A new method to assess fetal head descent in labor with transperineal ultrasound.

To assess the feasibility and reproducibility of measuring fetal head station and descent during labor using transperineal ultrasound (TPU) imaging, to compare the evaluation of fetal station through digital examinations with concurrent TPU assessments, and to assess its utility in distinguishing patients whose pregnancy will result in spontaneous vaginal delivery from those who will require operative vaginal delivery or Cesarean section for failure to progress. TPU and digital examinations were performed in 88 term laboring patients with a singleton fetus in cephalic presentation. Using TPU imaging, head descent was quantified by measuring the angle between the long axis of the pubic symphysis and a line extending from its most inferior portion tangentially to the fetal skull. Intraobserver and interobserver variability were calculated using variance component analysis. TPU imaging was used to measure the angle of head descent during the second stage of labor in 23 of the women. Analysis of replicated measurements on 75 subjects, by the same observer at approximately the same time, yielded an average SD (intraobserver variability) of approximately 2.9 degrees for the measurement of angle of head descent on TPU examination. A separate variance component analysis on a subset of 15 assessments for which measurements were repeated by a second observer, with two to four replicate measurements obtained by each, yielded an interobserver error estimate of 1.24 degrees. A significant linear association was found between clinical digital assessments and measurement of angle of head descent by TPU examination (P < 0.001). An angle of at least 120 degrees measured during the second stage of labor was always associated with subsequent spontaneous vaginal delivery. In six pregnancies ending in Cesarean section the mean angle of descent measured at last TPU examination was only 108 degrees. The angle of head descent measured by TPU imaging provides an objective, accurate and reproducible means for assessing descent of the fetal head during labor.

Barbera AF ，Pombar X ，Perugino G ，Lezotte DC ，Hobbins JC ... -  《-》

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 ... -  《-》

Fetal head descent assessed by transabdominal ultrasound: a prospective observational study.

Determining fetal head descent, expressed as fetal head station and engagement is an essential part of monitoring progression in labor. Assessing fetal head station is based on the distal part of the fetal skull, whereas assessing engagement is based on the proximal part. Prerequisites for assisted vaginal birth are that the fetal head should be engaged and its lowermost part at or below the level of the ischial spines. The part of the fetal head above the pelvic inlet reflects the true descent of the largest diameter of the skull. In molded (reshaped) fetal heads, the leading bony part of the skull may be below the ischial spines while the largest diameter of the fetal skull still remains above the pelvic inlet. An attempt at assisted vaginal birth in such a situation would be associated with risks. Therefore, the vaginal or transperineal assessments of station should be supplemented with a transabdominal examination. We suggest a method for the assessment of fetal head descent with transabdominal ultrasound. To investigate the correlation between transabdominal and transperineal assessment of fetal head descent, and to study fetal head shape at different labor stages and head positions. Women with term singleton cephalic pregnancies admitted to the labor ward for induction of labor or in spontaneous labor, at the Cairo University Hospital and Oslo University Hospital from December 2019 to December 2020 were included. Fetal head descent was assessed with transabdominal ultrasound as the suprapubic descent angle between a longitudinal line through the symphysis pubis and a line from the upper part of the symphysis pubis extending tangentially to the fetal skull. We compared measurements with transperineally assessed angle of progression and investigated interobserver agreement. We also measured the part of fetal head above and below the symphysis pubis at different labor stages. The study population comprised 123 women, of whom 19 (15%) were examined before induction of labor, 8 (7%) in the latent phase, 52 (42%) in the active first stage and 44 (36%) in the second stage. The suprapubic descent angle and the angle of progression could be measured in all cases. The correlation between the transabdominal and transperineal measurements was -0.90 (95% confidence interval, -0.86 to -0.93). Interobserver agreement was examined in 30 women and the intraclass correlation coefficient was 0.98 (95% confidence interval, 0.95-0.99). The limits of agreement were from -9.5 to 7.8 degrees. The fetal head was more elongated in occiput posterior position than in non-occiput posterior positions in the second stage of labor. We present a novel method of examining fetal head descent by assessing the proximal part of the fetal skull with transabdominal ultrasound. The correlation with transperineal ultrasound measurements was strong, especially early in labor. The fetal head was elongated in the occiput posterior position during the second stage of labor.

Kamel R ，Negm S ，Badr I ，Kahrs BH ，Eggebø TM ，Iversen JK ... -  《-》

Fetal descent in nulliparous women assessed by ultrasound: a longitudinal study.

Ultrasound measurements offer objective and reproducible methods to measure the fetal head station. Before these methods can be applied to assess labor progression, the fetal head descent needs to be evaluated longitudinally in well-defined populations and compared with the existing data derived from clinical examinations. This study aimed to use ultrasound measurements to describe the fetal head descent longitudinally as labor progressed through the active phase in nulliparous women with spontaneous onset of labor. This was a single center, prospective cohort study at the Landspitali - The National University Hospital of Iceland, Reykjavik, Iceland, from January 2016 to April 2018. Nulliparous women with a single fetus in cephalic presentation and spontaneous labor onset at a gestational age of ≥37 weeks, were eligible. Participant inclusion occurred during admission for women with an established active phase of labor or at the start of the active phase for women admitted during the latent phase. The active phase was defined as an effaced cervix dilated to at least 4 cm in women with regular contractions. According to the clinical protocol, vaginal examinations were done at entry and subsequently throughout labor, paired each time with a transperineal ultrasound examination by a separate examiner, with both examiners being blinded to the other's results. The measurements used to assess the fetal head station were the head-perineum distance and angle of progression. Cervical dilatation was examined clinically. The study population comprised 99 women. The labor patterns for the head-perineum distance, angle of progression, and cervical dilatation differentiated the participants into 75 with spontaneous deliveries, 16 with instrumental vaginal deliveries, and 8 cesarean deliveries. At the inclusion stage, the cervix was dilated 4 cm in 26 of the women, 5 cm in 30 of the women, and ≥6 cm in 43 women. One cesarean and 1 ventouse delivery were performed for fetal distress, whereas the remaining cesarean deliveries were conducted because of a failure to progress. The total number of examinations conducted throughout the study was 345, with an average of 3.6 per woman. The ultrasound-measured fetal head station both at the first and last examination were associated with the delivery mode and remaining time of labor. In spontaneous deliveries, rapid head descent started around 4 hours before birth, the descent being more gradual in instrumental deliveries and absent in cesarean deliveries. A head-perineum distance of 30 mm and angle of progression of 125° separately predicted delivery within 3.0 hours (95% confidence interval, 2.5-3.8 hours and 2.4-3.7 hours, respectively) in women delivering vaginally. Although the head-perineum distance and angle of progression are independent methods, both methods gave similar mirror image patterns. The fetal head station at the first examination was highest for the fetuses in occiput posterior position, but the pattern of rapid descent was similar for all initial positions in spontaneously delivering women. Oxytocin augmentation was used in 41% of women; in these labors a slower descent was noted. Descent was only slightly slower in the 62% of women who received epidural analgesia. A nonlinear relationship was observed between the fetal head station and dilatation. We have established the ultrasound-measured descent patterns for nulliparous women in spontaneous labor. The patterns resemble previously published patterns based on clinical vaginal examinations. The ultrasound-measured fetal head station was associated with the delivery mode and remaining time of labor.

Hjartardóttir H ，Lund SH ，Benediktsdóttir S ，Geirsson RT ，Eggebø TM ... -  《-》

Transperineal ultrasound imaging in prolonged second stage of labor with occipitoanterior presenting fetuses: how well does the 'angle of progression' predict the mode of delivery?

To compare the angle of progression on transperineal ultrasound imaging between different modes of delivery in prolonged second stage of labor with occipitoanterior fetal position. We prospectively evaluated 41 women at term (>or= 37 weeks) with failure to progress in the second stage of labor. Only cases with occipitoanterior fetal position were included in the final analysis. These cases were classified into three groups: Cesarean section for failure to progress, vacuum extraction for failure to progress, and spontaneous delivery following prolonged second stage of labor. Transperineal ultrasound examination was performed just before digital examination and subsequent delivery. The angle between a line placed through the midline of the pubic symphysis and a line running from the inferior apex of the symphysis tangentially to the fetal skull (the so-called 'angle of progression') was measured offline by an observer blinded to the mode of delivery. There were 26 cases with occipitoanterior fetal position (Cesarean section, n = 5; vacuum extraction, n = 16; spontaneous delivery, n = 5). Logistic regression analysis showed a strong relationship between the angle of progression and the need for Cesarean delivery (R(2) measure of fit = 55%, likelihood ratio chi-square P < 0.0001). When the angle of progression was 120 degrees , the fitted probability of either an easy and successful vacuum extraction or spontaneous vaginal delivery was 90%. This is the first report to document a strong relationship between an objective ultrasound marker (angle of progression) and the mode of delivery following prolonged second stage of labor with occipitoanterior fetal position. A predictive model using this parameter would allow better decision making regarding operative delivery for obstructed labor.

Kalache KD ，Dückelmann AM ，Michaelis SA ，Lange J ，Cichon G ，Dudenhausen JW ... -  《-》