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

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

Intrapartum ultrasound in women with prolonged first stage of labor.

The first stage of labor is from the start of active labor until the cervix is fully dilatated. To assess labor progress during this stage, a clinical examination has traditionally been done. The cervical dilatation, fetal head position, and fetal head station are evaluated. Moreover, these observations can be made with an ultrasound examination. Studies have shown that traditional clinical examinations are subjective, have poor reproducibility, and are unreliable. Ultrasound examinations of the fetal head station and fetal head position in the first stage of labor might predict labor outcome and mode of delivery and can help in decision making when prolonged first stage of labor is diagnosed.

There are 4, not 7, cardinal movements in labor.

The mechanics of labor describe the forces required for fetal descent, and the movements that the fetus must perform to overcome the resistance met by the maternal bony pelvis and soft tissue. The fetus negotiates the birth canal and rotational movements are necessary for descent. Anglo-American literature lists 7 cardinal movements, namely engagement, descent, flexion, internal rotation, extension, external rotation, and expulsion. German and older English literature lists only 4 rotational movements as the cardinal movements and excludes engagement, descent, and expulsion. We would argue that descent is the main purpose of the uterine powers and cardinal movements, a description of the rotational movements the fetal head and shoulders must perform to obtain descent. Ultrasound offers a historically unique opportunity for noninvasive, dynamic studies of the mechanics of labor. The information gathered by clinical examination and ultrasound should be integrated into clinical decision making.

Ultrasound before operative vaginal delivery: why and how.

Safe management of the second stage of labor is important. Wait for spontaneous delivery, operative vaginal deliveries and second stage cesarean sections are all options when prolonged second stage occurs. The important question is which option to choose. Fetal head station and fetal head position are used to decide mode of delivery; this has traditionally been decided by performing a digital vaginal examination. Studies have shown that theses clinical examinations of both fetal head station and position are unreliable and that ultrasound might be better option. The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) published in 2018 guidelines on intrapartum ultrasound and recommends that ultrasound is performed for ascertainment of fetal head position and station before considering or performing an instrumental vaginal delivery for slow progress or arrested labor in the second stage. The determination of the fetal head position, fetal head station and the movement of the fetal head can easily be determined with the help of ultrasound and can help the clinicians in making the right decision on how to proceed when prolonged second stage of labor is diagnosed.

Fetal molding examined with transperineal ultrasound and associations with position and delivery mode.

BACKGROUND: To accommodate passage through the birth canal, the fetal skull is compressed and reshaped, a phenomenon known as molding. The fetal skull bones are separated by membranous sutures that facilitate compression and overlap, resulting in a reduced diameter. This increases the probability of a successful vaginal delivery. Fetal position, presentation, station, and attitude can be examined with ultrasound, but fetal head molding has not been previously studied with ultrasound. OBJECTIVE: This study aimed to describe ultrasound-assessed fetal head molding in a population of nulliparous women with slow progress in the second stage of labor and to study associations with fetal position and delivery mode. STUDY DESIGN: This was a secondary analysis of a population comprising 150 nulliparous women with a single fetus in cephalic presentation, with slow progress in the active second stage with pushing. Women were eligible for the study when an operative intervention was considered by the clinician. Molding was examined in stored transperineal two-dimensional and three-dimensional acquisitions and differentiated into occipitoparietal molding along the lambdoidal sutures, frontoparietal molding along the coronal sutures, and parietoparietal molding at the sagittal suture (molding in the midline). Molding could not be classified if positions were unknown, and these cases were excluded. We measured the distance from the molding to the head midline, molding step, and overlap of skull bones and looked for associations with fetal position and delivery mode. The responsible clinicians were blinded to the ultrasound findings. RESULTS: Six cases with unknown position were excluded, leaving 144 women in the study population. Fetal position was anterior in 117 cases, transverse in 12 cases, and posterior in 15 cases. Molding was observed in 79 of 144 (55%) fetuses. Molding was seen significantly more often in occiput anterior positions than in non-occiput anterior positions (69 of 117 [59%] vs 10 of 27 [37%]; P=.04). In occiput anterior positions, the molding was seen as occipitoparietal molding in 68 of 69 cases and as parietoparietal molding in 1 case with deflexed attitude. Molding was seen in 19 of 38 (50%) of occiput anterior positions ending with spontaneous delivery, 42 of 71(59%) ending with vacuum extraction, and in 7 of 8 (88%) with failed vacuum extraction (P=.13). In 4 fetuses with occiput posterior positions, parietoparietal molding was diagnosed, and successful vacuum extraction occurred in 3 cases and failed extraction in 1. Frontoparietal molding was seen in 2 transverse positions and 4 posterior positions. One delivered spontaneously; vacuum extraction failed in 3 cases and was successful in 2. Only 1 of 11 fetuses with either parietoparietal or frontoparietal molding was delivered spontaneously. CONCLUSION: The different types of molding can be classified with ultrasound. Occipitoparietal molding was commonly seen in occiput anterior positions and not significantly associated with delivery mode. Frontoparietal and parietoparietal moldings were less frequent than reported in old studies and should be studied in larger populations with mixed ethnicities.

Live born recipient of twin-twin transfusion syndrome with anomalous mitral arcade.

We present a case report of anomalous mitral arcade in a live born former recipient of twin-twin transfusion syndrome. At 33+0 week of gestation fetal ultrasound demonstrated that she had a large mitral insufficiency, decreased movement of the lateral cusp of the mitral valve and dilated left atrium. The twins were delivered by caesarean section at week 33+1 due to fetal distress. The former recipient twin developed decompensated heart failure during her first day of life and was transferred to a surgical paediatric heart centre. Her clinical condition rapidly deteriorated, and she died of congestive heart failure 3 days old. Prenatal signs of anomalous mitral arcade in a recipient of twin-twin transfusion syndrome should warrant preparation of a critically ill neonate, including parental counselling and in utero transfer to surgical paediatric heart centre. There is a surgical treatment option available for neonates, but the experience with this technique is still very limited with a high risk of morbidity and mortality.

Time to delivery based on sonographic assessment prior to forceps and vacuum.

INTRODUCTION: To compare the duration of vacuum and forceps delivery in relation to ultrasound assessment of fetal head position and station. METHODS: A prospective single-centre cohort study in nulliparous women at term with prolonged second stage of labour. Fetal head position was determined using transabdominal ultrasound and station as head-perineum distance (HPD) from transperineal ultrasound prior to an instrument. The primary outcome was duration of vacuum and forceps to vaginal delivery and was analysed as survival expressed by hazard ratio (HR). Secondary outcomes were delivery mode and immediate neonatal outcome. RESULTS: In the study population of 54 women, the primary instrument was vacuum for 36 and forceps for 18. Four women were delivered by Caesarean section. Estimated median duration for forceps deliveries was 5 min (95% CI 4.0-6.0) vs. 9 min (95% CI 7.3-10.6) for vacuum deliveries (P = 0.17; Log-rank test). The HR for vaginal delivery was 2.02 (95% CI 1.04-3.91, P = 0.038) after adjusting for HPD, maternal age and BMI. OP position had minor influence on the primary outcome (HR changed from 2.02 to 2.08). The first instrument failed in 11/31 (35.5%) where HPD > 35 mm vs. 2/21 (9.5%) where HPD ≤ 35 mm (P < 0.05). There were no cases of Apgar score <7 at 5 min or umbilical artery pH < 7.1. CONCLUSION: In prolonged second stage, delivery with forceps was achieved more quickly than by vacuum when matched for ultrasound determined head station. Irrespective of which was the primary instrument, the failure rate was greater at higher head stations.

Fetal rotation during vacuum extractions for prolonged labor: a prospective cohort study.

INTRODUCTION: The aim of the study was to investigate fetal head rotation during vacuum extraction. MATERIAL AND METHODS: We conducted a prospective cohort study from November 2013 to July 2016 in seven European hospitals. Fetal head position was determined with transabdominal or transperineal ultrasound and categorized as occiput anterior (OA), occiput transverse (OT) or occiput posterior (OP) position. Main outcome was the proportion of fetuses rotating during vacuum extraction. Secondary outcomes were conversion of delivery method, duration of vacuum extraction, umbilical artery pH <7.10 and agreement between clinical and ultrasound assessments. RESULTS: The study population comprised 165 women. During vacuum extraction 117/119 (98%) remained in OA and two fetuses rotated to OP position. Rotation from OT to OA position occurred in 14/19 (74%) and to OP position in 5/19 (26%). Rotation from OP to OA position occurred in 15/25 (60%), and 10/25 (40%) fetuses remained in OP position. Delivery information was missing in two cases. The conversion rate from vacuum extraction to cesarean section or forceps was 10% in the OA group vs. 23% in the non-OA group; p < 0.05. The estimated duration of vacuum extraction was significantly shorter in OA fetuses, 7 min vs. 10 min (log rank test p < 0.01). There was no significant difference in umbilical artery pH < 7.10 between OA and non-OA position. Cohens Kappa of agreement between clinical and ultrasound assessments was 0.42 (95% CI 0.26-0.57). CONCLUSION: Most fetuses in OP or OT positions rotated to OA position during vacuum extraction, but the proportion of failed vacuum extractions remained high.

Sonographic prediction of outcome of vacuum deliveries: a multicenter, prospective cohort study.

BACKGROUND: Safe management of the second stage of labor is of great importance. Unnecessary interventions should be avoided and correct timing of interventions should be focused. Ultrasound assessment of fetal position and station has a potential to improve the precision in diagnosing and managing prolonged or arrested labors. The decision to perform vacuum delivery is traditionally based on subjective assessment by digital vaginal examination and clinical expertise and there is currently no method of objectively quantifying the likelihood of successful delivery. Prolonged attempts at vacuum delivery are associated with neonatal morbidity and maternal trauma, especially so if the procedure is unsuccessful and a cesarean is performed. OBJECTIVE: The aim of the study was to assess if ultrasound measurements of fetal position and station can predict duration of vacuum extractions, mode of delivery, and fetal outcome in nulliparous women with prolonged second stage of labor. STUDY DESIGN: We performed a prospective cohort study in nulliparous women at term with prolonged second stage of labor in 7 European maternity units from 2013 through 2016. Fetal head position and station were determined using transabdominal and transperineal ultrasound, respectively. Our preliminary clinical experience assessing head-perineum distance prior to vacuum delivery suggested that we should set 25 mm for the power calculation, a level corresponding roughly to +2 below the ischial spines. The main outcome was duration of vacuum extraction in relation to ultrasound measured head-perineum distance with a predefined cut-off of 25 mm, and 220 women were needed to discriminate between groups using a hazard ratio of 1.5 with 80% power and alpha 5%. Secondary outcomes were delivery mode and umbilical artery cord blood samples after birth. The time interval was evaluated using survival analyses, and the outcomes of delivery were evaluated using receiver operating characteristic curves and descriptive statistics. Results were analyzed according to intention to treat. RESULTS: The study population comprised 222 women. The duration of vacuum extraction was shorter in women with head-perineum distance ≤25 mm (log rank test <0.01). The estimated median duration in women with head-perineum distance ≤25 mm was 6.0 (95% confidence interval, 5.2-6.8) minutes vs 8.0 (95% confidence interval, 7.1-8.9) minutes in women with head-perineum distance >25 mm. The head-perineum distance was associated with spontaneous delivery with area under the curve 83% (95% confidence interval, 77-89%) and associated with cesarean with area under the curve 83% (95% confidence interval, 74-92%). In women with head-perineum distance ≤35 mm, 7/181 (3.9%) were delivered by cesarean vs 9/41 (22.0%) in women with head-perineum distance >35 mm (P <.01). Ultrasound-assessed position was occiput anterior in 73%. Only 3/138 (2.2%) fetuses in occiput anterior position and head-perineum distance ≤35 mm vs 6/17 (35.3%) with nonocciput anterior position and head-perineum distance >35 mm were delivered by cesarean. Umbilical cord arterial pH <7.10 occurred in 2/144 (1.4%) women with head-perineum distance ≤35 mm compared to 8/40 (20.0%) with head-perineum distance >35 mm (P < .01). CONCLUSION: Ultrasound has the potential to predict labor outcome in women with prolonged second stage of labor. The information obtained could guide whether vacuum delivery should be attempted or if cesarean is preferable, whether senior staff should be in attendance, and if the vacuum attempt should be performed in the operating theater.