Strategies to enhance assessment of the fetal head position before instrumental delivery: a survey of obstetric practice in the United Kingdom and Ireland

Objective

To establish the current practice of obstetricians with regard to assessment of women in labour before instrumental delivery.

Study design

A national postal survey of obstetricians in consultant-led obstetric units in the United Kingdom and Ireland. Clinical assessment before instrumental delivery, factors associated with difficulty in determining the fetal head position, approaches used to enhance determination of the fetal head position, perceived accuracy rates in assessment of the fetal head position and willingness to participate in a clinical trial of ultrasound assessment of the fetal head position before instrumental delivery were explored.

Results

The response rate was 75%. The majority of obstetricians assess women clinically before instrumental delivery as recommended by guidelines. Both consultants and trainees reported the following factors as being associated with difficulty in diagnosing the fetal head position: inadequate maternal pain relief, fetal caput and clinical inexperience. Strategies used when experiencing difficulty in determining the fetal head position varied, with trainees more likely than consultants to seek a second opinion (40% vs. 5%, p < 0.0001), reassess in an operating theatre (80% vs. 68%, p = 0.048) or abandon the procedure in favour of caesarean section (14% vs. 6%, p = 0.035). One in five obstetricians reported using abdominal ultrasound to aid diagnosis, with some consultants reporting the use of ultrasound as ‘a great idea’ and others being ‘appalled’. One in eight consultants perceived that they made an incorrect diagnosis of the fetal head position at instrumental delivery in more than 10% of deliveries compared to one in four trainees.

Conclusion

The contrasting views on the role of ultrasound to enhance the assessment of the fetal head position before instrumental delivery suggest that it should be evaluated in a randomised clinical trial.     

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.     

Detection of cesarean scars by transvaginal ultrasound

OBJECTIVE: To assess the ability of transvaginal ultrasound to detect cesarean scars and their defects in the nonpregnant state. METHODS: Asymptomatic, parous volunteers underwent transvaginal ultrasound of the cervix, uterus, and adnexa. Uterine measurements, the presence or absence of a cesarean scar, and the presence of a scar defect, defined as fluid within the scar, were recorded. All subjects completed a self-report questionnaire regarding obstetric history. Sonographers and investigators were blinded to subject history. RESULTS: A total of 70 subjects were enrolled. Of these, 38 women had a prior vaginal delivery and 32 women a prior cesarean delivery. One woman with a bicornuate uterus and three cesarean deliveries was excluded from data analysis. Real-time transvaginal ultrasound proved 100% sensitive (exact 95% confidence interval [CI] 88.8, 100) and 100% specific (exact 95% CI 90.7, 100). Stored image review had a sensitivity of 87% (exact 95% CI 70.2, 96.4) and a specificity of 100% (exact 95% CI 90.7, 100). Fluid was visualized within the scars of 13 of 31 subjects (42%) with a prior cesarean delivery. All 13 were found among the 23 subjects (56%) who had labored prior to cesarean delivery. Moreover, women with cesarean scar defects had a greater number of cesarean deliveries (P <.04) than women without scar defects. CONCLUSIONS: Transvaginal ultrasound is highly accurate in detecting cesarean hysterotomy scars. Cesarean scar defect, defined by the presence of fluid within the incision site, was more common when labor preceded cesarean delivery and with multiple cesarean deliveries.     

Intrapartum sonography to determine fetal head position

Objective: To investigate the accuracy of intrapartum transvaginal digital examination in defining the position of the fetal head. Patients and methods: In 496 singleton pregnancies in labor at term, the fetal head position was determined by routine transvaginal digital examination by the attending midwife or obstetrician. Immediately before or after the clinical examination, the fetal head position was determined using transabdominal ultrasound by an appropriately trained sonographer who was not aware of the clinical findings. The digital examination was considered to be correct if the fetal head position was within 45° of the ultrasound finding. The accuracy of the digital examination was examined in relation to maternal characteristics and the progress of labor. Results: The position of the fetal head was determined by ultrasound examination in all 496 cases examined. Digital examination failed to define the fetal head position in 166 (33.5%) cases and, in 330 cases where the position was determined, the findings of the digital and sonographic examinations were in agreement in only 163 (49.4%) cases. The rate of correct identification of the fetal position by digital examination increased with cervical dilatation, from 20.5% at 3–4 cm to 44.2% at 8–10 cm, and was higher if the examination was carried out by an obstetrician than a midwife (50% versus 30%) and if there was absence rather than presence of caput (33% versus 25%). Conclusions: Routine digital examination during labor fails to identify the correct fetal position in the majority of cases.     

Influence of persistent occiput posterior position on delivery outcome.

OBJECTIVE: To evaluate the influence of intrapartum persistent occiput posterior position of the fetal head on delivery outcome and anal sphincter injury, with reference to the association with epidural analgesia. METHODS: We conducted a prospective observational study of 246 women with persistent occiput posterior position in labor during a 2-year period, compared with 13,543 contemporaneous vaginal deliveries with occiput anterior position. RESULTS: The incidence of persistent occiput posterior position was significantly greater among primiparas (2.4%) than multiparas (1.3%; P <.001; 95% confidence interval 1.4, 2.4) and was associated with significantly higher incidences of prolonged pregnancy, induction of labor, oxytocin augmentation of labor, epidural use, and prolonged labor. Only 29% of primiparas and 55% of multiparas with persistent occiput posterior position achieved spontaneous vaginal delivery, and the malposition was associated with 12% of all cesarean deliveries performed because of dystocia. Persistent occiput posterior position was also associated with a sevenfold higher incidence of anal sphincter disruption. Despite a high overall incidence of use of epidural analgesia (47% versus 3%), the institutional incidence of persistent occiput posterior position was lower than that reported 25 years ago. CONCLUSION: Persistent occiput posterior position contributed disproportionately to cesarean and instrumental delivery, with fewer than half of the occiput posterior labors ending in spontaneous delivery and the position accounting for 12% of all cesarean deliveries for dystocia. Persistent occiput posterior position leads to a sevenfold increase in the incidence of anal sphincter injury. Use of epidural analgesia was not related to the malposition.     

Establishing the accuracy and acceptability of abdominal ultrasound to define the foetal head position in the second stage of labour: a validation study

Objectives

To compare the diagnosis of the foetal head position in the second stage of labour by ultrasound scan performed by a novice sonographer and by clinical assessment, to that of an expert sonographer (gold standard); and to evaluate the acceptability of ultrasound in the second stage of labour to women and clinicians.

Study design

This is a case series. We recruited sixty women delivering in a university hospital in Dublin, Ireland. An abdominal scan was performed by a novice and an expert ultrasonographer and a clinical assessment was performed by an obstetrician or midwife. Each assessor was blinded to the findings of the others. The main outcome measures were errors in the diagnosis of the foetal head position and acceptability of abdominal ultrasound in the second stage of labour.

Results

The ultrasound findings of the novice and expert ultrasonographers were consistent in 52 (87%) cases for the foetal head position; 80% accuracy for the first ten scans performed by the novice (median time 150 s) and 90% for the last ten scans (median time 10 s). The novice made no occipito-anterior/occipito-posterior (OA/OP) errors. The clinical diagnosis of the foetal head position was incorrect in 25 (42%) cases; 8 (13%) OA/OP errors. Women and clinicians did not consider the ultrasound assessment to be intrusive.

Conclusion

An abdominal scan by a novice ultrasonographer is an accurate and acceptable method of diagnosing the foetal head position in the second stage of labour and may have a role to play in assessment prior to instrumental delivery.     

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.     

再谈头位阴道助产术

头先露的阴道助产术包括产钳助产术和胎头负压吸引术。在第二产程中判断胎头位置及胎方位是阴道助产成功的关键。胎头最低位置于坐骨棘2 cm以下,胎方位为枕前位者,助产风险相对小。产科医生要严格把握阴道助产的手术指征,并与患者充分沟通。临床医生的判断能力,培训经历以及临床经验是助产成功的重要因素。     

Transabdominal ultrasound assessment of the fetal head and the accuracy of vacuum cup application.

OBJECTIVE: To investigate whether the accuracy of vacuum cup placement can be improved by intrapartum ultrasound assessment of the fetal head position during the second stage of labor prior to vacuum extraction for prolonged second stage. METHODS: 50 women undergoing vacuum extraction for prolonged second stage were randomly allocated to either digital examination (n=25) or digital examination together with transabdominal intrapartum ultrasound (n=25) prior to vacuum extraction by the attending obstetrician. The distance between the centre of the chignon and the flexion point was then measured by a midwife immediately after delivery. The flexion point was defined as 6 cm posterior to the anterior fontanelle or 3 cm anterior to the posterior fontanelle. RESULTS: There were no statistically significant differences in the demographic data, duration of labor, incidence of induction/augmentation, and intrapartum complications between the two groups. The mean distance between the centre of the chignon and the flexion point was 2.1+/-1.3 cm in the group with digital examination and ultrasound assessment and 2.8+/-1.0 cm in the group with digital examination alone. The difference in the mean distance between the two groups was statistically significant (p=0.039). CONCLUSION: Intrapartum transabdominal ultrasound assessment of the fetal head position during the second stage of labor improves the accuracy of vacuum cup placement during vacuum extraction for prolonged second stage.     

Detection of small-for-gestational-age fetuses by ultrasound screening in a high risk population: a randomized controlled study.

OBJECTIVE: To assess the value of fetal weight estimation during routine third trimester ultrasound examinations for the identification of small-for-gestational-age (SGA) fetuses, to promote active pregnancy management and so reduce perinatal morbidity. DESIGN: A prospective controlled randomized study. SETTING: Outpatient clinic at the Department of Obstetrics, Herlev University Hospital, Denmark. SUBJECTS: One thousand pregnant women considered at risk were selected consecutively from April 1985 to September 1987 and randomized to either a revealed-results group or a withheld-results group. INTERVENTION: All the women had an early ultrasound examination for estimation of gestational age. Both groups had routine ultrasound estimates of fetal weight after 28 weeks and then every third week until delivery. The results were available for clinical use only in the revealed group. MAIN OUTCOME MEASURES: Number of interventions during pregnancy (admission to hospital, elective delivery), emergency intervention during labour, and fetal outcome. RESULTS: Revealing the results of ultrasound estimates of fetal weight for gestational age during the third trimester resulted in statistically significantly increased diagnosis of SGA fetuses, of elective deliveries based on this diagnosis, and of healthy preterm babies admitted to the neonatal care unit, but no detectable overall improvement in weight for gestational age at birth, or in neonatal morbidity or mortality. CONCLUSION: This method of screening improved the diagnosis of SGA fetuses, but this was not followed by improved fetal outcome.     

Le suivi échographique de la deuxième partie du travail

In the second stage of labor, fetal head rotation and fetal head position are determinant for the management of labor to attempt a vaginal delivery or a cesarean section. However, digital examination is highly subjective. Nowadays, delivery rooms are often equipped with compact and high performance ultrasound systems. The clinical examination can be easily completed by quantified and reproducible methods. Transabdominal ultrasonography is a well-known and efficient way to determine the fetal head position. Nevertheless, ultrasound approach to assess fetal head descent is less widespread. We can use translabial or transperineal way to evaluate fetal head position. We describe precisely two different types of methods: the linear methods (3 different types) and the angles of progression (4 different types of measurement). Among all those methods, the main pelvic landmarks are the symphysis pubis and the fetal skull. The angle of progression appears promising but the assessment was restricted to occipitoanterior fetal position cases. In the coming years, ultrasound will likely play a greater role in the management of labor.     

Failed instrumental delivery: Ramathibodi Hospital, 1980-1988.

All cases (70) of failed instrumental deliveries which occurred between 1980 and 1988 at Ramathibodi Hospital, Bangkok, Thailand were critically reviewed. The incidence of failure was 0.5%, and failure occurred more often in primigravidae. Failure to appreciate the true level of the fetal head and too early intervention accounted for failure in 50% of the cases. Failed instrumental delivery can be minimized if the prerequisites for the procedure are strictly adhered to.     

Usefulness of ultrasound in the delivery room

The use of diagnostic ultrasound and the diffusion of the technique improved the obstetric treatment and the usefulness of ultrasound increases in the delivery room for maternal and fetal care and as method of diagnosis of some obstetric complications. The knowledge of intrapartum ultrasound imaging can be considered useful for the obstetric team, since there is evidence that ultrasound can improve the obstetric management. The mean indications are described: fetal biometry and estimated fetal weight, amniotic fluid volume, fetal situation and presentation, placental localization and anatomy, assessment of size and location of uterine leiomyomas, fetal cardiac activity, evaluation of umbilical cord and fetal cardinal movements intrapartum. Besides, the use of ultrasound is reported in obstetric and postpartum complications. Actually ultrasonography, as a non-invasive, safety and low-cost technique, offers a diagnostic method in particular conditions during labour, delivery and postpartum.     

Occipito-posterior fetal head position, maternal and neonatal outcome

The purpose of this review is to summarize the available evidence on occipito-posterior fetal head position and maternal and neonatal outcome. The occipito-posterior fetal head position is the most common malposition, but there are not so many data about it in literature. Its incidence is ranging from 1.8% by Fitzpatrick, to 4.6% and 5.5% by Yancey and Sizer, to 6% by Ponkey. Only two trials studied the occipito-posterior associated factors. There are lower incidence of premature rupture of membrane, arterial hypertension pregnancy-induced, induced labour, increased of episiotomy, instrumental delivery and a decreased of vaginal birth without a difference in neonatal Apgar, and with a neonatal bigger weight. The occipito-posterior fetal head position persistence compared to anterior position, has a statistically significant association with low maternal stature, previous cesarean section, longer first and second stage of labour, oxytocin augmentation, epidural analgesia, instrumental vaginal delivery, chorion-amniositis, vaginal perineal injures, loss of blood and post partum infections. A highest incidence of occipito-posterior fetal head position may depend by nulliparity, malnutrition with pelvic deformity, pelvic immaturity in the teenager and anterior placenta. Epidural analgesia is a risk factor for fetal head malposition. The majority of occipito-posterior fetal head positions is not due to a malrotation, but to a persistence in this position of the fetal head. In fact, this persistence leads to a failure of the fetal head rotation. The prolonged second stage is often the result of occipito-posterior fetal head position and instrumental delivery is required. The traditional vaginal examination is not useful for the determination of fetal head position, so and instrumental method is needed, such as ultrasound, for a correct evaluation of fetal head position, particularly if a vaginal instrumental delivery is necessary. This is recommended by the Canadian Society of Obstetrics and Gynecology. The evaluation of fetal head position is important in the prediction of labour induction.     

Failed individual and sequential instrumental vaginal delivery: contributing risk factors and maternal-neonatal complications

BACKGROUND: To identify the risk factors for failed instrumental vaginal delivery, and to compare maternal and neonatal morbidity associated with failed individual and sequential instruments used. DESIGN: A retrospective case-control study. METHODS: From January 1995 to June 2001, there were 39 508 live births at >37 weeks' gestation of which 2628 (6.7%) instrumental vaginal deliveries were performed, 1723 (4.4%) were vacuum extractions and 905 (2.3%) were forceps. A total of 155/2628 (5.9%) patients who had failed instrumental delivery were matched with 204 patients who had successful instrumental delivery. The patients were divided into five groups. Group I (n = 129) had failed vacuum extraction, group II (n = 13) failed forceps, group III (n = 13) failed both (i.e. failed attempt at both instruments sequentially), group IV (n = 138) had successful vacuum extraction and group V (n = 66) successful forceps. RESULTS: The failure rate for vacuum extractions 129/1723 (7.5%) was significantly higher than that for forceps 13/905 (1.4%) [odds ratio (OR) = 5.6, 95% CI 3-10.3]. There were no significant differences in all maternal complications (25.5% vs. 26.6%) between vacuum (groups I and IV) and forceps (groups II and V) assisted deliveries. There were more maternal complications in group III (46.2%) than in groups I (35.7%), II (23.1%) and V (27.3%) that did not reach statistical significance but were significantly higher than in group IV (15.9%, OR = 4.5, 95% CI 1.2-16.9). There was a significantly higher rate of all fetal complications in group III [11/13 (84.6%)] than in groups I [69/129 (53.5%)], II [7/13 (53.8%)], IV [35/138 (25.4%)] and V [22/66 (33.3%)] (OR = 4.8, 95% CI 0.9-19.9). CONCLUSIONS: Applying the instrument at < or =0 fetal station, nulliparous women, history of previous cesarean section and fetal head other than occipitoanterior position were risk factors for failed instrumental delivery. Sequential use of instrumental delivery carries a significantly higher neonatal morbidity than when a single instrument is used.     

Asynclitism: a literature review of an often forgotten clinical condition

Asynclitism is defined as the “oblique malpresentation of the fetal head in labor”. Asynclitism is a clinical diagnosis that may be difficult to make; it may be found during vaginal examination. It is significant because it may cause failure of progress operative or cesarean delivery. We reviewed all literature for asynclitism by performing an extensive electronic search of studies from 1959 to 2013. All studies were first reviewed by a single author and discussed with co-authors. The following studies were identified: 8 book chapters, 14 studies on asynclitism alone and 10 papers on both fetal occiput posterior position and asynclitism. The fetal head in a laboring patient may be associated with some degree of asynclitism; this is seen as usual way of the fetal head to adjust to maternal pelvic diameters. However, marked asynclitism is often detected in presence of a co-existing fetal head malposition, especially the transverse and occipital posterior positions. Digital diagnosis of asynclitism is enhanced by intrapartum ultrasound with transabdominal or transperineal approach. The accurate diagnosis of asynclitism, in an objective way, may provide a better assessment of the fetal head position that will help in the correct application of vacuum and forceps, allowing the prevention of unnecessary cesarean deliveries.     

Vaginal ultrasound as an adjunct to cervical digital examination in women at risk of early delivery

AIM: To study the utility of transvaginal ultrasound (TVU) in women at high risk of preterm delivery. METHODS: Women who were scheduled for frequent digital examinations of the cervix from 16 to 26 weeks of gestation had TVU determinations of cervical length before their clinical examinations. Clinicians were blinded to the TVU results. Therefore, clinical decision-making was independent of the unreported TVU data. The plan was to relate the ultrasound characterization of the cervix to the study's primary endpoint, the need for hospitalization prior to 26 weeks of gestation for: preterm premature rupture of membranes, preterm labor, cerclage placement, or delivery. RESULTS: Seventeen subjects completed the study. All 3 who met the primary endpoint had ultrasound cervical lengths <20 mm on earlier prenatal visits, when digital examinations of the cervix did not detect problems. A 4th woman had ultrasound lengths <20 mm (she delivered at 27(6)/(7) weeks). CONCLUSION: TVU determination of cervical length provides an earlier warning of cervical shortening than does digital examination.     

Prediction of successful induction of labor at term: role of clinical history, digital examination, ultrasound assessment of the cervix, and fetal fibronectin assay

OBJECTIVE: The purpose of this study was to evaluate whether biochemical (fetal fibronectin assay) or biophysical (cervical assessment by transvaginal ultrasound) tests may have more value than digital examination in predicting successful induction of labor at term. STUDY DESIGN: The study enrolled prospectively 134 women undergoing labor induction at term caused by several obstetric conditions. All participants submitted to digital examination, fetal fibronectin assay, and transvaginal ultrasound for measurement of the cervical length and detection of funneling. The performance of each test in predicting delivery within 24 hours of labor induction was evaluated. Cox multiple regression analysis was performed to identify, among clinical and laboratory tests, which variables were independently associated with the duration of the latent phase and with the total duration of induced labor. RESULTS: The likelihood ratios for positive results (predicting that delivery would occur within 24 hours) were 6.61 (95% CI, 1.7-25.8) for a positive obstetric history (previous vaginal delivery), 2.61 (95% CI, 1.6-4.3) for a "favorable" digital examination, 1.41 (95% CI, 0.9-2.2) for a positive fetal fibronectin test, 1.61 (95% CI, 0.9-3.0) for cervical length, and 2.20 (95% CI, 1.1-4.4) for the presence of funneling at transvaginal ultrasound. The likelihood ratios for negative results were 1.81 (1.3-2.5) for obstetric history, 4.34 (2.5-7.7) for digital examination, 1.41 (0.9-2.1) for fetal fibronectin, 1.29 (1.0-1.7) for cervical length, and 1.48 (1.1-2.0) for funneling. On multiple regression, the only variables independently associated with the duration of the latent phase and with the total duration of induced labor were obstetric history and digital examination. CONCLUSION: Only obstetric history and digital examination predicted accurately vaginal delivery within 24 hours and were independently associated with labor duration. Fetal fibronectin and ultrasound measurements failed to predict accurately the outcome of induced labor.     

A pilot study using intra-partum ultrasound to aid in the definition of the position of the fetal head before operative delivery.

We conducted a pilot study on 60 women in the second stage of labour using trans-abdominal ultrasound to assess fetal position prior to obstetric intervention. Digital examination failed to assess the correct fetal position in 16 (26%) of the cases. Ultrasound helped in determining fetal position in 57 (95%) of the cases. In 40 cases (66%), the obstetrician involved found the use of ultrasound to determine fetal position aided in the management of the second stage. All obstetricians involved in the study rated the ease of use of ultrasound in the second stage highly (>8/10) on a visual analogue scale. We have highlighted the role, ease of use and feasibility of intra-partum ultrasound to determine fetal position in the second stage of labour before an obstetric intervention, by the obstetrician in a District General Hospital setting.     

Vaginal versus ultrasound examination of fetal occiput position during the second stage of labor

OBJECTIVE: The purpose of this study was to determine whether ultrasonography is more accurate than vaginal examination in the determination of fetal occiput position in the second stage of labor. STUDY DESIGN: Eighty-eight patients in the second stage of labor were evaluated by vaginal examination and by combined transabdominal and transperineal ultrasound examination to determine occiput position. These predictions of position were compared with the actual delivery position at vaginal delivery after spontaneous restitution or at cesarean delivery. Different examiners performed the vaginal examinations and the ultrasound examinations. Each examiner was blinded to the determination of the other examiner. RESULTS: Vaginal examination determined fetal occiput position correctly 71.6% of the time; ultrasound examination determined fetal occiput position correctly 92.0% of the time (P=.018). CONCLUSION: Ultrasound examination is more accurate than vaginal examination in the diagnosis of fetal occiput position in the second stage of labor.