Screening for spontaneous preterm birth by cervical length and shear-wave elastography in the first trimester of pregnancy.

BACKGROUND: First-trimester cervical length for the prediction of spontaneous preterm delivery remains controversial. A better method for the measurement of the first-trimester cervical length and additional cervical ultrasound parameters for the identification of women at high risk for spontaneous preterm delivery are needed. OBJECTIVE: This study aimed to compare the predictive value of cervical length measured by 2 different methods in the first trimester of pregnancy to predict spontaneous preterm delivery and to explore the potential value of first-trimester cervical shear-wave elastography for the prediction of spontaneous preterm delivery. STUDY DESIGN: This was a prospective study in unselected singleton pregnancies at 11+0 to 13+6 weeks' gestation. Cervical length was measured by the following 2 methods in the base-cohort population: (1) a linear distance between the 2 ends of the glandular area around the endocervical canal (single-line method: cervical length-s) and (2) a sum of the linear distance from the internal os to the greatest cervical curvature and the linear distance from this point to the external os (2-line method: cervical length-t). In a substudy, cervical shear-wave elastography scores for 9 regions of interest (inner, middle, and external parts of anterior lip, endocervical canal, and posterior lip) in midsagittal plane were also obtained by transvaginal ultrasonography. The screening performance of the first-trimester cervical length measured by the 2 different methods for the prediction of spontaneous preterm delivery was assessed by receiver operating characteristics curve analysis. The areas under the curves were compared using a DeLong test. The predictive performance of a soft cervix (mean elastography scores with multiple of median <5th, 10th, 15th, 20th, and 25th percentile) for spontaneous preterm delivery was also determined. RESULTS: Among a total of 2316 included pregnancies, spontaneous delivery at <37 and <34 weeks' gestation occurred in 111 cases (4.8%) and 20 cases (0.9%), respectively. In the total study population, when compared with the term delivery group, the median cervical length-t was shorter in women with spontaneous delivery at <34 weeks' gestation (36.9 mm vs 35.1 mm; P=.015), but there was no clear correlation for cervical length-s. Receiver operating characteristics curves demonstrated that cervical length-t achieved better performance in predicting spontaneous delivery at <34 weeks' gestation (area under the curve, 0.658 vs 0.573; P<.01) than cervical length-s. The best combined model to predict spontaneous delivery at <34 weeks' gestation was provided by cervical length-t and history of preterm delivery (area under the curve, 0.692). In the substudy, a soft cervix with a mean elastography scores multiple of median <10th percentile had a relative risk of 7.8 (95% confidence interval, 2.1-28.6) for spontaneous delivery at <34 weeks' gestation; the detection rate was 44.4% at a false-positive rate of 9.0%. CONCLUSION: The 2-line approach provides a better estimate of the actual first-trimester cervical length and achieves better performance as a screening tool for spontaneous preterm delivery at <34 weeks' gestation than the conventional measurement. A soft cervix as determined by shear-wave elastograpthy in the first trimester is associated with an increased risk for subsequent spontaneous preterm delivery.

Prediction of spontaneous preterm birth by cervical length in the first trimester of pregnancy: Comparison of two measurement methods.

INTRODUCTION: Our objectives were to compare the single-line and two-line methods of cervical length measurement in the first trimester of pregnancy and to evaluate the potential value of the first trimester cervical length measured by the two methods in predicting spontaneous preterm birth. MATERIAL AND METHODS: This was a prospective study in singleton pregnancies at 11+0 to 13+6  weeks of gestation. Cervical length was measured by two methods: (i) a linear distance between the two ends of the glandular area around the endocervical canal (single-line method) and (ii) a sum of a linear distance from the internal os to the greatest cervical curvature and a linear distance from this point of the cervix to the external os (two-line method). The screening performance of the first trimester cervical length measured by the two different methods for the prediction of spontaneous preterm delivery was assessed by receiver-operating characteristics (ROC) curve analysis. The areas under the ROC (AUROC) were compared by De Long test. RESULTS: A total of 1484 consecutive singleton pregnancies were included in this study. Spontaneous preterm delivery at <37 and <32 weeks occurred in 75 cases (5.1%) and 12 cases (0.8%), respectively. The median cervical length measured by the single-line method was significantly shorter than that by the two-line method (33.5 vs 36.5 mm, p < .001). Compared with the term delivery group, the median cervical length measured by the two-line method was shorter in women with spontaneous delivery at <32 weeks of gestation (36.5 vs 33.6 mm, p < .01). No significant difference in the median cervical length measured by the single-line method was detected between the spontaneous preterm delivery and term delivery groups. Receiver-operating-characteristic curves demonstrated that cervical length measured by the two-line method achieved better performance in predicting spontaneous delivery at <32 weeks compared with the single-line method (AUROC: 0.72 vs 0.61, p < .01). CONCLUSIONS: We have demonstrated that the first trimester cervical length, measured by the two-line approach, holds promise as a potential screening tool for early spontaneous preterm delivery.

Shear-wave sonoelastographic assessment of cervix in pregnancy.

INTRODUCTION: The aim of this study was to investigate the differences in shear-wave sonoelastography (SWS) scores between the different parts of cervix, explore the association between the cervical SWS scores with cervical length and evaluate repeatability of the measurement of cervical SWS scores. MATERIAL AND METHODS: This was a prospective study performed in women with singleton pregnancy at 11-13+6 (n = 676), 16-20+6 (n = 364), 21-24+6 (n = 338) and 28-32+6 weeks (n = 304). The SWS scores were obtained at the inner, middle and external parts of the cervix, using a transvaginal ultrasound approach. RESULTS: The SWS scores of the inner cervix were significantly higher than the measurements acquired at the middle and external parts (all P < .001). At 21-24+6 and 28-32+6 weeks, most regions of interest demonstrated a very weak positive correlation with cervical length (r = .125 to r = .299). In comparison with nulliparous women, parous women without prior preterm birth had higher SWS scores of the inner and middle parts of the cervix at 16-20+6 and 21-24+6 weeks. All regions of interest showed good intra- and inter-observer agreement. CONCLUSIONS: The assessment of the cervical SWS scores is highly reproducible. The stiffness of the cervix demonstrates a gradient that decreases from the inner part to the external part and a very weak positive correlation with cervical length.