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

Depósito de investigación de la Universidad de Sevilla https://idus.us.es/ Esta es la versión aceptada del artículo publicado en: This is a accepted manuscript of a paper published in: The Journal of Maternal-Fetal & Neonatal Medicine (2016) DOI: 10.3109/14767058.2015.1130816 Copyright: El acceso a la versión publicada del artículo puede requerir la suscripción de la revista. Access to the published version may require subscription. “This is an Accepted Manuscript of an article published by Taylor & Francis in [The Journal of Maternal-Fetal & Neonatal Medicine] on [2016], available at: https://doi.org/[10.3109/14767058.2015.1130816].” The Journal of Maternal-Fetal & Neonatal Medicine Intrapartum translabial ultrasound with pushing used to predict the difficulty in vacuum-assisted delivery of fetuses in non-occiput posterior position José Antonio Sainz, Carlota Borrero, Adriana Aquise, José Antonio García- Mejido, Laura Gutierrez & Ana Fernández-Palacín To cite this article: José Antonio Sainz, Carlota Borrero, Adriana Aquise, José Antonio García- Mejido, Laura Gutierrez & Ana Fernández-Palacín (2016) Intrapartum translabial ultrasound with pushing used to predict the difficulty in vacuum-assisted delivery of fetuses in nonocciput posterior position, The Journal of Maternal-Fetal & Neonatal Medicine, 29:20, 3400-3405, DOI: 10.3109/14767058.2015.1130816 ORIGINAL ARTICLE Intrapartum translabial ultrasound with pushing used to predict the difficulty in vacuum-assisted delivery of fetuses in non-occiput posterior position Jose´ Antonio Sainz1,2, Carlota Borrero1, Adriana Aquise1, Jose´ Antonio Garc´ıa-Mejido1, Laura Gutierrez1, and Ana Ferna´ndez-Palac´ın3 1 Department of Obstetrics and Gynecology, Valme University Hospital, Seville, Spain, 2 Department of Obstetrics and Gynecology, University of Seville, Spain, and 3 Biostatistics Unit, Department of Preventive Medicine and Public Health, University of Seville, Spain Keywords Intrapartum ultrasound, labor, pushing, transperineal ultrasound, vacuum delivery Abstract 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) (43 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 ¼ 0.011) and number of vacuum-pulls (1.4-ED-vs-4.4-DD; p50.0005). AoP-pushing was 143.9◦ ± 14.6◦ in ED and 115.1 ◦ ± 12.9 ◦ in DD (p 5 0.0005); Head-Up was 79.5% versus 38.4% (p 5 0.0005); PD-Pushing was 42.7 ± 11.3 mm versus 30.4 ± 9.8 mm (p50.0005); MLA-Pushing was 27.6◦± 26.6◦ versus 57.5◦±26.5◦(p¼0.025); HPD-Pushing was 40.8 ± 10.0 mm versus 47.4 ± 10.9 mm (p ¼ 0.039). Conclusion: We identified that the presence of an AoP-Pushing4128◦ predicts an Easy-Vacuum- Delivery (≤3 Vacuum-Pulls) in 485% of cases (Sen 80%–FPR 9.3%). Introduction Digital examination is subjective and unreliable in the evaluation of the degree of engagement and position of the fetal head during labor [1]. Intrapartum translabial ultrasound (ITU) has proved to be an objective tool to predict the type of delivery that will take place when used in second stage of labor. ITU has also begun to be used with the aim of predicting the difficulty of instrumentation in fetal extraction, since instrumental deliveries are associated with an increase in maternal and neonatal morbidity [2–9]. Achieving a successful instrumentation will result in a reduction of this increased morbidity (subdural or cerebral hemorrhage, convulsions, mechanical ventilation) [10–12]. Our group [13] assessed the capacity of ITU in the prediction of difficulty of fetal extraction in vacuum assisted deliveries. If previous to vacuum placement, an angle of progression ≤120◦, a horizontal or downwards head direction, and a midline angle ≥35◦ was identified, the probability of a ‘‘difficult’’ delivery, thus more than 3 pulls needed to achieve fetal extraction, is of 85% [13]. Now, we aim to evaluate this ITU’s predictive capacity for instrumentation difficulty with vacuum, in the expulsion stage with pushing (angle of progression, progression distance, head direction, midline angle and head perineum distance). Material and method Prospective, observational study was carried out between February 2015 and August 2015, at Valme’s Universisty Hospital in Seville, on 75 pregnant women at term, admitted to our delivery unit during second stage of labor, and who required instrumentation to complete fetal extraction. Throughout these 7 months (February–August 2015) at Valme’s Hospital we have had a total of 2625 deliveries, with a twin rate of 1.8% (47 cases), a cesarean section rate of 20.1% (527 cases) and a 15.1% of instrumental deliveries (398 cases, 320 vacuum-assisted deliveries (80.4%) and 78 forceps-assisted deliveries (19.5%)). All 75 patients shared the following characteristics: low risk, at term singleton pregnancy (37–42), in nulliparous, during active second stage of labor, with ruptured membranes and fetus in cephalic presentation and including both spontaneous and induced initiation of labor cases. Pregnancies involving serious maternal or fetal pathology were excluded from the study. A vacuum was used for fetal extraction, although delivery could have been completed either vaginally or abdominally (cesarean section). Prior to instrumental delivery, once in active second stage of labor, ruptured membranes and full dilatation, ITU was used to perform an evaluation of fetal head position [14]. The ITU was performed with the pregnant woman in lithotomy position and under empty bladder conditions. Capture was obtained by placing the transducer with a translabial insonation at a transperineal level. Since the pubic symphisis would be used as the reference longitudinal axis, we ensured its whole length was included in the capture. Angle of progression (AoP) was used as the angle between the longitudinal axis of the pubic symphysis and the tangent line to fetal skull’s contour [15]. Pubis middle line can be identified by the presence of the fibrocartilaginous disk and capsule [16] (Figure 1); progression distance (PD) – as the distance (mm) between the infrapubic symphisis and the lowest edge of fetal skull [17] (Figure 2); and Head Direction (HD) – as the angle resulting from the union of a perpendicular line to pubic’s bone major axis and a perpendicular line to fetal’s head widest transverse diameter; angles ≥30◦ correspond to ‘‘upward’’ directions, ≤0◦ correspond to ‘‘downward’’ directions, and angles between 0◦ and 30◦ correspond to horizontal directions [18]; were the sonographic parameters evaluated, which were measured both in rest and with pushing during maternal contraction. We then turned our transducer to switch from the midsagittal to an axial plane, allowing us to identify fetal’s brain midline. We used this view to evaluate the midline angle (MLA; defined as the angle between the anteroposterior axis of the pelvis and the fetal’s brain midline) [19], both at rest and with pushing. To assess these parameters, we used a Toshiba Famio 8 (Tokyo, Japan) ultrasound machine with a 3.75 MHz convex probe. Intrapartum ultrasound evaluation was carried out by two senior obstetricians, with more than 5 years of experience in obstetric ultrasonography. Once this intrapartum ultrasound assessment was completed, fetal extraction was performed by other two senior obstetricians, with more than 15 years of experience in operative deliveries. In all cases, a metal vacuum (Bird’s cup 50 mm, 80 KPa) was used to finalize vaginal delivery, without taking into account the previously recorded ultrasound data obstetricians performing fetal extraction had no information about ITU results previously recorded. In all cases, a metal vacuum (Bird’s cup 50 mm, 80 KPa) was used to finalize vaginal delivery, without taking into account the previously recorded ultrasound data as obstetricians performing fetal extraction had no information about ITU results previously recorded. Placement of the suction cup over the flexion point was considered avoiding caput succedaneum and rapid negative pressure (over 2 minutes) application of the vacuum (until 0.6–0.8 kg/cm2). Vacuum traction is performed in the moment of contraction along with maternal push, at a rate of 2–3 vacuum tractions per contraction and without associating Kristeller maneuver [20,21]. The procedure was abandoned after 3 cup slides or 15 minutes without achieving fetal extraction [22]. According to the number of vacuum pulls needed to complete the delivery, instrumentation was classified as ‘‘easy’’ (3 or less pulls), difficult (more 3 pulls) or impossible (vaginal fetal extraction was not achieved and a cesarean section had to be performed) [18,23]. All cases of occipitoposterior position were excluded from our evaluation. The study was approved by local ethics and research committees, and all participants were previously asked to sign an informed consent. After delivery, both maternal and neonatal morbidity and mortality data were collected. Presence of perineal tears, uterine atony, bleeding degree and need for postpartum surgery were the maternal parameters recorded. New born data registered were: fetal weight, Apgar test result (at 1 and 5 min), fetal pH at birth, presence of neonatal morbidity (cephalohaematoma, brachial plexus palsy, etc.), admission to neonatalogy and neonatal mortality. Statistical analysis was performed using IBM SPSS Statistics software version 22 (Armonk, NY). We determined means and standard deviation for numeric variables, and percentages for qualitative variables. Comparisons of numeric variables between instrumentation difficulty groups (easy, difficult and impossible) were carried out using Student’s t-test. The comparisons of the qualitative variables between the groups were carried out using the Chisquare test. We determined areas under the ROC curves for the ultrasound variables studied and their 95% confidence intervals, and we identified the cutoff points that predicted an at least 85% chance of easy delivery. Figure 1. (A) Angle of Progression at rest. (B) Angle of Progression with pushing. Figure 2. (A) Progression distance at rest. (B) Progression distance with pushing. Results We analyzed 75 pregnant women in labor without previous history of vaginal delivery. 5 cases were excluded from the analysis: 2 due to occipito posterior fetal position identified in the intrapartum ultrasound evaluation, 2 due to fetal extraction using a different instrument other than vacuum extractor and 1 case because of incomplete ultrasound data collection. Table 1 displays both maternal and labor characteristics, and neonatal results of our study population (70 pregnant women), divided according to instrumentation difficulty (easy, difficult-impossible instrumentation). All patients had epidural analgesia administered and fetal extraction was completed by vacuum-assisted delivery. Two new-borns were admitted to Neonatology unit: the first one due to jaundice, receiving 48 h of light therapy, while the second one presented mild respiratory distress, and was discharged in the first 24 h. Five cases of failed vacuum-assisted delivery are included in the ‘‘difficult-impossible instrumentation’’ group, requiring c-section to complete fetal extraction. Average maternal age for this group was 29.1 ± 6.5 years, with a mean gestational age of 39.2 ± 1.5 weeks, 4.6 ± 1.4 vacuum pulls and a mean birth weight of 3620 ± 390 grams. No cases of neonatal morbidity were registered in this group. Intrapartum ultrasound parameters are displayed in Table 2, describing general and individual study group (easy and difficult-impossible instrumentation) results. In Figures 3 and 4, we display the ROC curves of the angle of progression and progression distance with pushing, in order to predict the difficulty of vaginal delivery with vacuum. The parameters used in predicting the difficulty of operative delivery with vacuum using ITU, both at rest and with pushing, were: angle of progression 120.5◦ and 128◦, progression distance 35.5 mm and 37.5 mm and midline angle 43◦ and 28◦ respectively (Table 3). Table 1. Maternal and neonatal characteristics in 70 pregnancies requiring vacuum delivery. Easy vacuum Difficult-Impossible vacuum delivery Total (n ¼ 70) delivery (n ¼ 44) (n ¼ 26) p Maternal age (years) 29.7 ± 5.9 29.7 ± 6.6 29.6 ± 5.0 0.9 Maternal BMI (kg/m2) 25.07 ± 5.0 25.03 ± 4.4 25.35 ± 8.0 0.8 Maternal smoking (≥1 cigarrette/day) 3 (4.2%) 2 (4.5%) 1 (3.8%) 0.64 Gestational pathology 9 (12.9%) 6 (13.6%) 3 (11.5%) 0.8 Gestational age at birth (weeks) 39.4 ± 1.4 39.2 ± 1.5 39.8 ± 1.4 0.1 Number of induced labors 17 (24.6%) 8 (18.6%) 9 (34.6%) 0.16 Estimated fetal weight (g) 3386.4 ± 364.2 3251.1 ± 351.0 3563.0 ± 305.8 0.001 Cause of instrumentation 0.9 Prolonged second stage 55 (78.6%) 34 (77.4%) 20 (77.0% Maternal exhaustion 6 (8.5%) 4 (9.0%) 3 (11.5%) Fetal distress 9 (12.8%) 6 (13.6%) 3 (11.5%) Duration of 1st stage of labor (hours) 7.8 ± 3.2 7.4 ± 3.2 8.4 ± 3.1 0.18 Duration of 2nd stage of labor (hours) 2.3 ± 0.7 2.2 ± 0.7 2.4 ± 0.7 0.07 Number C-sections to complete delivery 5 (7.1%) 0 (0%) 5 (19.2%) 0.005 Number of vacuum pulls 2.4 ± 1.6 1.4 ± 0.5 4.4 ± 1.1 50.0005 Maternal morbidity 1 (1.4%) 0 (0%) 1 (3.8%) 1 Uterine atony 1 (1.4%) 0 (0%) 1 (3.8%) 1 Others 0 (0%) 0 (0%) 0 (0%) Sex of newborn (females) 34 (48.5%) 21 (47.7%) 13 (50%) 0.9 Newborn Weight (g) 3372 ± 432 3272 ± 438 3540 ± 372 0.011 APGAR 1 minute 8.8 ± 1.0 8.9 ± 1.0 8.5 ± 1.1 0.07 APGAR 5 minutes 9.9 ± 0.2 10 ± 0 9.9 ± 0.4 0.06 Umbilical cord artery pH 7.25 ± 0.7 7.26 ± 0.6 7.23 ± 0.5 0.525 Perinatal mortality 0 (0%) 0 (0%) 0 (0%) – Perinatal morbility 2 (2.9%) 0 (0%) 2 (7.7%) 0.135 Control to the intensive care neonatology unit 2 (2.9%) 0 (0%) 2 (7.7%) 0.135 Others 0 (0%) 0 (0%) 0 (0%) Table 2. Intrapartum transperineal ultrasound data in 70 pregnancies requiring vacuum delivery. Variable Total (n ¼ 70) Easy vacuum delivery (n ¼ 44) Difficult-Impossible vacuum delivery (n ¼ 26) p Angle of Progression at rest (◦) 123.8 ± 16.5 132.5 ± 11.6 109.2 ± 12.7 0.0005 ≥120◦ 55.7% (39) 84% (37) 7.6% (2) 0.0005 5120 ◦ 44.3% (31) 15.9% (7) 92.3% (24) 0.0005 Angle of Progression with pushing (◦) 133.5 ± 19.7 143.9 ± 14.6 115.1 ± 12.9 0.0005 ≥120◦ 72.5% (50) 95.4% (42) 30.7% (8) 0.0005 5120 ◦ 27.5% (19) 4.6% (2) 65.3% (17) 0.0005 Head direction at rest Up 62.8% (44) 81.3% (35) 34.6% (9) 0.0005 Horizontal-down 36.2% (25) 18.7% (8) 65.3% (17) 0.0005 Head direction with pushing Up 45 (66.2%) 83.3% (35) 38.4% (10) 0.0005 Horizontal-down 23 (33.8%) 16.7% (7) 61.5% (16) 0.0005 Progression distance at rest (mm) 34.3 ± 16.4 36.9 ± 12.3 30.0 ± 21.1 0.002 Progression distance with pushing (mm) 38.2 ± 12.3 42.7 ± 11.3 30.4 ± 9.8 0.0005 Midline angle at rest (◦) 45.6 ± 26.8 37.6 ± 24.6 57 ± 26.3 0.0001 ≤45◦ 59.1% (39) 71.4% (30) 34.6% (9) 0.0005 445 ◦ 40.9% (27) 28.6% (112) 55.6% (15) 0.0005 Midline angle with pushing (◦) 37.2 ± 26.7 27.6 ± 26.6 57.5 ± 26.5 0.025 ≤45◦ 66.7% (37) 73% (27) 34.6% (9) 0.34 445 ◦ 33.3% (23) 26% (9) 63.4% (17) 0.34 Number of vacuum pulls 2.4 ± 1.6 1.4 ± 0.5 4.4 ± 1.1 0.0005 Figure 3.Angle of Progression ROC curve to predict the difficulty of vaginal delivery with vacuum extraction. Figure 4.The progression distance ROC curve to predict the difficulty of vaginal delivery with vacuum extraction. Table 3. Predictive ability of the difficulty of instrumental delivery with vacuum using intrapartum transperineal ultrasound at rest and with pushing. ITU at rest Cutoffs Sensitivity (%) False-positive rate (%) ITU with pushing Cutoffs Sensitivity (%) False-positive rate (%) AoP 120.5◦ 92.3 11.6 AoP 128◦ 84 9.3 Progression distance 35.5 mm 84.6 39.5 Progression distance 37.5 mm 76.9 32.6 Midline angle 43◦ 70.8 31.7 Midline angle 28◦ 91.7 33.3 Discussion Using ‘‘maternal push’’ before an instrumental-assisted delivery is a usual practice carried out by obstetricians in order to determine the level of the fetal presentation (ACOG fetal station) and its degree of engagement [24]. Dupuis et al. [1] reports that, when vaginal examination was carried out, we often fail in the correct evaluation of these parameters. For this reason, intrapartum transperineal ultrasound has been introduced as an attempt to improve the assessment of the delivery progression [24]. The Food and Drug Administration (FDA) warned of the use of vacuum and potential fetal complications, such as intracranial hematoma and subgaleal hemorrhage [25]. Population studies later reported that intracranial hemorrhage occurred in one per: 1900 spontaneous vaginal births, 860 operative deliveries with vacuum, 664 operative deliveries with forceps and 333 cesarean sections after a failed instrumental delivery [9]. Furthermore, an increase in maternal morbidity is described in operative deliveries when compared with spontaneous ones, existing a significant association between an increase in III and IV degree tears in vacuum and forceps assisted deliveries [2]. Currently we can use ITU to evaluate the progression of the second stage of labor, as well as predict the type of delivery that will take place (spontaneous, instrumental or cesarean). Barbera et al. [15] and Kalache et al. [25] report that an angle of progression ≥120◦ is associated with spontaneous vaginal delivery in 90% of cases. Ghi et al. [19] and Torkildsen et al. [26] describe that an upwards direction of the head, accompanied by an angle of rotation545◦ and a perineum-head distance ≤40 mm predicts spontaneous vaginal delivery in 90% of cases. Youssef et al in 2012 introduced the evaluation of the fetal head-symphysis distance in the second stage of Labor, describing the ease of its assessment and its usefulness to predict the mode of delivery [27]. Ghi et al. report that in spontaneous vaginal birth cases, the angle of progression, progression distance and head–symphysis distance show a significant improvement when evaluated in the second stage of labor, predicting an adequate delivery evolution [28,29]. In the appraisal of ITU’s capacity to predict difficulty of fetal extraction in an operative delivery with vacuum, we identified that, if previous to vacuum placement, an angle of progression ≤120◦, a horizontal or downwards head direction, and a midline angle ≥35◦ was identified, the probability of a ‘‘difficult’’ delivery, thus more than 3 pulls needed to achieve fetal extraction, is of 85% [13]. In an attempt to improve ITU’s predictive capacity, we evaluated these sonographic parameters (angle of progression, progression distance, head direction, midline angle and head-perineum distance) with pushing, observing an adequate intra- (0.99–0.98) and inter- (0.93–0.77) observer correlation [30], enabling it to be applied to clinical practice. Regarding this, Henrich et al. [18] evaluated ITU with pushing, observing that all ‘‘difficult’’ cases in his series (5 cases) had a horizontal or downwards head direction and 60% (3/5 cases) exceeded the infrapubic line. Similarly, Lau et al. [31] described how those cases which ended in vaginal operative delivery with vacuum presented higher progression angles, than those which required cesarean section to complete fetal extraction. Furthermore, Cuerva et al. [20] compared ITU’s parameters at rest and with pushing to predict the difficulty in forceps-assisted deliveries, observing that the best sonographic predictors are angle of progression and head direction, both with pushing, and concluding that an angle of progression4138◦ with pushing is a reliable indicator of easy vaginal delivery with forceps. Comparing ITU’s parameters for the prediction of easy delivery with vacuum, we observed that these vary if realized in rest and with pushing: angle of progression and midline angle vary by a mean of 10◦, progression distance by 6 mm and headperineum distance by 2 mm. However, only the angle of progression, head direction and progression distance, all three of them evaluated with pushing, have proved to be adequate predictors of the difficulty of fetal extraction with vacuum (P50.0005), unlike midline angle and head-peri- neum distance, that do not met the criteria to be considered reliable indicators. If, as mentioned previously, an angle of progression4120◦, an upwards head direction and a midline angle535◦ were identified in an ITU evaluation performed at rest before vacuum application, the probability of facing an easy vacuum delivery (≤ 3 pulls) was485% [13]. As main strengths of our study, a prospective analysis has been highlighted, the fact that intrapartum ultrasound assessment was performed by two senior obstetricians with great experience in sonographic evaluation, and that deliveries were assisted by obstetricians who were blinded to data collected in the intrapartum ultrasound evaluation performed prior to the instrumentation with vacuum. Furthermore, we can now state that the sole identification of an angle of progression with pushing4128◦ traduces a probability of485% of easy vacuum delivery, with a false positive rate of 9.3%. Note that by using this 128◦ as the cutoff of the angle of progression with pushing to identify cases of difficult instrumentation with vacuum, we still have a 16% of cases in which despite we predict a ‘‘difficult’’ instrumentation (5128◦) we will end up facing an ‘‘easy’’ delivery. Once again, we prove that vaginal examination fails to identify the degree of cephalic engagement, according to Dupuis et al. [1] of 15.9% when carried out by experienced obstetricians. In our study we observed that the cases of difficult vacuum deliveries had a mean AoP at rest of 109◦, which according Tutchek et al. studies [32] correspond to a head station of 0.5–1 cm and where operative deliveries should not be performed. Recently, we have published that the presence of an AoP with pushing less than 100◦ is a very unfavorable situation to attempt at vaginal delivery [33]. 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