Correlation between clinical fetal head station and sonographic angle of progression during the second stage of labor

Purpose: To investigate the correlation between the angle of progression and the clinical fetal head station (FHS) during the second stage of labor, and to build reference range.

Materials and methods: A prospective, observational study was conducted. Women carrying singleton term pregnancies were enrolled during the second stage of labor. FHS was assessed manually by a senior obstetrician, while the angle of progression (AOP) was assessed by transperineal ultrasound (TPU). Both examiners were blinded to each others results. The correlation between the sonographic AOP and the clinical FHS was analyzed.

Results: Seventy patients comprised the study group. Clinical FHS demonstrated an excellent correlation with the sonographic measurement of AOP (Pearson’s Correlation 0.642, p?2?=?0.423, p?Conclusions: Our results demonstrate a significant correlation between the clinical FHS and the TPU measured AOP. These standardized sonographic values may serve the obstetrician as a reliable, objective auxiliary tool for the evaluation of the FHS during the second stage of labor.     

Automated 3D ultrasound measurement of the angle of progression in labor

Objectives: To assess the feasibility and reliability of an automated technique for the assessment of the angle of progression (AoP) in labor by using three-dimensional (3D) ultrasound.

Methods: AoP was assessed by using 3D transperineal ultrasound by two operators in 52 women in active labor to evaluate intra- and interobserver reproducibility. Furthermore, intermethod agreement between automated and manual techniques on 3D images, and between automated technique on 3D vs 2D images were evaluated.

Results: Automated measurements were feasible in all cases. Automated measurements were considered acceptable in 141 (90.4%) out of the 156 on the first assessments and in all 156 after repeating measurements for unacceptable evaluations. The automated technique on 3D images demonstrated good intra- and interobserver reproducibility. The 3D-automated technique showed a very good agreement with the 3D manual technique. Notably, AoP calculated with the 3D automated technique were significantly wider in comparison with those measured manually on 3D images (133?±?17° vs 118?±?21°, p?=?0.013).

Conclusions: The assessment of the angle of progression through 3D ultrasound is highly reproducible. However, automated software leads to a systematic overestimation of AoP in comparison with the standard manual technique thus hindering its use in clinical practice in its present form.     

Role of ultrasound in the labor ward

Intrapartum ultrasound is commonly used to evaluate fetal vitality, presentation and status as well as placental location. Health professionals are increasingly using intrapartum ultrasound for advanced applications that have not yet been shown to be effective by controlled research studies, using advanced ultrasound technologies such as bi-dimensional ultrasound, color ultrasound, pulsed Doppler ultrasound and three-dimensional ultrasound. This article reviews the current applications of intrapartum ultrasound and considers which advanced technologies can add to the standard of care in the delivery ward.     

Intrapartum transperineal ultrasound as a predictor of instrumentation difficulty with vacuum-assisted delivery in primiparous women

Objectives: To assess the capability of different intrapartum transperineal ultrasound parameters to predict the difficulty of vacuum extraction. This is a prospective observational study performed between 04/2012 and 03/2013 on 72 primiparous-women, ≥37-weeks with singleton pregnancies at full dilatation that underwent transperineal ultrasound before vacuum placement for foetal extraction. Working in a transperineal longitudinal plane we evaluated: progression-angle, progression-distance and head direction; in a transverse plane: midline-angle and head-perineum distance. The vacuum extractions were classified as easy-group (EG) (≤3 vacuum pulls), difficult/impossible-group (DG)(≥4 pulls). Occiput-posterior presentations were not assessed.

Results: Fifty-two (52) patients were studied (26 patients per study group). No differences were observed in obstetric, neonatal or intrapartum characteristics between the study groups, with the following exceptions: new-born (NB) weight (3147?g versus 3540?g) and the number of vacuum pulls (1.4 EG versus 4.3 DG; p?<?0.0005). The progression angle was 133.1° (123°–143°) in EG and 109.2° (97.2°–121.2°) in DG (p?<?0.0005); up direction of foetal head was 88% versus 34.5% (p?<?0.0005); progression distance was 37?mm (26.6–47.4) versus 29.9?mm (8.8–51; p?=?0.003); midline angle was 35° (15.4°–54.6°) versus 59.7° (34.5°–84.9°; p?=?0.0005); head-perineum distance was 41.9?mm (35.2–48.6) versus 48.9?mm (40.5–57.3; p?=?0.017). The area under the Receiver Operating Characteristic (ROC) curve for the progression angle was 0.9 (95%CI, 0.82–0.99), and the midline angle was 0.8 (95%CI, 0.67–0.92).

Conclusion: If previous to the placement of the vacuum cup the progression angle is ≤120°, the foetal head direction is horizontal or down, and the midline angle is ≥35°, there is an 85% chance that the delivery will require more than 4 vacuum pulls.     

Relationship between intrapartum transperineal ultrasound measurement of angle of progression and head–perineum distance with correlation to conventional clinical parameters of labor progress and time to delivery

Objective: To assess whether angle of progression (AOP) and head–perineum distance (HPD) measured by intrapartum transperineal ultrasound (ITU) correlate with clinical fetal head station (station); and whether AOP versus HPD varies during uterine contraction and relaxation. In a subset of primipaorus women, whether these ITU parameters correlate with time to normal spontaneous delivery (TD).

Methods: We evaluated prospectively 100 primiparous and multiparous women at term in active labor. Transabdominal and transperineal ultrasound (sagittal and transverse plane) were used to measure fetal head position and ITU parameters, respectively. Digitally palpated station and cervical dilatation were also noted. The results were compared using regression and correlation coefficients.

Results: Station was moderately correlated with AOP (r?=?0.579) and HPD (r?=??0.497). AOP was highly correlated with HPD during uterine contraction (r?=??0.703) and relaxation (r?=??0.647). In the subgroup of primiparous women, natural log of TD has the highest correlation with HPD and AOP during uterine contraction (r?=?0.742), making prediction of TD similar to that of using cervical dilatation.

Conclusion: ITU parameters were moderately correlated with station. There was constant high correlation between AOP and HPD. Prediction of TD in primiparous women using ITU parameters was similar to that of using cervical dilatation.     

A longitudinal study investigating cervical changes during labor using a wireless ultrasound device

Purpose: Cervical assessment during digital vaginal examination (DVE) includes assessing cervical dilatation, effacement, position and consistency. Only cervical dilatation during labor has been previously researched. We investigated cervical changes, including cervical dilatation and effacement, using a wireless ultrasound (US) device.

Materials and methods: This was a longitudinal study investigating cervical changes during labor using a wireless US device. Twenty-five women in labor participated in a serial comparison of cervical dilatation, length and thickness measured during intrapartum transperineal sonography using a wireless mobile US device (SONON) with measurements of cervical dilatation and effacement obtained during serial DVEs.

Results: Intrapartum sonography showed strong correlation with DVE in assessing cervical changes during labor including the measurement of cervical dilatation and thickness (p?Conclusions: We developed a new technique for evaluating effacement with cervical thickness. Cervical dilation and thickness using a transperineal intrapartum US demonstrated significant correlation with DVE findings. The use of a wireless US device is convenient and may be advantageous in the labor ward; however, further research is needed to define the role of this wireless device.     

Utility of intrapartum transperineal ultrasound to predict cases of failure in vacuum extraction attempt and need of cesarean section to complete delivery

Objectives: We aim to evaluate the predictive capacity of intrapartum transperineal ultrasound (ITU) to predict cases of failure in fetal extraction in operative deliveries with vacuum. Prospective, observational study performed on 61 nulliparous women, ≥37 weeks, singleton pregnancies at full dilatation who underwent transperineal ultrasound before placement of vacuum to complete fetal extraction. Working on the transperineal longitudinal plane, we evaluated the following: Angle of Progression (AoP), Progression Distance (PD) and head direction. In the transverse plane, midline angle (MLA) and head–perineum distance were assessed. Vacuum extractions were classified as easy (EG) (three or less vacuum pulls), difficult (DG) (more than three vacuum pulls) or impossible (IG) (delivery completed by cesarean section). Occipito-posterior presentations were not evaluated.

Results: Fifty-two patients were studied (26-EG, 19-DG and 7-IG). No differences in obstetric, intrapartum or neonatal characteristics were observed between study groups, with the following exceptions: weight at birth (3147?g-EG, 3523?g-DG and 3588?g-IG) and number of vacuum pulls (1.4-EG, 4.4-DG and 4.1-IG; p?<?0.0005). The AoP pushing was 133.1°?±?13.6-EG, 112.8°?±?12.8-DG and 99.1°?±?8.9-IG (p?<?0.0005); “head-up” direction was identified in 84.6% of EG, 36.8% of DG and 28.6% of IG (p?<?0.001); PD were 37.0?±?10.4?mm, 33.3?±?23.3?mm and 20.8?±?9.5?mm (p?<?0.0005); MLA were 35.0°?±?19.6, 55.3°?±?24.4 and 76.0°?±?23.2 (p?=?0.003); and head–perineum distances were 41.8?±?6.6?mm, 49.2?±?9.8?mm and 48.0?±?3.4?mm (p?=?0.072), respectively.

Conclusion: We have observed that the presence of an AoP with pushing <105°, a PD <25?mm, a “head-down” direction and a >45° MLA are very unfavorable ITU parameters which can be used to identify cases of high risk of fetal extraction failure in vacuum-assisted deliveries.     

Levels of agreement between clinical examination and transabdominal ultrasound evaluation of fetal head position in the second stage of labor

Aim: To compare transvaginal digital examination performed by residents and attending physicians to transabdominal suprapubic ultrasound in the evaluation of fetal head position in the second stage of labor.

Methods: A prospective study was conducted at a tertiary center and included pregnant women at term, with normal singleton cephalic presentation fetuses. All patients had ruptured membranes and were evaluated during the second stage of labor. Fetal head position was assessed consecutively by two clinicians (one resident and one attending physician). Afterwards, transabdominal suprapubic ultrasound was performed by another observer. Examiners were blinded to each other’s findings. Cohen’s kappa test was used to assess the degree of agreement between the evaluation methods.

Results: One-hundred sixty-one women were included. Transvaginal examination was consistent with the ultrasound in 45.0% of cases (95% CI: 37–53%) when the examination was performed by residents (k?=?0.349) and in 67% (95% CI: 60–74%) if the attending physician carried out the evaluation (k?=?0.604). When considering only the anterior positions, the Cohen’s kappa test was 0.426 and 0.709, respectively.

Conclusion: Transabdominal suprapubic ultrasound improved the accuracy of the evaluation of fetal head position, namely when transvaginal digital examination was performed by residents. This may be important especially when instrumental deliveries are considered.     

Prediction of outcome in twin pregnancy with first and early second trimester ultrasound

Abstract

Objective: To establish if first or second trimester biometry is a useful adjunct in the prediction of adverse perinatal outcome in twin pregnancy.

Methods: A consecutive cohort of 1028 twin pregnancies was enrolled for the Evaluation of Sonographic Predictors of Restricted growth in Twins (ESPRiT) study, a prospective study conducted at eight academic centers. Outcome data was recorded for 1001 twin pairs that completed the study. Ultrasound biometry was available for 960 pregnancies. Biometric data obtained between 11 and 22 weeks were evaluated as predictors of a composite of adverse perinatal outcome (mortality, hypoxic ischemic encephalopathy, periventricular leukomalacia, necrotizing enterocolitis, respiratory distress, or sepsis), preterm delivery (PTD) and birthweight discordance greater than 18% (18% BW). Outcomes were adjusted for chorionicity and gestational age using Cox Proportional Hazards regression.

Results: Differences in crown-rump length (CRL) were not predictive of adverse perinatal outcome. Between 14 and 22 weeks, a difference in abdominal circumference (AC) of more than 10% was the most useful predictor of adverse outcome, PTD and 18% or more BW discordance in all twins. Overall the strongest correlation was observed for intertwin differences in biometry between 18 and 22 weeks.

Conclusion: Biometry in the early second trimester can successfully identify twin pregnancies at increased risk. Intertwin AC difference of greater than 10% between 14 and 22 weeks gestation was the best individual predictor of perinatal risk in all twins. Sonographic biometry in the early second trimester should therefore be utilized to establish perinatal risk, thus allowing prenatal care to be improved.     

Changes in levator hiatus dimensions during pregnancy and after delivery in nulliparas: a prospective cohort study using 3D transperineal ultrasound

Purpose: The purpose of this study was to investigate the changes that occur in the levator ani muscle (1) during pregnancy and (2) after labor depending on the mode of delivery in a cohort of nulliparas.

Materials and methods: A prospective cohort longitudinal study, consisting of 84 primiparas who were examined and recruited in an antenatal clinic was conducted. All participants were submitted to a real-time three-dimensional (3D) ultrasonographic evaluation of the levator ani at (1) 12, (2) 22, and (3) 32 weeks of pregnancy (4) and 4–6 months postdelivery. The 3D volumes were acquired and stored for an offline analysis.

Results: Data from 59 women with at least two measurements were available for analysis. 35 women were delivered vaginally and 24 via cesarean section. There was a statistical increase in the dimensions of the levator hiatus at each pregnancy trimester when compared to the measurements of the previous trimesters. After vaginal delivery, hiatal dimensions increased compared to the third-trimester measurements; after cesarean section, hiatal dimensions decreased.

Conclusions: This study supports that in primiparas, the dimensions of the levator hiatus increase significantly during pregnancy and subsequently either increase further after vaginal delivery or decrease to the first-trimester levels after cesarean section.     

Preterm premature rupture of membrane assessment via transperineal ultrasonography: a diagnostic accuracy study

Objective: The objective of this study is to evaluate diagnostic accuracy of transperineal ultrasound assessment compared to speculum examination by using placental alfa-microglobulin (PAMG)-1 tests as reference.

Methods: This was a prospective observational study conducted in Ankara University Hospital. Women with early and late preterm pregnancies with suspected rupture of membranes, i.e. women with a complaint of fluid leakage (105 in total) were enrolled. Prior to speculum examination, sagittal and transverse plane views of the fornices and cervix were obtained via transperineal ultrasonography and images were stored. Then the speculum examination for amniotic fluid pooling was performed. Definite diagnoses were made with PAGM-1 assays. After collection of the data, ultrasound images were analyzed by an observer blind to physical examination findings. Hypoechogenic fluid appearance around the cervix and in the fornices was considered positive for preterm premature rupture of membranes (PPROM). Results of physical and ultrasound examination were compared with PAMG-1 test as a reference method. The diagnostic performance of transperineal ultrasound was tested with accuracy parameters and receiver-operating characteristics (ROC) curves. Inter-rater reliability was analyzed with Cohen’s kappa.

Results: In total, 103 pregnant women were evaluated. The prevalence of PPROM in our study population was 43.14%. At a 5?mm diagnostic threshold, the sensitivity and specificity values of transperineal assessment were 95.45% (95% CI: 84.50–99.31%) and 96.55% (95% CI: 88.07–99.48%), respectively, and they were comparable with speculum examination in a population of preterm pregnant women with suspected PPROM (p?>?0.05). Interobserver reliability analysis with Cohen’s kappa has shown good very good agreement with the kappa value of 0.93 (95% CI 0.87–1.00).

Conclusions: Transperineal ultrasonography is a novel method that can be used to assess vaginal pooling of amniotic fluid. Ultrasonography offers similar sensitivity and specificity compared with speculum examination and it is non-invasive.     

The feasibility and accuracy of ultrasound assessment in the labor room

Objective: Vaginal examination is widely used to assess the progress of labor; however, it is subjective and poorly reproducible. We aim to assess the feasibility and accuracy of transabdominal and transperineal ultrasound compared to vaginal examination in the assessment of labor and its progress.

Methods: Women were recruited as they presented for assessment of labor to a tertiary inner city maternity service. Paired vaginal and ultrasound assessments were performed in 192 women at 24–42 weeks. Fetal head position was assessed by transabdominal ultrasound defined in relation to the occiput position transformed to a 12-hour clock face; fetal head station defined as head-perineum distance by transperineal ultrasound; cervical dilatation by anterior to posterior cervical rim measurement and caput succedaneum by skin-skull distance on transperineal ultrasound.

Results: Fetal head position was recorded in 99.7% (298/299) of US and 51.5% (154/299) on vaginal examination (p?¹). Bland–Altman analysis showed 95% limits of agreement, ?5.31 to 4.84 clock hours. Head station was recorded in 96.3% (308/320) on vaginal examination (VE) and 95.9% (307/320) on US (p?=?.79¹). Head station and head perineum distance were negatively correlated (Spearman’s r?=??.57, p?p?p?p?Conclusions: We describe comprehensive ultrasound assessments in the labor room that could be translated to the assessment of women in labor. Fetal head position is unreliably determined by vaginal examination and agrees poorly with US. Head perineum distance has a moderate correlation with fetal head station in relation to the ischial spines based on vaginal examination. Cervical dilatation is not reliably assessed by ultrasound except at dilatations of less than 4?cm. Caput is readily quantifiable by ultrasound and its presence is associated with lower fetal head station. Transabdominal and transperineal ultrasound is feasible in the labor room with an accuracy that is generally greater than vaginal examinations.     

Impact of intrapartal ultrasound to assess fetal head position and station on the type of obstetrical interventions at full cervical dilatation

Objectives: Recent ultrasound studies have shown that it is feasible to objectively and reproducibly assess fetal head position and station within the pelvis. We sought to evaluate the impact of this new approach on decision making by physicians in a cohort of women with a prolonged second stage of labor. Methods: This was a retrospective cohort study that included all women with fetuses in cephalic presentation, who were diagnosed with a prolonged second stage of labor, and who delivered in a 1-year period. We compared a group of women (n?=?121) with a prolonged second stage of labor who underwent intrapartal ultrasound prior to obstetrical intervention (Group A, n?=?43) with a group of women for whom the delivery modus was decided upon after clinical digital examination alone (Group B, n?=?78). Results: There were no significant differences in maternal and neonatal morbidity between both groups. The rate of second-stage cesarean section was significantly higher (p?<?0.50) in Group B without ultrasound compared to Group A with ultrasound prior to operative delivery (20/78 vs. 7/43). Seven patients in Group A delivered spontaneously, but none of the patients in Group B had spontaneous deliveries. Conclusions: Intrapartal ultrasound in patients with a prolonged second stage of labor may change obstetrical practice by reducing the number of second stage cesarean section without increasing maternal and neonatal morbidity.     

Intrapartum translabial ultrasound with pushing used to predict the difficulty in vacuum-assisted delivery of fetuses in non-occiput posterior position

Objective: Our aim is to evaluate the capacity of intrapartum translabial ultrasound (ITU) with pushing in the prediction of difficulty of fetal extraction in vacuum assisted deliveries. Prospective, observational study performed (2/2015–8/2015) on 75 nulliparous women, ≥37 weeks with singleton pregnancies at full dilatation who had ITU-with-pushing performed, previous to vacuum-placement for fetal extraction. Working on the translabial sagittal-plane, we assessed: Angle-Progression (AoP), Progression-Distance (PD) and Head-Direction (HD); in the axial plane we evaluated: Midline-Angle (MLA) and Head-Perineum-Distance (HPD). Vacuum extractions were classified as easy-difficulty (ED) (≤3 vacuum-pulls), difficult-unsuccessful (DD) (>3 vacuum-pulls). We did not assess occipito-posterior-presentations.

Results: Seventy nulliparous were studied (44-ED,26-DD). We observed no differences in obstetric, neonatal or intrapartum characteristics between the two study groups, with the following exceptions: newborn weight (3272?±?438?g versus 3540?±?372?g; p?=?0.011) and number of vacuum-pulls (1.4-ED-vs-4.4-DD; p?<?0.0005). AoP-pushing was 143.9°?±?14.6° in ED and 115.1°±?12.9° in DD (p?<?0.0005); Head-Up was 79.5% versus 38.4% (p?<?0.0005); PD-Pushing was 42.7?±?11.3?mm versus 30.4?±?9.8?mm (p?<?0.0005); MLA-Pushing was 27.6°±?26.6° versus 57.5°±26.5°(p=0.025); HPD-Pushing was 40.8?±?10.0?mm versus 47.4?±?10.9?mm (p?=?0.039).

Conclusion: We identified that the presence of an AoP-Pushing?>?128° predicts an Easy-Vacuum-Delivery (≤3 Vacuum-Pulls) in >85% of cases (Sen 80%–FPR 9.3%).     

Correlation between umbilical arterial pH values and fetal vertebral artery Doppler waveforms at the beginning of the second stage of labor: a pilot prospective study

Objective: The aim of this study was to evaluate the association between umbilical arterial pH and fetal vertebral artery Doppler velocimetry waveforms measured at the beginning of the second stage of labor in physiological term pregnancies.

Methods: This was a prospective cohort study of 250 pregnancies. The resistance index, pulsatility index, and peak systolic velocity were measured. The relationship between the fetal Doppler and the umbilical arterial pH was evaluated. A simple linear regression and a general linear model were used to explore possible correlations of Doppler parameters with fetal and neonatal outcome adjusted for confundents.

Results: Umbilical arterial pH values were directly associated with vertebral artery pulsatility index. Fetuses with lower pulsatility index values were at increased risk of a subsequent diagnosis of pathological fetal heart rate tracing patterns (presence of decelerations or reduced variability according to FIGO criteria during the second stage of labor). We estimated a decrease in pulsatility index of 10% in those fetuses destined to show a pathological fetal heart rate tracing.

Conclusion: Vertebral artery Doppler waveforms correlates with umbilical pH in normal pregnancies and is also a function of fetal heart rate patterns. If this proportional association would be demonstrated also for abnormal pH values, vertebral artery pulsatility index might be useful to evaluate fetal wellbeing in those cases of suspected hypoxia/academia.