Predicting operative delivery

Descent of the presenting part assessed with ultrasound

Fetal head descent can be expressed as fetal station and engagement. Station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines. Engagement is based on a transabdominal examination of the proximal part of the fetal head above the pelvic inlet. Clinical examinations are subjective, and objective measurements of descent are warranted. Ultrasound is a feasible diagnostic tool in labor, and fetal lie, station, position, presentation, and attitude can be examined. This review presents an overview of fetal descent examined with ultrasound. Ultrasound was first introduced for examining fetal descent in 1977. The distance from the sacral tip to the fetal skull was measured with A-mode ultrasound, but more convenient transperineal methods have since been published. Of those, progression distance, angle of progression, and head-symphysis distance are examined in the sagittal plane, using the inferior part of the symphysis pubis as reference point. Head-perineum distance is measured in the frontal plane (transverse transperineal scan) as the shortest distance from perineum to the fetal skull, representing the remaining part of the birth canal for the fetus to pass. At high stations, the fetal head is directed downward, followed with a horizontal and then an upward direction when the fetus descends in the birth canal and deflexes the head. Head descent may be assessed transabdominally with ultrasound and measured as the suprapubic descent angle. Many observational studies have shown that fetal descent assessed with ultrasound can predict labor outcome before induction of labor, as an admission test, and during the first and second stage of labor. Labor progress can also be examined longitudinally. The International Society of Ultrasound in Obstetrics and Gynecology recommends using ultrasound in women with prolonged or arrested first or second stage of labor, when malpositions or malpresentations are suspected, and before an operative vaginal delivery. One single ultrasound parameter cannot tell for sure whether an instrumental delivery is going to be successful. Information about station and position is a prerequisite, but head direction, presentation, and attitude also should be considered.

Soft-tissue dystocia due to paradoxical contraction of the levator ani as a cause of prolonged second stage: concept, diagnosis, and potential treatment

Smaller pelvic floor dimensions seem to have been an evolutionary need to provide adequate support for the pelvic organs and the fetal head. Pelvic floor dimension and shape contributed to the complexity of human birth. Maternal pushing associated with pelvic floor muscle relaxation is key to vaginal birth. Using transperineal ultrasound, pelvic floor dimensions can be objectively measured in both static and dynamic conditions, such as pelvic floor muscle contraction and pushing. Several studies have evaluated the role of the pelvic floor in labor outcomes. Smaller levator hiatal dimensions seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Furthermore, smaller levator hiatal dimensions are associated with a higher fetal head station at term of pregnancy, as assessed by transperineal ultrasound. With maternal pushing, most women can relax their pelvic floor, thus increasing their pelvic floor dimensions. Some women contract rather than relax their pelvic floor muscles under pushing, which is associated with a reduction in the anteroposterior diameter of the levator hiatus. This phenomenon is called levator ani muscle coactivation. Coactivation in nulliparous women at term of pregnancy before the onset of labor is associated with a higher fetal head station at term of pregnancy and a longer duration of the second stage of labor. In addition, levator ani muscle coactivation in nulliparous women undergoing induction of labor is associated with a longer duration of the active second stage of labor. Whether we can improve maternal pelvic floor relaxation with consequent improvement in labor outcomes remains a matter of debate. Maternal education, physiotherapy, and visual feedback are promising interventions. In particular, ultrasound visual feedback before the onset of labor can help women increase their levator hiatal dimensions and correct levator ani muscle coactivation in some cases. Ultrasound visual feedback in the second stage of labor was found to help women push more efficiently, thus obtaining a lower fetal head station at ultrasound and a shorter duration of the second stage of labor. The available evidence on the role of any intervention aimed to aid women to better relax their pelvic floor remains limited, and more studies are needed before considering its routine clinical application.

Factors associated with spontaneous vaginal birth in nulliparous women: A descriptive systematic review

PROBLEM

Spontaneous vaginal birth (SVB) rates for nulliparous women are declining internationally.

BACKGROUND

There is inadequate understanding of factors affecting this trend overall and limited large-scale responses to improve women's opportunity to birth spontaneously.

AIM

To undertake a descriptive systematic review identifying factors associated with spontaneous vaginal birth at term, in nulliparous women with a singleton pregnancy.

METHODS

Quantitative studies of all designs, of nulliparous women with a singleton pregnancy and cephalic presentation, who experienced a SVB at term were included. Nine databases were searched (inception to October 2022). Two reviewers undertook quality appraisal; Randomised Controlled Trials (RCTs) with high risk of bias (ROB 2.0) and other designs with (QATSDD) scoring ≤ 50% were excluded.

FINDINGS

Data were abstracted from 90 studies (32 RCTs, 39 cohort, 9 cross-sectional, 4 prevalence, 5 case control, 1 quasi-experimental). SVB rates varied (13%-99%). Modifiable factors associated with SVB included addressing fear of childbirth, low impact antenatal exercise, maternal positioning during second-stage labour and midwifery led care. Complexities arising during pregnancy and regional analgesia were shown to decrease SVB and other interventions, such as routine induction of labour were equivocal.

DISCUSSION

Antenatal preparation (low impact exercise, childbirth education, addressing fear of childbirth) may increase SVB, as does midwifery continuity-of-care. Intrapartum strategies to optimise labour progression emerged as promising areas for further research.

CONCLUSION

Declining SVB rates may be improved through multi-factorial approaches inclusive of maternal, fetal and clinical care domains. However, the variability of SVB rates testifies to the complexity of the issue.

Predictive value of the trans-perineal three-dimensional ultrasound measurement of the pubic arch angle for vaginal delivery

BACKGROUND

Numerous variables are linked to the success of vaginal delivery, including the subpubic arch angle (SPAA) during labor, the importance of which has not yet been fully elucidated.

AIM

To examine the SPAA distributional characteristics and to ascertain SPAA's ability to predict the type and duration of labor.

METHODS

We determined the SPAA and analyzed the corresponding data. We also evaluated the relationship between the SPAA and the mode of delivery and the duration of labor by regression. The present study comprised a total of 301 pregnant women who had given birth at Beijing Tiantan Hospital of the Capital Medical University between January and December of 2021.

RESULTS

Our analysis of 301 pregnant women revealed that the SPAA measured using three-dimensional trans-perineal ultrasound had a minimum angle of 81° and a maximum angle of 122.2°. The angle in the normal vaginal delivery group was greater than that in the labor cesarean group (P = 0.000). The SPAA was a highly significant positive predictor of normal vaginal delivery (P = 0.000) with an area under the curve of 0.782 (P = 0.000; 95%CI: 0.717-0.848). We found the length of the second stage of labor to be positively influenced by the SPAA using linear regression analysis (P = 0.045).

CONCLUSION

The SPAA was a highly significant positive predictor of normal vaginal delivery. The length of the second stage of labor and normal vaginal birth were predicted by SPAA.

Predictive value of the trans-perineal three-dimensional ultrasound measurement of the pubic arch angle for vaginal delivery

BACKGROUND

Numerous variables are linked to the success of vaginal delivery, including the subpubic arch angle (SPAA) during labor, the importance of which has not yet been fully elucidated.

AIM

To examine the SPAA distributional characteristics and to ascertain SPAA’s ability to predict the type and duration of labor.

METHODS

We determined the SPAA and analyzed the corresponding data. We also evaluated the relationship between the SPAA and the mode of delivery and the duration of labor by regression. The present study comprised a total of 301 pregnant women who had given birth at Beijing Tiantan Hospital of the Capital Medical University between January and December of 2021.

RESULTS

Our analysis of 301 pregnant women revealed that the SPAA measured using three-dimensional trans-perineal ultrasound had a minimum angle of 81° and a maximum angle of 122.2°. The angle in the normal vaginal delivery group was greater than that in the labor cesarean group (P = 0.000). The SPAA was a highly significant positive predictor of normal vaginal delivery (P = 0.000) with an area under the curve of 0.782 (P = 0.000; 95%CI, 0.717–0.848). We found the length of the second stage of labor to be positively influenced by the SPAA using linear regression analysis (P = 0.045).

CONCLUSION

The SPAA was a highly significant positive predictor of normal vaginal delivery. The length of the second stage of labor and normal vaginal birth were predicted by SPAA.

Are levator hiatal dimensions in mid-pregnancy associated with mode of delivery?

INTRODUCTION AND HYPOTHESIS

Slow progress of labour is a risk for operative delivery. Smaller levator hiatal dimensions are possible risk factors for slow progress and operative delivery. Our aim was to explore associations between hiatal dimensions antenatally, duration of second stage of labour and mode of delivery.

METHODS

Prospective cohort study of 65 nullipara examined at 20 weeks gestation and 6 months postpartum. Levator hiatal anteroposterior diameter and area were measured using 2D/3D transperineal ultrasound and compared between women with normal vaginal delivery and operative delivery (vacuum or caesarean) using t-test and with Spearman's rank to explore correlations with duration of second stage. ROC analysis established a cut-off for high risk of operative delivery.

RESULTS

Two-dimensional anteroposterior diameter and 3D hiatal area at rest were smaller in women with operative delivery than with normal delivery, 5.0 cm vs. 5.7 cm, p = 0.007 and 18.5 cm² vs. 14.9 cm², p < 0.001. From the ROC curve for 2D anteroposterior diameter, a cut-off of 5.6 cm, (sensitivity = 0.94, specificity = 0.63) and for 3D hiatal area a cut-off of 17.6 cm² (sensitivity = 0.94, specificity = 0.65) predicted operative delivery. We found inverse correlations between second stage of labour and anteroposterior diameter at rest, r = -0.330, contraction, r = -0.365, area at rest, r = -0.324, and contraction, r = -0.521, all p < 0.05.

CONCLUSIONS

Smaller hiatal dimensions at 20 weeks gestation were associated with longer second stage of labour and increased risk of operative delivery in nullipara. A 2D anteroposterior hiatal diameter < 5.6 cm and 3D hiatal area < 17.6 cm² at rest imply increased risk of operative delivery.

Prediction of labor outcome pilot study: evaluation of primiparous women at term

BACKGROUND

Emergency operative delivery is associated with high fetal and maternal morbidity and mortality. It is of high importance to find means to predict the delivery mode before the onset of labor.

OBJECTIVE

This study aimed to investigate the potential of combined sonographic and clinical determination to predict the mode of delivery at term.

STUDY DESIGN

An observational prospective cohort study was deployed in a tertiary maternity hospital (Emergency County Hospital Craiova). Unselected low-risk primiparous pregnant women were evaluated weekly at term for ultrasound determinations (estimated fetal weight, head descent parameters, occiput posterior, cervical length), Bishop score, and maternal characteristics (age, height, weight). A thorough statistical analysis determined which variables were significantly correlated with the delivery mode.

RESULTS

Data from 276 term primiparous women were analyzed. Head descent parameters were strongly and significantly correlated with each other, but only progression distance was correlated with the delivery mode (gestational weeks 37, 38, 41, and the week before delivery). In the week before delivery, measurements of head-to-perineum distance and angle of progression reached almost significant P levels of.055 and.07, respectively. The following variables were significantly correlated with the delivery mode: body mass index in all term evaluations; progression distance for weeks 37 and 38; maternal age for week 39; Bishop score, estimated fetal weight, and occiput posterior for week 40; and body mass index, estimated fetal weight, and progression distance for the week before delivery. We also provided logistic regression equations for each week with correct delivery mode prediction, except for week 38. Cutoff values were established for each significant parameter per week. The cutoff values must be read in conjunction with the area under the curve, which ranged from 0.55 to 0.73, depending on the variable.

CONCLUSION

There are strong and significant correlations among the "head descent" ultrasound measurements at term. Body mass index is predictive of labor outcomes throughout term evaluations. Progression distance and body mass index measured at 37 to 38 weeks' gestation correlate with the delivery mode and apparently can be used to forecast the delivery mode when the pregnancy reaches term. For the week before delivery, measurements of estimated fetal weight and progression distance can be used to forecast the delivery mode, perhaps as part of a policy for pregnant women with prelabor clinical signs. Larger studies with more data, particularly better-balanced data, are needed.

Breech progression angle: new feasible and reliable transperineal ultrasound parameter for assessment of fetal breech descent in birth canal

OBJECTIVE

To assess the feasibility and reliability of transperineal ultrasound in the assessment of fetal breech descent in the birth canal, by measuring the breech progression angle (BPA).

METHODS

Women with a singleton pregnancy with the fetus in breech presentation between 34 and 41 weeks' gestation were recruited. Transperineal ultrasound images were acquired in the midsagittal view for each woman, twice by one operator and once by another. Each operator measured the BPA after anonymization of the transperineal ultrasound images. BPA was defined as the angle between a line running along the long axis of the pubic symphysis and another line extending from the most inferior portion of the pubic symphysis tangentially to the lowest recognizable fetal part in the maternal pelvis. Each operator was blinded to all other measurements performed for each woman. Intra- and interobserver reproducibility of BPA measurement was evaluated using the intraclass correlation coefficient (ICC). To investigate the presence of any bias, intra- and interobserver agreement was also analyzed using Bland-Altman analysis. Student's t-test and Levene's W₀ test were used to investigate whether a number of different clinical factors had an effect on systematic differences and homogeneity, respectively, between BPA measurements.

RESULTS

Overall, 44 women were included in the analysis. BPA was measured successfully by both operators on all images. Both intra- and interobserver agreement analyses showed excellent reproducibility in BPA measurement, with ICCs of 0.88 (95% CI, 0.80-0.93) and 0.83 (95% CI, 0.71-0.90), respectively. The mean difference between measurements was 0.4° (95% CI, -1.4 to 2.2°) for intraobserver repeatability and -0.4° (95% CI, -2.6 to 1.8°) for interobserver repeatability. The upper limits of agreement were 12.0° (95% CI, 8.9-15.1°) and 13.6° (95% CI, 9.9-17.3°) for intra- and interobserver repeatability, respectively. The lower limits of agreement were -11.2° (95% CI, -14.3 to -8.1°) and -14.4° (95% CI, -18.2 to -10.7°) for intra- and interobserver repeatability, respectively. No systematic difference between BPA measurements was found on either intra- or interobserver agreement analysis. None of the clinical factors examined (maternal body mass index, maternal age, gestational age at the ultrasound scan and parity) showed a statistically significant effect on intra- or interobserver reliability.

CONCLUSIONS

BPA represents a new feasible and highly reproducible measurement for the evaluation of fetal breech descent in the birth canal. Future studies assessing its usefulness in the prediction of successful external cephalic version and breech vaginal delivery are needed. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

The maternal pelvic floor and labor outcome

Vaginal birth is the major cause of pelvic floor damage. The development of transperineal ultrasound has improved our understanding of the relationship between vaginal birth and pelvic floor dysfunction. The female pelvic floor dimensions and function can be assessed reliably in pregnant women. Maternal pushing associated with pelvic floor muscle relaxation is the central requirement of vaginal birth. Many studies have evaluated the role of the pelvic floor on labor outcomes. Smaller levator hiatal dimensions and incomplete or absent levator ani muscle relaxation seem to be associated with a longer duration of the second stage of labor and a higher risk of cesarean and operative deliveries. Here, we presented an overview of the current knowledge of the correlation between female pelvic floor dimension and function, as assessed by transperineal ultrasound, and labor outcome.

Fetal head progression and regression on maternal pushing at term and labor outcome

OBJECTIVES

The aim of our study was two-fold. First, to evaluate the association between the change in the angle of progression (AoP) on maternal pushing and labor outcome. Second, to assess the incidence and clinical significance of the reduction of AoP on maternal pushing.

METHODS

This was a prospective cohort study of nulliparous women with singleton pregnancy at term. AoP was measured at rest and on maximum Valsalva maneuver before the onset of labor, and the difference between AoP on maximum Valsalva and that at rest (ΔAoP) was calculated for each woman. Following delivery and data collection, we assessed the association between ΔAoP and various labor outcomes, including Cesarean section (CS), duration of the first, second and active second stages of labor, Apgar score and admission to the neonatal intensive care unit (NICU). The prevalence of women with reduction of AoP on maximum Valsalva maneuver (AoP-regression group) was calculated and its association with the mode of delivery and duration of different stages of labor was assessed.

RESULTS

Overall, 469 women were included in the analysis. Among these, 273 (58.2%) had spontaneous vaginal birth, 65 (13.9%) had instrumental delivery and 131 (27.9%) underwent CS. Women in the CS group were older, had narrower AoP at rest and on maximum Valsalva, higher rate of epidural administration and lower 1-min and 5-min Apgar scores in comparison with the vaginal-delivery group. ΔAoP was comparable between the two groups. On Pearson's correlation analysis, AoP at rest and on maximum Valsalva maneuver had a significant negative correlation with the duration of the first stage of labor. ΔAoP showed a significant negative correlation with the duration of the active second stage of labor (Pearson's r, -0.125; P = 0.02). Cox regression model analysis showed that ΔAoP was associated independently with the duration of the active second stage (hazard ratio, 1.014 (95% CI, 1.003-1.025); P = 0.012) after adjusting for maternal age and body mass index. AoP reduction on maximum Valsalva was found in 73 (15.6%) women. In comparison with women who showed no change or an increase in AoP on maximum Valsalva, the AoP-regression group did not demonstrate significant difference in maternal characteristics, mode of delivery, rate of epidural analgesia, duration of the different stages of labor or rate of NICU admission.

CONCLUSIONS

In nulliparous women at term before the onset of labor, narrower AoP at rest and on maximum Valsalva, reflecting fetal head engagement, is associated with a higher risk of Cesarean delivery. The increase in AoP from rest to Valsalva, reflecting more efficient maternal pushing, is associated with a shorter active second stage of labor. Fetal head regression on maternal pushing is present in about 16% of women and does not appear to have clinical significance. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

The usefulness of ultrasound before induction of labor

The indications for induction of labor have been consistently on the rise. These indications are mainly medical (maternal or fetal) or social or related to convenience or maternal preferences. With the increase in the prevalence of these indications, the incidence rates of induction of labor are expected to rise continuously. This poses a substantial workload and financial burden on maternity healthcare systems. Failure rates of induction of labor are relatively high, especially when considering the maternal, fetal, and neonatal risks associated with emergency cesarean deliveries in cases of failure. Therefore, it is essential for obstetricians to carefully select women who are eligible for induction of labor, particularly those with no clinical contraindication and who have a reasonable chance of ending up with a successful noncomplicated vaginal delivery. Ultrasound has an established role in the various areas of obstetrical care. It is available, accessible, easy to perform, and acceptable to the patient. In addition, the learning curve for skillful obstetrical ultrasound scanning is rather easy to fulfill. Ultrasound has always had an important role in the assessment of maternal and fetal well-being. Indeed, it has been extensively explored as a reliable, reproducible, and objective tool in the management of labor. In this review, we aimed to provide a comprehensive update on the different applications and uses of ultrasound before induction of labor for the prediction of its success and the potential improvement of its health-related maternal and fetal outcomes.

Transperineal ultrasound assessment of maternal pelvic floor at term and fetal head engagement

OBJECTIVES

To evaluate the association between pelvic floor dimensions in nulliparous women at term and fetal head engagement, as assessed by transperineal ultrasound.

METHODS

This was a prospective observational study of nulliparous women at term. Before the onset of labor, transperineal ultrasound was used to measure the anteroposterior diameter (APD) of the levator hiatus and the angle of progression (AoP) at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver (before and after visual feedback). We assessed the correlation between pelvic floor static and dynamic dimensions (levator hiatal APD and levator ani muscle coactivation) and AoP, which is an objective index of fetal head engagement.

RESULTS

In total, 282 women were included in the analysis. Among these, 211 (74.8%) women had a vaginal delivery while 71 (25.2%) had a Cesarean delivery. AoP was narrower in the Cesarean-delivery group at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva, whereas no differences in levator hiatal APD were found between the two groups. We found a negative correlation between levator hiatal APD at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva and the duration of the second stage of labor. There was a positive correlation between AoP and levator hiatal APD on maximum Valsalva maneuver after visual feedback (r = 0.15, P = 0.01). Women with levator ani muscle contraction on Valsalva maneuver (i.e. coactivation), both pre and post visual feedback, had a narrower AoP at rest and on maximum Valsalva. After visual feedback, women with levator ani muscle coactivation had a longer second stage of labor than did those without (80.8 ± 61.4 min vs 62.9 ± 43.4 min (P = 0.04)).

CONCLUSIONS

Smaller pelvic floor dimensions and levator ani muscle coactivation are associated with higher fetal head station and with a longer second stage of labor in nulliparous women at term. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

The dynamic change of the anteroposterior diameter of the levator hiatus under Valsalva maneuver at term and labor outcome

AIM

The aim of the present study was to evaluate the correlation between the proportional change of anteroposterior diameter (APD) of levator hiatus from rest to maximum Valsalva maneuver in nulliparous women at term and labor outcome.

METHODS

We prospectively recruited nulliparous women at term before the onset of labor. Women underwent a two-dimensional transperineal ultrasound, measuring the APD of the levator hiatus at rest and under maximum Valsalva's maneuver. APD change from rest to maximum Valsalva was described both in terms of absolute figures and proportional change. Correlation of APD change with the mode of delivery and with labor durations was assessed.

RESULTS

Overall, 486 women were included in the analysis. No significant association between change in APD and the mode of delivery. We found a significant negative correlation between change of APD from rest to Valsalva and the duration of active second stage both in terms of absolute change (Pearson's r = -0.138, P = .009) and in terms of proportional change (Pearson's r = -0.154, P = .004). Survival outcomes based on Cox-regression model showed that APD was independently associated with the duration of active second stage of labor after adjusting for epidural analgesia, maternal age and body mass index (hazard ratio, 1.008; 95% confidence interval, 1.001-1.016; P = .04) CONCLUSION: Women with higher increase of the anteroposterior diameter of the levator hiatus from rest to Valsalva have a shorter active second stage of labor.

Descent of fetal head during active pushing: secondary analysis of prospective cohort study investigating ultrasound examination before operative vaginal delivery

OBJECTIVES

To investigate if descent of the fetal head during active pushing is associated with duration of operative vaginal delivery, mode of delivery and neonatal outcome in nulliparous women with prolonged second stage of labor.

METHODS

This was a prospective cohort study of nulliparous women with prolonged second stage of labor, conducted between November 2013 and July 2016 in five European countries. Fetal head descent was measured using transperineal ultrasound. Head-perineum distance (HPD) was measured between contractions and on maximum contraction during active pushing, and the difference between these values (ΔHPD) was calculated. The main outcome was duration of operative vaginal delivery, estimated using survival analysis to calculate hazard ratios (HRs) for vaginal delivery, with values > 1 indicating a shorter duration. HR was adjusted for prepregnancy body mass index, maternal age, induction of labor, augmentation with oxytocin and use of epidural analgesia. Pregnancies were grouped according to ΔHPD quartile, and delivery mode and neonatal outcome were compared between groups.

RESULTS

The study population comprised 204 women. Duration of vacuum extraction was shorter with increasing ΔHPD. Estimated mean duration was 10.0, 9.0, 8.8 and 7.5 min in pregnancies with ΔHPD in the first to fourth quartiles, respectively, and the adjusted HR for vaginal delivery, using increasing ΔHPD as a continuous variable, was 1.04 (95% CI, 1.01-1.08). Mean ΔHPD was 7 mm (range, -10 to 37 mm). ΔHPD was either negative or ≤ 2 mm in the lowest quartile. In this group, 7/50 (14%) pregnancies were delivered by Cesarean section, compared with 8/154 (5%) of those with ΔHPD > 2 mm (P < 0.05). There was no significant association between umbilical artery pH < 7.10 or 5-min Apgar score < 7 and ΔHPD quartile.

CONCLUSION

Minimal or no fetal head descent during active pushing was associated with longer duration of operative vaginal delivery and higher frequency of Cesarean section in nulliparous women with prolonged second stage of labor. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Assessment of labor progression by intrapartum ultrasonography among term nulliparous women

OBJECTIVE

To assess cervical dilation, fetal head station, and fetal head position by intrapartum ultrasonography and to compare the approach with digital vaginal examination (DVE).

METHODS

An observational study conducted from October 2015 to January 2017 among term nulliparous women in active labor at a tertiary hospital in Delhi, India. Cervical dilation, head station, and head position were assessed by DVE, followed by ultrasonography within 10 minutes. The women's preference was also evaluated.

RESULTS

Overall, 458 observations were obtained for 215 women. Cervical dilation measured by DVE was strongly correlated with ultrasonography findings (intraclass correlation coefficient, 0.945; 95% confidence interval, 0.932-0.956; κ=0.837; P<0.001). Data for fetal head station and head position showed a fair correlation (κ=0.353 and κ=0.554, respectively; both P<0.001). The majority of women (186/215, 87%) reported a preference for ultrasonography over DVE for assessment of labor progression in a future pregnancy.

CONCLUSION

Intrapartum ultrasonography was preferred as an objective assessment tool for labor progression among term nulliparous women and therefore should be practiced in all labor rooms. Further studies on interobserver variation are recommended to establish the reproducibility of intrapartum assessment by ultrasonography.

Levator ani muscle coactivation at term is associated with longer second stage of labor in nulliparous women

OBJECTIVE

To assess the effect of levator ani muscle (LAM) coactivation at term on outcome of labor in nulliparous women.

METHODS

This was a prospective study of 284 low-risk nulliparous women with a singleton pregnancy at term recruited before the onset of labor. The anteroposterior diameter of the levator hiatus was measured in each woman on transperineal ultrasound at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver before and after visual feedback. LAM coactivation was defined as a reduction in the anteroposterior diameter of the levator hiatus on maximum Valsalva maneuver in comparison with that at rest. The association of pelvic hiatal diameter values and LAM coactivation with mode of delivery and duration of labor was assessed.

RESULTS

No significant difference was found between women who underwent Cesarean delivery and those who had a vaginal delivery with regard to the anteroposterior diameter of the levator hiatus at rest, on pelvic floor muscle contraction and on Valsalva maneuver. Longer second stage of labor was associated with shorter anteroposterior diameter of the levator hiatus on all assessments, but in particular at rest and on Valsalva both before and after visual feedback. LAM coactivation was found in 89 (31.3%) and 75 (26.4%) women before and after visual feedback, respectively. Post visual feedback, women with LAM coactivation had a significantly longer second stage of labor than did those without LAM coactivation (83 ± 63 vs 63 ± 42 min; P = 0.006). On Cox regression analysis, LAM coactivation post visual feedback was an independent predictor of longer second stage of labor (adjusted hazard ratio, 1.499 (95% CI, 1.076-2.087); P = 0.017).

CONCLUSION

LAM coactivation in nulliparous women at term is associated with a longer second stage of labor. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Contraction of the levator ani muscle during Valsalva maneuver (coactivation) is associated with a longer active second stage of labor in nulliparous women undergoing induction of labor

BACKGROUND

The Valsalva maneuver is normally accompanied by relaxation of the levator ani muscle, which stretches around the presenting part, but in some women the maneuver is accompanied by levator ani muscle contraction, which is referred to as levator ani muscle coactivation. The effect of such coactivation on labor outcome in women undergoing induction of labor has not been previously assessed.

OBJECTIVE

The aim of the study was to assess the effect of levator ani muscle coactivation on labor outcome, in particular on the duration of the second and active second stage of labor, in nulliparous women undergoing induction of labor.

STUDY DESIGN

Transperineal ultrasound was used to measure the anteroposterior diameter of the levator hiatus, both at rest and at maximum Valsalva maneuver, in a group of nulliparous women undergoing induction of labor in 2 tertiary-level university hospitals. The correlation between anteroposterior diameter of the levator hiatus values and levator ani muscle coactivation with the mode of delivery and various labor durations was assessed.

RESULTS

In total, 138 women were included in the analysis. Larger anteroposterior diameter of the levator hiatus at Valsalva was associated with a shorter second stage (r = -0.230, P = .021) and active second stage (r = -0.338, P = .001) of labor. Women with levator ani muscle coactivation had a significantly longer active second stage duration (60 ± 56 vs 28 ± 16 minutes, P < .001). Cox regression analysis, adjusted for maternal age and epidural analgesia, demonstrated an independent significant correlation between levator ani muscle coactivation and a longer active second stage of labor (hazard ratio, 2.085; 95% confidence interval, 1.158-3.752; P = .014). There was no significant difference between women who underwent operative delivery (n = 46) when compared with the spontaneous vaginal delivery group (n = 92) as regards anteroposterior diameter of the levator hiatus at rest and at Valsalva maneuver, nor in the prevalence of levator ani muscle coactivation (10/46 vs 15/92; P = .49).

CONCLUSION

Levator ani coactivation is associated with a longer active second stage of labor.

Head progression distance during the first stage of labor as a predictor for delivery outcome

Objectives: To assess if measurement of the head progression distance (PD) during the first stage of labor in nulliparous women can predict the delivery method.Methods: A prospective study was conducted on consecutive nulliparous women beyond 37 week's gestation during the first stage of labor. Transperineal ultrasound was performed to assess the PD. Analysis was performed on the relationships between PD during rest and during voluntary pushing and the fetal and maternal characteristics, delivery mode, and immediate postnatal outcomes.Results: Eighty seven suitable nulliparous women were suitable for analysis. PD was found to be significantly longer in women who delivered vaginally (VD) compared to those who underwent a cesarean section (CS) for obstructed labor: PD at rest was 2.51 ± 1.71 cm in women who delivered vaginally compared to 1.48 ± 1.9 cm in women who delivered by CS (p = .01). The PD during pushing was 3.43 ± 1.8 cm for a VD compared to 1.5 ± 2.1 cm for CS (p = .015). Logistic regression and receiver-operating characteristics curve analysis demonstrated a moderate predictive value of PD with respect to the mode of delivery (area under the curve was 0.67 during both resting and pushing period).Conclusion: PD measurements during the first stage of labor among nulliparous women differ significantly both in rest and during pushing between patients who delivered vaginally compared to CS and can therefore assist in predicting the mode of delivery.

Is ultrasound measured fetal biometry predictive of intrapartum caesarean section for failure to progress?

BACKGROUND

There are global concerns regarding excessive caesarean rates, which could be reduced by identification of risk factors leading to preventative measures such as induction of labour.

AIMS

This study aims to describe the association between antenatal ultrasound and emergency caesarean section for: (i) failure to progress; (ii) other indications; and (iii) any indication.

MATERIALS AND METHODS

Women who had an ultrasound in pregnancy between 36^(+0/7) to 38^(+6/7) weeks at Royal Prince Alfred Hospital from January 2005 to June 2009 were included. Ultrasound parameters were linked to clinical parameters from the maternity database. Missing clinical data were imputed and multiple logistic regression performed.

RESULTS

Fetal biometry data were available for 2006 pregnancies. After adjusting for maternal age, height, body mass index, parity, previous caesarean section and diabetes, caesarean section for failure to progress was associated with estimated fetal weight (odds ratio (OR) 2.24 (95% CI: 1.76-2.84) per 500 g increase); or biparietal diameter (OR 1.51 (1.16-1.97) per 5 mm increase) and abdominal circumference (OR for the 4th quartile (>75th centile) compared with the 10-25th centile group was 2.09 (1.13-3.85)).* There were also non-linear associations between components of fetal biometry and caesarean section for fetal distress and for any indication.

CONCLUSIONS

Components of fetal biometry in the third trimester are associated with intrapartum caesarean section for failure to progress. These parameters could be incorporated into models to predict emergency caesarean section which could lead to implementation of preventative strategies. *[Corrections added on 29 January 2018, after first online publication, '(OR for the 4th quartile (>7th centile)' has been changed to '(OR for the 4th quartile (>75th centile)'.].

Using theory of planned behavior for prediction of delivery mode among pregnant women: a theory-based cross-sectional research

Background Nowadays, in Iran cesarean rates have increased from the recommended level of the World Health Organization (WHO). Objectives The objective of the present study was to determine which theory of planned behavior (TPB) constructs predict intentions and delivery mode among pregnant women. Methods One hundred and four pregnant nulliparous women in their third trimesters of pregnancy referred to Semirom health care centers were investigated based on census reports. The data were collected by valid and reliable questionnaire based on the TPB constructs and analyzed by SPSS16. Results In examining predictors using linear regression analysis to choose normal vaginal delivery (NVD), all constructs of TPB, including attitude toward NVD (p < 0.0001), subjective norms (p < 0.05) and perceived behavioral control (p < 0.001) were significantly correlated. Finally, after telephone follow-up with the women who had delivered newborns on their delivery method, it was found that 71.15% had a NVD and 28.14% had a cesarean delivery. Conclusions Regarding the effect of attitude to NVD, subjective norms and perceived behavioral control in NVD intention and its crucial role in anticipating the final delivery method, it is recommended considering these constructs in designing educational interventions for safe delivery in the investigated area.

Prediction of time to delivery by transperineal ultrasound in second stage of labor

OBJECTIVE

To investigate whether the transperineal sonographic (TPS) parameters angle of progression (AoP) and midline angle (MLA) can predict the time remaining in the second stage of labor.

METHODS

We evaluated prospectively women with a singleton pregnancy in cephalic presentation at term between October 2013 and September 2014. TPS volumes were obtained immediately after confirmation by digital vaginal examination of a fully dilated cervix. AoP and MLA were measured offline by analyzing the ultrasound volumes. Progression of labor was evaluated every hour during the second stage. The associations of AoP and MLA with the interval between TPS assessment and delivery were evaluated using multivariable Cox proportional hazards analyses in nulliparous and parous women separately.

RESULTS

A total of 557 women were evaluated. An AoP ≥ 160° (adjusted hazard ratio (aHR), 2.52 (95% CI, 1.98-3.19)) and MLA ≤ 10° (aHR, 1.79 (95% CI, 1.35-2.34)) in nulliparous women and an AoP ≥ 150° (aHR, 1.86 (95% CI, 1.34-2.57)) and MLA ≤ 20° (aHR, 1.69 (95% CI, 1.21-2.34)) in parous women were significantly associated with the remaining time in labor. The positive/negative likelihood ratios of AoP, MLA, clinical station (fetal head descent as observed by digital examination) and clinical rotation (fetal head rotation as observed by digital examination) at these cut-off points were 3.6/0.6, 2.0/0.6, 1.6/0.6 and 1.6/0.8, respectively, in nulliparous women, and 2.4/0.6, 1.3/0.7, 7.6/0.5 and 5.2/0.7, respectively, in parous women.

CONCLUSION

TPS assessment of AoP and MLA in the second stage of labor was useful for predicting the time remaining in labor and had higher predictive value than did digital vaginal examination in nulliparous women. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Pre-induction translabial ultrasound measurements in predicting mode of delivery compared to bishop score: a cross-sectional study

Background

By increased concerns about the accuracy of the traditional methods to predict outcomes after induction of labor, developing new standards has a great clinical importance. Here, we compared the predictive value of translabial ultrasound measurements with Bishop Score to determine the suitability of induction of labor.

Methods

A homogenous population of primigravid women was recruited. Induction of labor was performed with low-dose infusion of oxytocin. Translabial ultrasound and assessment of Bishop Score were performed by two different obstetricians. Receiver–operating characteristics curves were obtained to measure area under curve and subsequently, test sensitivity of each method.

Results

One hundred women entered the investigation. Maternal body mass index was significantly higher among candidates of Cesarean section (P: 0.02). Maternal age and fetus weight, gender and occiput position were not determinants of outcomes of induction of labor. Cervical length and fetal head-pubis symphysis distance measured by translabial ultrasound had a test sensitivity of 90 and 88 %, respectively which were slightly higher than sensitivity of Bishop score (84 %).

Conclusion

This study demonstrates that translabial measurements can be a suitable alternative method to monitor labor progress with an admissible predictive value compared with Bishop Score. It is a non-invasive method which provides valuable objective measurements and can be better accepted by women when considering the painful process which is required in evaluating Bishop Score.

Ultrasound examination at term for predicting the outcome of delivery in women with a previous cesarean section

OBJECTIVE

To evaluate if ultrasound variables at term are associated with the mode of delivery in women with previous cesarean section (PCS).

METHODS

This was a prospective study of singleton pregnant women who planned a trial of vaginal birth after cesarean delivery. Cervical length, posterior cervical angle, head-perineum distance, and estimated fetal weight were measured at 37-39 weeks of gestation.

RESULTS

One hundred forty-four pregnancies were examined and vaginal delivery was achieved in 98 women (73%). Logistic regression analysis identified cervical length, head-perineum distance, age, previous vaginal delivery, previous cesarean for dystocia, and Bishop score as predictors of vaginal delivery. Combining ultrasound and clinical parameters, two models for risk scoring that differ in the variable Bishop score or cervical length were constructed. The AUC of these models was 0.867 and 0.855, respectively.

CONCLUSIONS

In women with a PCS, measurement of cervical length and head-perineum distance at term is associated with the mode of delivery. A combination of clinical and sonographic parameters at term can predict the likelihood of vaginal delivery.

Prognostic models in obstetrics: available, but far from applicable

Health care provision is increasingly focused on the prediction of patients' individual risk for developing a particular health outcome in planning further tests and treatments. There has been a steady increase in the development and publication of prognostic models for various maternal and fetal outcomes in obstetrics. We undertook a systematic review to give an overview of the current status of available prognostic models in obstetrics in the context of their potential advantages and the process of developing and validating models. Important aspects to consider when assessing a prognostic model are discussed and recommendations on how to proceed on this within the obstetric domain are given. We searched MEDLINE (up to July 2012) for articles developing prognostic models in obstetrics. We identified 177 papers that reported the development of 263 prognostic models for 40 different outcomes. The most frequently predicted outcomes were preeclampsia (n = 69), preterm delivery (n = 63), mode of delivery (n = 22), gestational hypertension (n = 11), and small-for-gestational-age infants (n = 10). The performance of newer models was generally not better than that of older models predicting the same outcome. The most important measures of predictive accuracy (ie, a model's discrimination and calibration) were often (82.9%, 218/263) not both assessed. Very few developed models were validated in data other than the development data (8.7%, 23/263). Only two-thirds of the papers (62.4%, 164/263) presented the model such that validation in other populations was possible, and the clinical applicability was discussed in only 11.0% (29/263). The impact of developed models on clinical practice was unknown. We identified a large number of prognostic models in obstetrics, but there is relatively little evidence about their performance, impact, and usefulness in clinical practice so that at this point, clinical implementation cannot be recommended. New efforts should be directed toward evaluating the performance and impact of the existing models.

Prediction of delivery mode by ultrasound-assessed fetal position in nulliparous women with prolonged first stage of labor

OBJECTIVES

To ascertain if fetal head position on transabdominal ultrasound is associated with delivery by Cesarean section in nulliparous women with a prolonged first stage of labor.

METHODS

This was a prospective observational study performed at Stavanger University Hospital, Norway, and Addenbrooke's Hospital, Cambridge, UK, between January 2012 and April 2013. Nulliparous pregnant women with a singleton cephalic presentation at term and prolonged labor had fetal head position assessed by ultrasound. The main outcome was Cesarean section vs vaginal delivery, and secondary outcomes were association of fetal head position with operative vaginal delivery and duration of remaining time in labor.

RESULTS

Fetal head position was assessed successfully by ultrasound examination in 142/150 (95%) women. In total, 19/50 (38%) women with a fetus in the occiput posterior (OP) position were delivered by Cesarean section compared with 16/92 (17%) women with a fetus in a non-OP position (P = 0.01). On multivariable logistic regression analysis, the OP position predicted delivery by Cesarean section with an odds ratio (OR) of 2.9 (95% CI, 1.3-6.7; P = 0.01) and induction of labor with an OR of 2.4 (95% CI, 1.0-5.6; P = 0.05). Fetal head position was not associated with operative vaginal delivery or with remaining time in labor. The agreement between a digital and an ultrasound assessment of OP position was poor (Cohen's kappa = 0.19; P = 0.18).

CONCLUSION

OP fetal head position assessed by transabdominal ultrasound was significantly associated with delivery by Cesarean section.

Intrapartum sonographic signs: new diagnostic tools in malposition and malrotation

In the past years, numerous studies have been published on the use of ultrasound during labor, showing this is an effective, accurate and objective tool for the assessment of the fetal head position and station. Literature affirmed that traditional transvaginal digital examination is highly subjective and dependent on the operator's experience. On the contrary, the use of intrapartum suprapubic transabdominal ultrasound can improve accuracy in determination of fetal head position and the precise knowledge of the location of specific fetal head landmarks in relationship to maternal pelvis. Intrapartum ultrasound will assist obstetricians in the diagnosis of normal labor progression, suggesting when medical and or operative intervention should be taken in case of complications. During each fetal head movement, there is a very specific relationship between fetal head landmarks and well-identified maternal structures, so the ultrasound diagnosis is performed step by step. In this review, we summarized the clinical situation of the fetal head in the pelvis and the relative ultrasonographic signs. Moreover, we collected all the ultrasonographic measures to diagnose the fetal head progression and rotations in the birth canal.

Measurement of subpubic arch angle by three-dimensional transperineal ultrasound and impact on vaginal delivery

OBJECTIVES

To assess whether antepartum measurement of the subpubic arch angle (SPAA) as a parameter of the bony pelvic outlet can predict vaginal delivery.

METHODS

Between January 2007 and June 2011, 625 nulliparous women with a singleton pregnancy were recruited from the antenatal clinic to be interviewed and have a four-dimensional transperineal ultrasound examination. Ultrasound examinations were performed between 34 and 36 weeks of gestation. Volume ultrasound data were saved for offline analysis, blinded against all other data. The SPAA was measured in the axial plane and logistic regression analysis was used to examine the association between SPAA and outcomes of vaginal delivery vs Cesarean section in the second stage of labor, and normal vs assisted vaginal delivery. The association between SPAA and the duration of second stage of labor was also analyzed.

RESULTS

Of the 625 women recruited initially, 14 ultrasound data files could not be retrieved, providing a total of 611 ultrasound images for measurement of SPAA. Complete obstetric and ultrasound data were obtained from 593 patients. Mean SPAA was 109.3° (range, 65.6-131.6°). There was no association between SPAA and the odds of a vaginal delivery (odds ratio, 1.01 (95% CI, 0.97-1.06)). However, there was evidence of an association between SPAA and duration of second stage of labor within the subgroup of women with a normal vaginal delivery (cause-specific hazard ratio, 1.02 (95% CI, 1.01-1.03); P = 0.003).

CONCLUSIONS

SPAA is not useful for predicting vaginal delivery; however, there is an association between this parameter and the duration of the second stage of labor.

Manipal Cervical Scoring System by Transvaginal Ultrasound in Predicting Successful Labour Induction

INTRODUCTION

Induction of labour (IOL) nowadays is a common procedure in obstetric practice. The success of IOL largely depends upon "favourability" or "readiness" cervix which is traditionally assessed by manual examination and Scored as Bishop Score. However, this method is limited by subjectivity and reproducibility and though done in all the patients prior to IOL, several studies have demonstrated poor correlation between Bishop Score and outcome of labour.

OBJECTIVE

To evaluate the role of preinduction transvaginal ultrasonographic (TVS) cervical assessment in predicting labour outcome and to compare its performance against Bishop Score in patients undergoing induction of labour (IOL).

SETTING

A tertiary medical college hospital in Southern India.

DESIGN

Prospective observational and investigational study.

MATERIALS AND METHODS

Transvaginal ultrasound was performed in 131 patients who underwent labour induction at term with intact membranes and live fetus. Bishop Score was assessed by pervaginal examination and was compared with preinduction TVS cervical Score (parameters being cervical length, funneling, position of cervix and distance of presenting part from external os). Labour was induced within one hour of cervical assessment. The labour induction was considered successful if patient could get into active labour i.e., onset of regular uterine contractions (at interval of 2-3 minutes) and cervical dilatation of 4 cm or greater within 24 hours of induction.

RESULTS

Labour induction was successful in 86.9% of patients. At cut off Scores of ≥ 4, TVS cervical Score performed better than Bishop Score (Sensitivity 77% vs. 65%, Specificity 93% vs. 86%). ROC analysis indicated that Area Under Curve (AUC) was more for TVS Score (0.90, 95% CI 0.84 - 0.95), compared to Bishop Score. It was found that an increase in cervical length and distance from the os by 1 mm from their means were associated with an increase in odds for failure of induction and there by caesarean delivery by 6.5% and 11% respectively.

CONCLUSION

In women experiencing labour induction, transvaginal ultrasound score comprising of five different parameters indicated success of induction better than Bishop Score. Further, two of its components (longer cervical length and increased distance of presenting part from external os) demonstrated significant and independent prediction of the likelihood of failure of induction and risk of operative delivery.

Relationship between detection of the cervical gland area during the late third trimester and necessity for induction of labor to prevent post-term delivery

OBJECTIVES

With the maturation of the cervical canal during pregnancy, the cervical gland area (CGA) as observed on transvaginal ultrasonography is gradually obscured. The aim of this study was to elucidate the significance of CGA in the late third trimester as a determinant of the outcome of labor.

METHODS

We investigated 123 primiparous women with singleton pregnancies at 36-41 weeks' gestation. The women were divided into two groups: a normal delivery group (93 women), which had vaginal delivery without medical intervention, and an induction of labor group (30 women), which required induction of labor after 41 weeks and 0 day. At outpatient prenatal checkups, the Bishop score (BS) was assessed by pelvic examination, and cervical length (CL) and CGA were evaluated by transvaginal ultrasonography. The relationship between each parameter and induction of labor was retrospectively determined and compared.

RESULTS

Time-dependent assessment of each outcome determinant showed that the CGA detection rate was higher and the CL was longer in the induction of labor group from 3 weeks to 1 week before delivery at a significant level (P < 0.05); however, the BS was significantly lower in the induction of labor group only at 1 week before delivery (P < 0.05). When multiple logistic regression analysis of the necessity of induction of labor was conducted using BS, CL, and CGA parameters as explanatory variables at 1 week before delivery, CGA alone was shown to be an independent predictor of induction of labor (OR = 6.1, 95 % CI 2.3-16.2).

CONCLUSION

The present study suggests that in the late third trimester, evaluation of CGA with transvaginal ultrasonography is most useful in predicting the necessity of induction of labor to prevent post-term delivery.

Levator hiatus dimensions in late pregnancy and the process of labor: a 3- and 4-dimensional transperineal ultrasound study

OBJECTIVE

The objectives of the investigation were to study the association between levator hiatus dimensions in late pregnancy and both the length of second stage of labor and also the delivery mode in women delivering their first child.

STUDY DESIGN

In this cohort study, 231 nulliparous women were examined with 3- and 4-dimensional transperineal ultrasonography at 37 weeks of gestation. The anteroposterior, transverse diameter, and the area of levator hiatus were measured at rest, during levator ani muscle contraction, and during Valsalva maneuver. The second stage of labor was divided into passive and active second stage and delivery modes into normal vaginal or instrumental deliveries. Spearman correlation coefficient, independent-sample t test, and standard logistic regression were used for analysis.

RESULTS

Larger levator hiatus dimensions at rest and during contraction at 37 weeks of gestation correlated with a shorter duration of the active second stage in women with normal vaginal delivery (Spearman correlation coefficient, -0.13 to -0.35, P ≤ .08). Women having normal vaginal deliveries had significantly larger transverse diameter at rest, during contraction, and during Valsalva maneuver compared with women having instrumental deliveries (mean difference, 0.29; 95% confidence interval (CI), 0.16-0.41; mean difference, 0.33; 95% CI, 0.21-0.44 and mean difference, 0.24; 95% CI, 0.06-0.42; P < .05). The same was true for the levator hiatus area at rest and during contraction (mean difference, 1.22; 95% CI, 0.37-2.07 and mean difference, 0.84; 95% CI, 0.22-1.46; P < .01). These estimates were unchanged by adjustments in the logistic regression analysis.

CONCLUSION

Larger levator hiatus dimensions in late pregnancy had a significant association with a shorter active second stage of labor and normal vaginal delivery.

Intrapartum sonographic assessment of labor

Fetal head progression during labor is difficult to assess. Digital examination has been shown to be an inaccurate method. Utilizing the ultrasound technology in the delivery room can standardize the way we assess head progression. Intrapartum ultrasound is applicable, for the assessment of the progression of labor and assists the obstetrician, in decision making regarding the need for an assisted delivery. This article summarizes the latest studies regarding the usage of ultrasound in the delivery room and the measurements that are used during delivery.

Can angle of progression in pregnant women before onset of labor predict mode of delivery?

OBJECTIVES

The angle of progression (AOP), measured by transperineal ultrasound, has been used to assess fetal head descent during labor. Our aim was to assess whether, before onset of labor, parous women have a narrower AOP than do nulliparous women and if a narrow AOP is associated with a higher rate of Cesarean delivery.

METHODS

In this prospective, observational study, we performed transperineal ultrasound in pregnant women not yet in labor at ≥ 39 weeks' gestation who delivered within 1 week of sonography. The AOP was compared as follows: in nulliparous women, between those who had a Cesarean section and those who delivered vaginally; and among women who delivered vaginally, between those who were nulliparous and those who were parous.

RESULTS

Included in the study were 100 nulliparous and 71 parous women. Among those who delivered vaginally (n = 161), the median AOP before onset of labor was narrower in parous than in nulliparous women (98° (interquartile range (IQR)), 90-107° vs 104° (IQR, 97-113°), P < 0.001). Among the 100 nulliparous women, (1) the median AOP before onset of labor was narrower in those who went on to deliver by Cesarean section (n = 9) than in those delivered vaginally (n = 91) (90° (IQR, 85.5-93.5°) vs 104° (IQR, 97-113°), P < 0.001); (2) an AOP ≥ 95° (derived from the receiver-operating characteristics curve) was associated with vaginal delivery in 99% of women; and (3) 89% (8/9) of women who delivered by Cesarean section had an AOP < 95°. Among the 71 parous women, only one delivered by Cesarean section and all of those with an AOP < 95° delivered vaginally.

CONCLUSION

A narrow AOP (< 95°) in non-laboring nulliparous women at term is associated with a high rate of Cesarean delivery. Parous women have a narrower AOP than do nulliparous women before the onset of labor; however, unlike in nulliparous women, a narrow AOP in parous women does not appear to be associated with Cesarean delivery and most parous women with such an angle go on to deliver vaginally.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Operative vaginal deliveries: practical aspects

Forceps, vacuum, and cesarean sections are relatively recent additions to the obstetrician's armamentarium. The art of modern obstetrics is one that mandates from obstetricians the attentive vigilance of the development of natural processes and an active intervention when such processes fall outside normally accepted standards. What constitutes the "normal process" and the "accepted standard" is subject to discussion, and international variations in obstetric practice are in part the reflection of such controversies. This article presents a practical approach to the contemporary issue of instrumental deliveries, outlining supporting evidence (when available) and the most current position of professional colleges in obstetrics and gynecology.

Prediction of delivery mode with transperineal ultrasound in women with prolonged first stage of labor

OBJECTIVE

To investigate if fetal head-perineum distance and angle of progression measured with two-dimensional (2D) and three-dimensional (3D) transperineal ultrasound could predict outcome of labor in primiparous women with prolonged first stage of labor.

METHODS

This was a prospective observational study of 110 primiparous women with singleton cephalic presentation at term diagnosed with prolonged first stage of labor. Digital assessment of fetal station was related to the ischial spine. Fetal head descent was measured with transperineal ultrasound as the shortest distance from the fetal head to the perineum, and the angle between the pubic symphysis and the fetal head. Receiver-operating characteristics (ROC) curves were constructed and 2D and 3D data acquisitions were compared. The stored 3D volumes were assessed by an examiner blinded to all other data. Vaginal delivery vs. Cesarean section was the primary outcome.

RESULTS

Cesarean section was performed in 25% of the women. Areas under the ROC curves for prediction of vaginal delivery were 81% (95% confidence interval (CI), 71-91%) (P < 0.01) and 76% (95% CI, 66-87%) (P < 0.01) for fetal head-perineum distance and angle of progression, respectively, as measured by 2D ultrasound and 66% (95% CI, 54-79%) for digital assessment of fetal station (P = 0.01). In 50% of women fetal head-perineum distance was ≤ 40 mm and 93% (95% CI, 83-97%) of them delivered vaginally vs. 18% (95% CI, 5-48%) with distance > 50 mm. In 48% of women the angle of progression was ≥ 110° and 87% (95% CI, 75-93%) of them delivered vaginally vs. 38% (95% CI, 21-57%) with angle < 100°. Results from 2D and 3D acquisitions were similar.

CONCLUSION

Fetal head-perineum distance and angle of progression measured with 2D or 3D ultrasound can predict labor outcome, with similar predictive values for the two techniques.

Clinical and sonographic parameters at 37 weeks' gestation for predicting the risk of primary Cesarean delivery in nulliparous women

OBJECTIVES

To identify the clinical and sonographic parameters at 37 weeks' gestation that predict the risk of Cesarean delivery in labor for nulliparas.

METHODS

This prospective observational study recruited nulliparas with singleton pregnancies at 37 weeks' gestation. Determination of the Bishop score, ultrasound measurement of the cervical length, and fetal biometry were performed. The clinical parameters studied were maternal age, height and weight and Bishop score. The sonographic parameters included fetal biparietal diameter, femur length, abdominal circumference (AC), estimated fetal weight (EFW), amniotic fluid index and cervical length.

RESULTS

Four hundred and fifty-three women were examined; 57 women (12.6%) underwent an emergency Cesarean delivery in labor. Logistic regression analysis identified maternal age and height and fetal AC and EFW, but not cervical length or Bishop score, as the best predictors of Cesarean delivery. Of these predictors, maternal age and height and fetal AC at 37 weeks were included in a final model for risk scoring. The model was shown to have an adequate goodness of fit (P = 0.473), and the area under the receiver-operating characteristics curve was 0.758, indicating reasonably good discrimination.

CONCLUSIONS

Maternal age and height and fetal AC and EFW at 37 weeks' gestation are the most important parameters in predicting the risk of Cesarean delivery in nulliparas; sonographic measurement of the cervical length and the Bishop score were not predictive of Cesarean delivery. A predictive model using these parameters at 37 weeks provides useful information in the decision-making process regarding the mode of delivery.