer la maturité du col utérin et prédire la durée du déclenchement. L’élastographie est une méthode objective pour apprécier la tonicité des tissus. Ainsi, nous avons cherché à évaluer la valeur prédictive de l’élastographie de contrainte (strain elastography) du col utérin pour prédire le délai d’accouchement après déclenchement parmi des patientes avec un score de Bishop < 6.
L’élastographie a été réalisée immédiatement avant de débuter le déclenchement par prostaglandine parmi des grossesses singletons > 36 SA. Les patientes recevaient 50 μg de misoprostol intravaginal, répété après 6 heures en l’absence de contractions utérines régulières et douloureuses et si le score de Bishop était inférieur à 6. Une deuxième évaluation élastographique était réalisée immédiatement avant la seconde administration de misoprostol. À chaque examen, une cartographie couleur du col était réalisée : l’échelle de couleur allant du bleu, qui caractérise une substance dure, au rouge, qui caractérise une substance molle, en passant par le vert, et le jaune. L’élastographie était considérée comme positive lorsque la berge antérieure du col présentait une zone rouge. Nous avons recherché la valeur prédictive de ce critère sur un accouchement dans les 24 heures.
L’élastographie a été réalisée parmi 48 patientes. Douze patientes ayant accouché par césarienne pour une cause autre que l’échec de déclenchement ont été exclues de l’analyse. Parmi les 36 patientes ayant eu une évaluation élastographique avant déclenchement, 20 ont eu un second examen élastographique avant la seconde administration de misoprostol. La sensibilité, spécificité, valeurs prédictives positive (VPP) et négative (VPN) de l’élastographie réalisée avant le déclenchement sur l’accouchement dans les 24 heures ont été de 40 %, 27,3 %, 55,6 % et 16,7 %, respectivement. La sensibilité, spécificité, VPP et VPN de l’élastographie réalisée avant la seconde administration de misoprostol ont été de 64,3 %, 16,7 %, 64,3 % et 16,7 %, respectivement.
L’élastographie cervicale qualitative est peu prédictive du délai d’accouchement parmi les patientes devant bénéficier d’une maturation du col par prostaglandines.
Induction of labor for medical indications has become a routine practice. To date, the Bishop score remains as the standard method to predict the duration of induced labor. Elastography is an objective method of assessing the relative consistency of tissues. Therefore, we sought to assess strain elastography of cervix to predict delay from induction to delivery in pregnant women with a low Bishop score.
Ultrasound elastography was immediately performed before induction of labor for medical indications among patients with a singleton pregnancy at > 36 weeks of gestation and a Bishop score < 6. Patients received 50 μg of misoprostol intravaginally, repeated 6 hours later if regular painful uterine contractions had not started. A second ultrasound elastography was also performed 6 hours after starting the induction before the second dose of misoprostol if regular painful uterine contractions had not started. At each examination, a color map from blue (hardest tissue) to red (softest tissue) was produced. The cervical elastography was considered as positive if at least one part of its anterior wall was red. We assessed the predictive value of elastography on vaginal delivery within 24 hours. Patients delivering by cesarean section were excluded from this study.
Elastography was initially performed in 48 patients. Twelve patients delivering by cesarean section after induction of labor were excluded, leading to 36 patients evaluated in this study. Among these 36 patients with elastography performed before induction of labor, 20 had a second elastography before the second dose of misoprostol. Sensibility, specificity, positive predictive value (PPV) and negative predictive value (NPV) of elastography performed before induction of labor on vaginal delivery within 24 hours were 40%, 27.3%, 55.6%, and 16.7%, respectively. Sensibility, specificity, PPV and NPV of elastography performed before the second dose of misoprostol were 64.3%, 16.7%, 64.3% and 16.7%, respectively. Among the 8 patients with red color occurring on the second cervical color map, sensibility, specificity, PPV and NPV were 83.3%, 0%, 62.5%, and 0%.
Qualitative cervical elastography is a poor predictor for delay from induction to delivery in pregnant women with a low Bishop score.

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^☆: From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Medical University of South Carolina.

^☆☆: Reprints not available from the authors.

^★: 0002-9378/97 $5.00 + 0 6/6/84416

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Interobserver reliability of digital and endovaginal ultrasonographic cervical length measurements☆,☆☆,★

Abstract

Section snippets

Material and methods

Results

Comment

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Obstet Gynecol

Preterm labor and delivery