What is the most reliable ultrasound parameter for assessment of fetal head descent?

The aims of this study were, first, to establish the agreement between digital and ultrasound assessment of occipital position and, second, to evaluate the repeatability of the measurements of head direction, angle of the middle line, progression distance and angle of progression in women in the second stage of labor. Digital examination and then transabdominal ultrasound examination was performed on 50 women in the second stage of labor to determine the fetal occipital position. We also obtained three-dimensional (3D) blocks of the fetal head by transperineal sonography, and two experts in 3D ultrasound measured head direction, angle of the middle line, progression distance and angle of progression. Intraclass correlation coefficients with 95% CIs, and Bland-Altman analysis, were used to evaluate intraobserver and interobserver repeatability of measurements. The fetal head position, determined by ultrasound examination, was occiput anterior in 33 (66%) cases and occiput lateral in 17 (34%) cases. Vaginal digital examination failed to identify the correct fetal head position by more than 45° in 33 (66%) cases. All four 3D ultrasound measurements were reproducible but the progression angle had the highest intraclass correlation coefficient for the same observer (0.94; 95% CI, 0.90-0.97) and for two different operators (0.84; 95% CI, 0.73-0.91). The progression angle was also the measurement for which smaller limits of agreement (LOA) were found in the Bland-Altman test, performed to calculate the intraobserver (bias 0.9; LOA, - 9.2 to 11.1%) and interobserver (bias 1.5; LOA, - 15.4 to 18.3%) variability. Digital pelvic examination for determining the fetal head position during labor is not accurate. The most reproducible of the 3D measurements for progression of the fetal head in labor is the progression angle.

Molina FS ，Terra R ，Carrillo MP ，Puertas A ，Nicolaides KH ... -  《-》

Measurement of fetal head descent using the 'angle of progression' on transperineal ultrasound imaging is reliable regardless of fetal head station or ultrasound expertise.

Dückelmann AM ，Bamberg C ，Michaelis SA ，Lange J ，Nonnenmacher A ，Dudenhausen JW ，Kalache KD ... -  《-》

Agreement between two- and three-dimensional transperineal ultrasound methods in assessing fetal head descent in the first stage of labor.

To study intraobserver repeatability and intermethod agreement between two- (2D) and three-dimensional (3D) transperineal ultrasound methods in assessing fetal head descent during the first stage of labor. Fetal head descent was measured with transperineal ultrasound as the fetal head-perineum distance and the angle of progression in 106 primiparous women with prolonged first stage of labor. A single obstetrician performed all the scans, and another obstetrician analyzed the acquired 2D images and 3D volumes, blinded to clinical assessments and labor outcome. Intraobserver repeatability and intermethod agreement between 2D and 3D methods were analyzed. The repeatability coefficient was ± 4.1 mm in 2D acquisitions and ± 1.7 mm in 3D acquisitions of fetal head-perineum distance. The intraclass correlation coefficients (ICC) were 0.94 for 2D and 0.99 for 3D measurements. The angle of progression repeatability coefficients were ± 6.7° using 2D and ± 5.7° using 3D ultrasound and ICCs were 0.91 and 0.94, respectively. The intermethod ICC for fetal head-perineum distance in 2D vs 3D acquisitions was 0.95 and for angle of progression it was 0.93; the intermethod 95% limits of agreement were - 5.8 mm to + 7.2 mm and - 8.9° to + 13.7°, respectively. Cohen's kappa for 2D vs 3D acquisitions was 0.85 using 40 mm as a cut-off level for fetal head-perineum distance and 0.79 using 110° as cut-off level for angle of progression. For one ultrasound operator the intraobserver repeatability and agreement between 2D and 3D ultrasound methods in prolonged first stage of labor were good. Given that 2D methods are simpler to learn and can be analyzed quickly online, 2D equipment might therefore be preferred in the labor room.

Torkildsen EA ，Salvesen KÅ ，Eggebø TM 《-》

Three-dimensional ultrasound in monitoring progression of labor: a reproducibility study.

The aim of this study was to evaluate the intraobserver and interobserver reproducibility of measurements, obtained from stored ultrasound volumes, related to fetal head progression in the birth canal. From January to September 2009, serial ultrasound volumes were obtained from women in labor, stored and separately evaluated by two different operators using the SonoVCAD™ labor software. Volumes were aligned using the pubic bone and the urethra as references. In the sagittal plane of the pelvis, the following data were calculated: head progression distance (the distance between the infrapubic line and the lowest part of the fetal skull), head direction (the angle between the infrapubic line and the major longitudinal axis of the fetal head) and head progression angle (the angle between the longitudinal axis of the pubic bone and a line joining the lowest edge of the pubis to the lowest convexity of the fetal skull). In the transverse plane, the angle formed by the midline with the anteroposterior axis of the maternal pelvis (midline angle) was also measured. For each measurement, intraobserver and interobserver reproducibility was determined. We analyzed 30 ultrasound volumes. For all parameters, interobserver variation was significantly higher than intraobserver variation. Reproducibility was good for all parameters, except for the midline angle. Among the different ultrasound measurements, the progression angle presented the highest reproducibility. Measurements obtained from stored ultrasound volumes to assess fetal head progression in the second stage of labor have good reproducibility, with progression distance and progression angle being the most reproducible parameters.

Ghi T ，Contro E ，Farina A ，Nobile M ，Pilu G ... -  《-》

The "occiput-spine angle": a new sonographic index of fetal head deflexion during the first stage of labor.

Fetal head "attitude" (relationship of fetal head to spine) in the first stage of labor may have a substantial impact on labor outcome. The diagnosis of fetal head deflexion traditionally is based on digital examination in labor, although the use of ultrasound to support clinical diagnosis has been recently reported. The aims of this study were: (1) to quantify the degree of fetal head deflection via the use of sonography during the first stage of labor; and (2) to determine whether a parameter derived from ultrasound examination (the occiput-spine angle) has a relationship with the course and outcome of labor. This was a prospective multicentric, cross-sectional study conducted at the Maternity Unit of the University of Bologna and Parma from January 2014 to April 2015. A nonconsecutive series of women with uncomplicated singleton pregnancies at term gestation (37 weeks or more) were submitted to transabdominal ultrasound during the first stage of labor. If fetal position was occiput anterior or transverse, the angle between the fetal occiput and the cervical spine (the occiput-spine angle) was sonographically obtained on the sagittal plane. The measurements of the occiput spine-angle were performed offline by 2 operators who were blinded to the labor outcome. The intra- and interobserver reproducibility and the correlation between the occiput-spine angle and the mode of delivery were evaluated. A total of 108 pregnant women were recruited, 79 of which underwent a spontaneous vaginal delivery and 29 were submitted to obstetric intervention (19 cesarean delivery and 10 instrumental vaginal deliveries). The mean value of the occiput-spine angle measured in the active phase of the first stage was 126° ± 9.8° (SD). The occiput-spine angle measurement showed a very good intraobserver (r = 0.86; 95% confidence interval [95% CI] 0.80-0.90) and a fair-to-good interobserver (r = 0.64; 95% CI 0.51-0.74) agreement. The occiput-spine angle was significantly narrower in women who underwent obstetric intervention (cesarean or vacuum delivery) due to labor arrest (121° ± 10.5° vs 127° ± 9.4°, P = .03). Multivariable logistic regression analysis showed that narrow occiput-spine angle values (OR 1.08; 95% CI 1.00-1.16; P = .04) and nulliparity (OR 16.06; 95% CI 1.71-150.65; P = .02) were independent risk factors for operative delivery. A larger occiput-spine angle width (i.e., >125°) showed to be significantly associated with a shorter duration of labor (hazard ratio = 1.62; 95% CI 1.07-2.45; P = .02). We described herein the "occiput-spine angle," a new sonographic parameter to assess fetal head deflection during labor. Fetuses with smaller occiput-spine angle (<125°) are at increased risk for operative delivery.

Ghi T ，Bellussi F ，Azzarone C ，Krsmanovic J ，Franchi L ，Youssef A ，Lenzi J ，Fantini MP ，Frusca T ，Pilu G ... -  《-》