Dynamic cervical change during real-time ultrasound: prospective characterization and comparison in patients with and without symptoms of preterm labor

Contractions of the lower uterine segment during transvaginal ultrasound cervical length: incidence, significance, proper measurement, and management

An accurate transvaginal ultrasound cervical length is paramount to obtain the best prediction for preterm birth. Transvaginal ultrasound cervical length should be optimally obtained when a lower uterine segment contraction is not seen. For universal transvaginal ultrasound cervical length screening at approximately 20 weeks of gestation, the options are to do the transvaginal ultrasound soon after bladder void (lower uterine segment contractions present in 16%-43% of this approach) or to wait until the end of the anatomy scan (ideally within 30 minutes after bladder voiding) to decrease the chance of a lower uterine segment contraction. If the lower uterine segment contraction persists even after waiting up to 20 minutes or more, only the true transvaginal ultrasound cervical length should be reported. In particular, in patients with a previous spontaneous preterm birth, if the lower uterine segment contraction persists, the transvaginal ultrasound cervical length can be repeated in ≤7 days even in the presence of a normal (>25 mm) cervical length. Similar to a blood pressure cuff that must be of the right size for proper blood pressure measurement and a glucometer that must be properly calibrated, screening with transvaginal ultrasound cervical length should only be performed following a proper and standardized technique, including avoiding as much as feasible the presence of lower uterine segment contractions.

Is real-time dynamic cervical shortening predictive of preterm birth?- A case control study

OBJECTIVES

We aimed to assess the risk of preterm birth in those with real-time dynamic cervical shortening.

METHODS

A retrospective matched case-control study. The study group comprised all women with dynamic cervical shortening (≥4 mm) noted from 24 to 34 weeks of gestation during 2010-2017 at a university hospital. Two control groups of women were established by matching the minimal and maximal cervical length measured, as well as age, parity, gestational age, history of spontaneous preterm birth, symptoms of preterm labor, and delivery year.

RESULTS

Data from 339 women were analyzed, 113 with dynamic cervical shortening comprised the study group, and two groups with 113 women each, matched for the minimal and maximal cervical lengths measured comprised the control groups. Rates of spontaneous preterm birth rate at <37 weeks (32.7% vs. 15.9%; OR [95% CI]: 2.60 (1.36, 4.87), p = .004) and <35 weeks (15.9% vs. 5.3%; OR [95% CI]: 3.38 (1.29, 8.86), p = .013) were significantly higher among those with dynamic cervix than among the control group matched for the maximal cervical length, and comparable to the control group matched for the minimal cervical length. The negative predictive values of cervical length for preterm birth occurrence at various cutoff values were lower in those with dynamic cervix.

CONCLUSIONS

The minimal cervical length measured should be used to guide patient management when dynamic cervix is noted. In the setting of dynamic cervical change, the value of cervical length as a negative predictor of preterm birth is limited.

Racial and social predictors of longitudinal cervical measures: the Cervical Ultrasound Study

OBJECTIVE

To evaluate whether the racial and socioeconomic disparities are present in adverse cervical parameters, and, if so, when such disparities develop.

STUDY DESIGN

A prospective cohort study was conducted. 175 women with a prior preterm birth had up to four endovaginal ultrasounds between gestational weeks 16 and 24 (Cervical Ultrasound Trial of the MFMU). Each sociodemographic factor (race/ethnicity, marital status, insurance funding and education) was examined as a predictor of short cervix or U/funnel shape, using multiple logistic and linear regression. Changes in the cervical length and shape across pregnancy and after pressure were also examined.

RESULTS

The strongest associations were seen between race and government-funded insurance and short cervix and U shape per funneling (race and length <25 mm per funnel: adjusted odds ratio (OR) 5.52, 2.24 to 13.63; government-funded insurance and length <30 mm per funnel: adjusted OR 3.10, 1.34 to 7.15). Changes in cervical length were not associated with sociodemographics.

CONCLUSION

African-American race and, to a lesser extent, insurance funder, are associated with cervical length and shapes that have been associated with preterm birth, and those properties are present largely early in pregnancy.

Amniotic fluid "sludge" is an independent risk factor for preterm delivery

OBJECTIVE

To determine the prevalence and the clinical significance of amniotic fluid "sludge" (AFS) in asymptomatic patients at low and high risk for spontaneous preterm delivery.

METHOD

A prospective cohort study was conducted on 195 singleton pregnancies at low or high risk for preterm birth (PTB) between the 16th and 26th weeks. Cervical length (CL) <25 mm and the presence of AFS were evaluated. The risk for preterm delivery before 28, 32, 35 and 37 weeks were determined according to the presence of AFS, CL < 25 mm and history of high risk for PTB. Stepwise logistic regression was performed to compare variables.

RESULTS

AFS was an independent risk factor for PTB < 35 weeks (OR: 3.08, 95% CI: 1.13-8.34, p = 0.027) but not for PTB < 28, 32 and 37 weeks. CL < 25 mm was an independent risk factor for PTB < 28, 32 and 35 but not for PTB < 37 weeks. High risk for PTB was not found as an independent risk factor for PTB.

CONCLUSION

AFS is an independent risk factor for PTB before 35 weeks.

Is dynamic cervical shortening during symptomatic contractions predictive of preterm delivery in patients with a normal baseline cervical length?

OBJECTIVE

The purpose of this study was to determine whether dynamic cervical change in symptomatic patients with a normal baseline cervical length (CL; >or=30 mm) is predictive of preterm delivery (PTD).

METHODS

A prospective observational study was performed in 120 symptomatic patients between 23 and 34 weeks' gestation. Patients underwent standardized CL sonography with contraction monitoring, and CL measurements were recorded each minute for approximately 10 minutes. Initial and minimum CLs as well as the presence of dynamic change were assessed for prediction of PTD.

RESULTS

Forty-seven patients (39.2%) had dynamic cervical change and delivered at a mean gestational age +/- SD of 37.1 +/- 2.7 weeks compared to 38.7 +/- 1.5 weeks for those without dynamic change (P < .01). A larger proportion of those with dynamic change delivered before 37 weeks (43% versus 15%; P < .01) and before 35 weeks (19% versus 0%; P < .01). Multivariable logistic regression analysis showed that dynamic cervical change was predictive of PTD, but not independently of the minimum CL. Statistical analyses were completed using the Student t test, chi(2) test, Fisher exact test, Wilcoxon rank sum test. and logistic regression as appropriate.

CONCLUSIONS

Although symptomatic patients with a normal baseline CL who have dynamic shortening generally deliver at term, they appear to be at increased risk of PTD.

The value of serial cervical length measurements for the prediction of threatened preterm labour

OBJECTIVES

To assess the predictive performance of cervical length measurement at presentation and 24h later in women with symptoms of preterm labour.

STUDY DESIGN

Cervical length was measured transvaginally at presentation and 24 hours later in 122 women presenting with threatened preterm labour between 23 and 33+6 gestational weeks.

RESULTS

Six women delivered within 1 week of presentation. The sensitivity and specificity of a cervical length <15 mm at admission for delivery within one week was 83.3 and 95.8%, respectively. A reduction of >20% in cervical length 24h after admission predicted 50% of preterm deliveries within 1 week, with a specificity of 92.7%; in combination with cervical length at presentation it did not improve the prediction. The same was observed for birth before 32 weeks (N=9) and birth before 35 weeks (N=15).

CONCLUSIONS

Women with threatened preterm labour and a cervical length of <15 mm at presentation are at high risk of delivering preterm. Cervical change in the following 24 hours does not seem to improve the prediction.

Prevention of preterm birth based on short cervix: symptomatic women with preterm labor or premature prelabor rupture of membranes

The diagnosis of preterm labor (PTL) is challenging, especially in women whose cervical dilatation is <2 cm and who are <80% effaced. In symptomatic women, with threatened PTL in both singletons and twins, transvaginal ultrasound cervical length (CL) identifies a high-risk group that is more likely to be in true PTL, more likely to deliver sooner, and more likely to deliver preterm. The addition of fetal fibronectin improves the predictive accuracy in women whose CL is <30 mm but >15 mm. Transvaginal ultrasound CL can also be performed in the presence of ruptured membranes and predicts latency. Although additional data are needed, the evidence so far suggests that the use of transvaginal ultrasound CL and fetal fibronectin can be used to better identify and manage women with PTL likely to have an imminent preterm delivery, and to avoid interventions in women who would not.

Dynamic cervical length changes: Preliminary observations from 30-minute transvaginal ultrasound recordings

OBJECTIVE

The purpose of this study was to visualize and quantify dynamic changes in the cervix and to study factors influencing cervical length.

METHODS

Eighteen women with a gestational age between 23 and 40 weeks were examined by transvaginal ultrasound during a continuous observation period of 30 minutes.

RESULTS

All women delivered at >34 weeks of gestation, fourteen at term. The overall mean difference between the shortest and longest cervical length during the 30-minute recordings (cervical length variation) was 10.9 mm (range 1.6-26.7 mm). In the presence of fetal movements directed at the cervix, peristaltic movement of the bowel or contractions, cervical length variation was larger than in the absence of these conditions (mean 12.7 mm, range 5.2-26.7 mm and mean 6.1 mm, range 1.6-9.4 mm, respectively; p = 0.03).

CONCLUSIONS

Dynamic changes in cervical length are present at early gestation and long before delivery and can be observed either spontaneously or associated with contractions, fetal movements or peristalsis. These conditions must be considered as pitfalls in cervical length measurement. In critical cases, such as early threatened preterm labor, increases in the frequency and duration of sonographic ultrasound measurements may be helpful to obtain a more reliable estimation of the cervical status.

Cervical length assessment in women with idiopathic polyhydramnios

OBJECTIVE

The aims of the study were to determine cervical length among patients with polyhydramnios and to assess the relationship between the severity of polyhydramnios, cervical length and gestational age at delivery.

PATIENTS AND METHODS

A prospective study was designed including 92 consecutive singleton pregnancies with polyhydramnios between 24 and 40 weeks' gestation. Cervical length was measured using transvaginal sonography. Polyhydramnios was defined when amniotic fluid index (AFI) was equal to or greater than 20 cm. A single sonologist performed all the examinations of the cervical length and the AFI.

RESULTS

The median cervical length and AFI were 37.5 (range, 7-52) mm and 28.8 (range, 20-43) cm, respectively. A significant gradual shortening of the cervical length was observed with advancing gestational age (P=0.027). No significant association was found between AFI and cervical length (P=0.24). A cut-off of 15 mm (n=5) was associated with a significantly lower gestational age at delivery (30+/-2.6 weeks vs. 37.2+/-4.2 weeks, respectively, P<0.001).

CONCLUSIONS

Women with polyhydramnios have a gradual shortening of cervical length with advancing gestational age. However, this finding is not related to the severity of polyhydramnios.

Dynamic cervical change: is real-time sonographic cervical shortening predictive of preterm delivery in patients with symptoms of preterm labor?

OBJECTIVES

To determine prospectively if dynamic cervical change (spontaneous real-time cervical shortening) is predictive of preterm delivery at < 37 weeks' gestation in patients with symptoms of preterm labor.

METHODS

This was a prospective study of patients at 23-34 weeks' gestation who were symptomatic for preterm labor. Patients underwent a 10-min real-time sonographic cervical length assessment with measurements taken at 1-min intervals. The presence or absence of dynamic cervical change, defined as real-time changes in cervical length observable to the naked eye of the sonologist during the examination, was recorded. Gestational age at delivery was obtained from medical records. Preterm delivery was defined as delivery at < 37 weeks' gestation. Dynamic cervical change and initial and minimum cervical lengths were assessed for prediction of preterm delivery.

RESULTS

Seventy-six patients were enrolled, and 66 were available for outcome analysis. Thirty-one patients (47%) exhibited dynamic cervical change. Patients with dynamic change had shorter initial cervical lengths (27 mm vs. 36 mm, P = 0.001), shorter minimum cervical lengths (20 vs. 33 mm, P < 0.001) and larger changes in cervical length during the examination period (10 vs. 4 mm, P < 0.001). In the subgroup of patients with an initial cervical length > 30 mm, those with dynamic change delivered earlier than did those without dynamic change (36.8 vs. 38.6 weeks, P = 0.02), and a higher percentage delivered preterm (27% vs. 11%, odds ratio (OR), 3.0 (0.5-17.0)). Multivariate analysis showed that minimum cervical length was a better predictor of preterm delivery than was initial cervical length.

CONCLUSIONS

Dynamic cervical change occurs frequently in association with shortened cervical length. In patients with longer initial cervical lengths, dynamic change may increase the risk for preterm delivery. When dynamic change is noted in a patient with preterm labor symptoms, use of the minimum cervical length observed may be better compared with initial cervical length for determining preterm delivery risk.

Cervical Sonography in Women with Symptoms of Preterm Labor

In the last few years, ultrasound of the cervix during pregnancy has been the focus of much research. Significant advances have been made in its technique and in understanding the proper role of this procedure in several clinical settings. This article reviews the evidence for the clinical role of transvaginal cervical assessment in women with symptoms of preterm labor.