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.

Sonographic prediction of vaginal delivery in prolonged labor: a two-center study

OBJECTIVE

To investigate whether head-perineum distance (HPD) measured by transperineal ultrasound is predictive of vaginal delivery and time remaining in labor in nulliparous women with prolonged first stage of labor and to compare the predictive value with that of angle of progression (AoP).

METHODS

This was a prospective observational study at Stavanger University Hospital, Norway and Addenbrooke's Hospital, Cambridge, UK from January 2012 to April 2013, of nulliparous women with singleton pregnancies with cephalic presentation at term with prolonged first stage of labor. We used transperineal ultrasound to measure HPD (shortest distance between the outer bony limit of the fetal skull and the perineum) and AoP (angle between a line through the long axis of the symphysis and the tangent to the fetal head) and transabdominal ultrasound to classify fetal head position. The main outcomes were vaginal delivery and time remaining in labor.

RESULTS

Of 150 women enrolled, 39 underwent delivery by Cesarean section. The area under the receiver-operating characteristics curve for the prediction of vaginal delivery was 81% (95% CI, 73-89%) using HPD as the test variable and 72% (95% CI, 63-82%) using AoP. HPD was ≤ 40 mm in 84 (56%) women, of whom 77 (92%; 95% CI, 84-96%) delivered vaginally. HPD was > 40 mm in the other 66 (44%) women, of whom 34 (52%; 95% CI, 40-63%) delivered vaginally. AoP was ≥ 110° in 84 of the 145 (58%) in whom this was available and, of these, 74 (88%; 95% CI, 79-93%) delivered vaginally. AoP was < 110° in the other 61 (42%) women, of whom 35 (57%; 95% CI, 45-69%) delivered vaginally. Multivariable logistic regression analysis showed that HPD ≤ 40 mm (odds ratio (OR), 4.92; 95% CI, 1.54-15.80), AoP ≥ 110° (OR, 3.11; 95% CI, 1.01-9.56), non-occiput posterior position (OR, 3.36; 95% CI, 1.24-9.12) and spontaneous onset of labor (OR, 4.44; 95% CI, 1.42-13.89) were independent predictors for vaginal delivery. Both ultrasound methods were predictive for the time remaining in labor.

CONCLUSION

Transperineal ultrasound measurement of HPD and AoP provide important information about the likelihood of vaginal delivery and the time remaining in labor in nulliparous women with prolonged labor.

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.

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.

Estimation of fetal weight in pregnancies past term

INTRODUCTION

The aim of the study was to investigate the accuracy of estimating fetal weight with ultrasound in pregnancies past term, using the eSnurra algorithm.

MATERIAL AND METHODS

In all, 419 women with pregnancy length of 290 days, attending a specialist consultation at Stavanger University Hospital, Norway, were included in a prospective observational study. Fetal weight was estimated using biparietal diameter (BPD) and abdominal circumference (AC). The algorithm implemented in an electronic calculation (eSnurra) was used to compute estimated fetal weight (EFW). Results were compared with birthweight (BW).

RESULTS

The mean interval between the ultrasound examination and birth was 2 days (SD 1.4). The median difference between BW and EFW was -6 g (CI -40 to +25 g) and the median percentage error was -0.1% (95% CI -1.0 to 0.6%). The median absolute difference was 190 g (95% CI 170-207 g). The BW was within 10% of EFW in 83% (95% CI 79-87%) of cases and within 15% of EFW in 94% (95% CI 92-96%) of cases. Limits of agreement (95%) were from -553 g to +556 g. Using 5% false-positive rates, the sensitivity in detecting macrosomic and small for gestational age fetuses was 54% (95% CI 35-72%) and 49% (95% CI 35-63%), respectively.

CONCLUSION

The accuracy of fetal weight estimation was good. Clinicians should be aware of limitations related to prediction at the upper and lower end, and the importance of choosing appropriate cut-off levels.

A more liberal approach towards induction of labour in prolonged pregnancy does not result in an adverse labour outcome

INTRODUCTION

Discussions among Norwegian obstetricians on how to handle prolonged pregnancies have been ongoing throughout the past decade. In 2011, the Norwegian Directorate of Health recommended a specialist care consultation one week after the estimated date of delivery, implying prompt induction of labour in women at risk. The aim of this study was to compare an expectant management with a more liberal approach towards induction of labour, and to assess how the women responded to these recommendations.

MATERIAL AND METHODS

A quality assurance study was performed at Stavanger University Hospital in women with a pregnancy length ≥ 290 days. A total of 480 women who delivered prior to the introduction of the new guidelines (control period) were compared with 493 women treated according to the new recommendations (study period).

RESULTS

A total of 421/493 (85%) women in the study period attended the consultation on day 290. Of these, 61% were recommended early induction of labour (within 24 hours) because their pregnancy was a risk pregnancy. Four percent of the women with risk factors awaited spontaneous labour until day 294, versus 20% of low-risk women. When comparing the two periods, we observed an increase in the frequency of induced labour from 38% to 65%, an insignificant elevation of Caesarean section rates from 11.5% to 13.8%, and no significant increase in other interventions or in adverse newborn outcomes.

CONCLUSION

A more liberal approach towards induction of labour one week after the estimated date of delivery did not lead to an adverse labour outcome.

FUNDING

none.

TRIAL REGISTRATION

not relevant.