The trouble with vacuum extraction

The impact of selective episiotomy on maternal short-term morbidity: a retrospective study

BACKGROUND

The aim is to investigate the risk of short-term maternal morbidity caused by the selective clinical use of episiotomy (rate < 0.02), and to compare the risk of severe perineal tears with the statewide risk.

METHODS

In this retrospective cohort study, we investigated the effect of selective episiotomy on the risk of severe perineal tears and blood loss in singleton term deliveries, using propensity scores with inverse probability weighting.

RESULTS

This study included 10992 women who delivered vaginally between 2008-2018. Episiotomy was performed in 171 patients (1.55%), three of whom (1.75%) experienced severe perineal tears compared to 156 (1.44%) in the control cohort. The adjusted odds ratio of severe perineal tears was 2.06 (95% confidence interval [CI]: 0.51, 8.19 with 0.3 p value). Multivariate linear regression showed that episiotomy increased blood loss by 96.3 ml (95% CI: 6.4, 186.2 with 0.03 p value). Episiotomy was performed in 23% (95% CI: 0.228, 0.23) of vaginal deliveries in the state of Hessen, with a risk of severe perineal tears of 0.0143 (95% CI: 0.0139, 0.0147) compared to 0.0145 (95% CI: 0.0123, 0.0168) in our entire cohort.

CONCLUSIONS

Selective use of episiotomy does not increase the risk of higher-grade perineal tears. However, it may be associated with maternal morbidity in terms of increased blood loss.

Proposal of Manufacturing Method for New Passive Elastic Joint and Prototype of Human Phantom

Fabricating a soft robot using conventional molding methods is difficult and time-consuming. Moreover, the types of materials used in the process are limited, and the elasticity cannot be changed incrementally. In this paper, we explain the detailed process of manufacturing molds for silicone joints. We construct a prototype molded silicone joint. We measure the elastic modulus of this joint and confirm that the elastic modulus and anisotropy change depending on the density, size, and arrangement of the surface grooves in the mold. We also develop a prototype human phantom using the proposed joint. We aim to contribute to the medical field by applying new techniques made possible by soft robotics.

Antepartum ultrasound prediction of failed vacuum-assisted operative delivery: a prospective cohort study

BACKGROUND

Failed vacuum-assisted delivery (VD) is associated with increased risk of maternal perineal trauma and neonatal morbidity. Knowledge of the risk factors related to failed VD is essential in the clinical decision-making.

OBJECTIVE

To elucidate the strength of association and the predictive accuracy of different ante-partum ultrasound parameters in predicting the risk of failed VD prior to the onset of Labor and to test the diagnostic performance of a multiparametric model including pregnancy and Labor characteristics, ante and intra-partum ultrasound in anticipating failed VD.

STUDY DESIGN

Prospective study of consecutive singleton pregnancies complicated by VD undergoing a dedicated ultrasound assessment at 36-38 weeks of gestation. Head circumference (HC), estimated fetal weight (EFW) and subpubic angle and (SPA) were recorded before the onset of Labor. At the time of the VD, occiput position, head perineum distance (HPD) and angle of progression (AOP) were also recorded. Multivariate logistic regression and area under the curve (AUC) analyses were used to explore the strength of association and test the diagnostic accuracy of different maternal, Labor and ultrasound characteristics in predicting g failed VD.

RESULTS

Four hundred eight pregnancies with successful and 26 with failed VD were included in the analysis. Fetuses experiencing failed VD had a larger HC (1.21 versus 1.07 MoM; p = .0001), a higher EFW z-value (0.56 versus 0.33 z values; p = .002) and a narrower SPA (114 versus 122 p = .0001) compared to those having a successful VD. At multivariable logistic regression analysis, maternal height (aOR 0.89 95% CI 0.76-0.98), nulliparity (aOR: 1.14 95% CI 1.06-1.36), HC MoM (aOR: 1.24 95% CI 1.13-1.55) and SPA angle (aOR: 0.82 95% CI 0.67-0.95), but not EFW (p = .08) were independently associated with failed VD. When intrapartum ultrasound variables were added to the multivariate model, fetal occipital position (aOR: 1.45 95th CI 1.11-1.99) and HPD (aOR: 0.77 95th CI 0.44-0.96) were independently associated with failed VD. A multiparametric model integrating pregnancy and Labor characteristics and ante-partum ultrasound variables had an AUC of 0.837 (95% CI 0.797-0.876) for the prediction of failed VE. The addition of intra-partum ultrasound variables to the prediction model, improved the accuracy for failed VD provided by maternal and antepartum ultrasound characteristics with an AUC of 0.913 (0.888-0.937).

CONCLUSION

Antepartum prediction of failed VD is feasible. HC, SPA but not EFW are independently associated and predictive of failed VD. Adding these variables to a multiparametric model including maternal and intrapartum ultrasound parameters improves the diagnostic accuracy for failed VD.

"Strategies to increase the accuracy and safety of OVD" (Clinical assessment skills and role of ultrasound, simulation training and new technologies to enhance instrument application)

Operative vaginal delivery (OVD) is commonly performed in the UK and Ireland. With skillful practice, the risks to mothers and babies are low. Caesarean section at full dilatation, particularly after failed OVD, can be more hazardous for mothers and babies. It is important to maintain and develop skills in OVD in order to provide it as a safe delivery option when the benefits outweigh the risks. As ultrasound machines have become more readily available on the labour ward, ultrasound assessment has been used to help clinicians diagnose the fetal head position and station, and also to try predict the success of the delivery. Simulation training has successfully been used in the setting of obstetric emergencies and is being developed to teach both technical and communication skills in OVD in order to improve maternal and neonatal outcomes. In this chapter we will discuss strategies to improve the accuracy and safety of OVD in more details.

Vacuum extraction failure is associated with a large head circumference

Objective: To determine whether large head circumference increases the risk of vacuum extraction failure. Study design: This EMR-based study included all attempted vacuum extractions performed in a tertiary center between January 2010 and June 2015. All term singleton live births were eligible. Cases were divided into four groups: head circumference ≥90th percentile both with birth weight ≥90th percentile and <90th percentile and fetal head circumference <90th percentile with birth weight ≥90th and <90th percentile. Risk of failed vacuum extraction was compared among these groups. Other neonatal and maternal parameters were also evaluated as potential risk factors. Multinomial multivariable regression provided adjusted odds ratio for vacuum extraction failure while controlling for potential confounders. Results: During the study period, 48,007 deliveries met inclusion criteria, of which 3835 had an attempt at vacuum extraction. We identified 215 (5.6%) cases of vacuum extraction failure. The adjusted odds ratios (aOR) for vacuum extraction failure in cases of large fetal head circumference was 2.31 (95%CI, 1.7-3.15, p < .001). Primiparity, prolonged second stage and occipito-posterior presentation were also found to be significant risk factors for failed vacuum extraction. Comments: In this study, we found that large head circumference was associated with vacuum extraction failure rather than high birth weight.

Vacuum extraction vaginal delivery: current trend and safety

Operative vaginal birth retains an important role in current obstetric practice. However, there is an increasing trend in the rate of cesarean section in Korea. Surgical delivery is more advantageous than cesarean section, but the rate of operative vaginal delivery is decreasing for various reasons. Furthermore, there is no unified technique for vacuum extraction delivery. In this context, this review was performed to provide details of the necessary conditions, techniques, benefits, and risks of operative vaginal delivery. Future research should focus on overcoming the limitations of operative vaginal delivery.

Preterm birth by vacuum extraction and neonatal outcome: a population-based cohort study

BACKGROUND

Very few studies have investigated the neonatal outcomes after vacuum extraction delivery (VE) in the preterm period and the results of these studies are inconclusive. The objective of this study was to describe the use of VE for preterm delivery in Sweden and to compare rates of neonatal complications after preterm delivery by VE to those found after cesarean section during labor (CS) or unassisted vaginal delivery (VD).

METHODS

Data was obtained from Swedish national registers. In a population-based cohort from 1999 to 2010, all live-born, singleton preterm infants in a non-breech presentation at birth, born after onset of labor (either spontaneously, by induction, or by rupture of membranes) by VD, CS, or VE were included, leaving a study population of 40,764 infants. Logistic regression analyses were used to calculate adjusted odds ratios (AOR), using unassisted vaginal delivery as reference group.

RESULTS

VE was used in 5.7% of the preterm deliveries, with lower rates in earlier gestations. Overall, intracranial hemorrhage (ICH) occurred in 1.51%, extracranial hemorrhage (ECH) in 0.64%, and brachial plexus injury in 0.13% of infants. Infants delivered by VE had higher risks for ICH (AOR = 1.84 (95% CI: 1.09-3.12)), ECH (AOR = 4.48 (95% CI: 2.84-7.07)) and brachial plexus injury (AOR = 6.21 (95% CI: 2.22-17.4)), while infants delivered by CS during labor had no increased risk for these complications, as compared to VD.

CONCLUSION

While rates of neonatal complications after VE are generally low, higher odds ratios for intra- and extracranial hemorrhages and brachial plexus injuries after VE, compared with other modes of delivery, support a continued cautious use of VE for preterm delivery.

Is it Time to Rejuvenate the Forceps?

The obstetric forceps was designed to assist extraction of the foetal head and thereby accomplish delivery of the foetus in the second stage of labour. More than 700 types of obstetric forceps have been described. An understanding of the anatomy of the birth canal and the foetal head is a prerequisite to becoming a skilled and safe user of forceps. Operative vaginal delivery rates have remained stable at between 10 and 13 %. The last few decades has seen a rise in caesarean section, along with the introduction and safe use of the vacuum extractor. This has resulted in a decline both in the use of the obstetric forceps as well as in the training for the same. The forceps is less likely to fail when used as the primary instrument thereby reducing the need for the sequential use of two instruments which increase the morbidity of the neonate. Perineal trauma is more likely to occur with the use of the forceps but the evidence is that the maternal concern is less when compared to the ventouse. Simulation training is an important part of obstetric training. Application of forceps blades in the simulation setting can improve the skill level of obstetricians. The use of the forceps should not be decreasing and more senior involvement in training is necessary so that juniors develop the proper skills to perform forceps delivery in a competent and safe manner. It is vital that the art of the forceps is not lost to future generations of obstetricians and the women they care for.

Rapid versus stepwise negative pressure application for vacuum extraction assisted vaginal delivery

BACKGROUND

Vacuum extraction is a common technique of assisted vaginal delivery. Traditionally, it has been recommended that the pressure is increased slowly in a stepwise procedure; some have advocated rapid increases in pressure.

OBJECTIVES

To assess the efficacy and safety of rapid versus stepwise negative pressure application for assisted vaginal delivery by vacuum extraction.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (4 April 2012).

SELECTION CRITERIA

Randomized controlled trials and quasi-randomized controlled trials of rapid (within two minutes) versus stepwise (as defined by trialists) increases in negative pressure application for vacuum extraction assisted vaginal delivery.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and trial quality. The same two review authors extracted data. We entered data into Review Manager software and checked for accuracy. Data extraction and 'Risk of bias' assessment of the contact person's own study were also carried out by three independent assessors who were not involved in the new study.

MAIN RESULTS

We included two trials involving 754 participants.One new trial of 660 participants showed the same success rate of vacuum procedure of 98.2% by both methods (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.98 to 1.02).The two included trials showed significant reductions in the time between applying the vacuum cup and delivery, (one trial (74 women): mean difference (MD) -6.10 minutes, 95% CI -8.83 to -3.37 and the other trial (660 women): with median difference -4.4 minutes, 95% CI -4.8 to -4.0). The two included trials showed no significant difference in detachment rate (RR 0.85, 95% CI 0.38 to 1.86, 2 studies, 754 women), no significant difference in Apgar score below seven at one minute (RR 1.04, 95% CI 0.51 to 2.09) and five minutes (RR 1.00, 95% CI 0.29 to 3.42), no significant differences in scalp abrasions or lacerations, cephalhematoma, subgaleal hemorrhage and hyperbilirubinemia. There were no significant differences between the two methods in all secondary outcomes.

AUTHORS' CONCLUSIONS

The rapid negative pressure application for vacuum assisted vaginal birth reduces duration of the procedure whilst there is no evidence of differences in maternal and neonatal outcomes. Rapid method of negative application should be recommended for vacuum extraction assisted vaginal delivery.

Rapid versus stepwise application of negative pressure in vacuum extraction-assisted vaginal delivery: a multicentre randomised controlled non-inferiority trial

OBJECTIVE

To evaluate whether the application of rapid negative pressure for vacuum-assisted delivery is as effective and safe as the stepwise method.

DESIGN

Randomised controlled trial.

SETTING

Six centres, including university, secondary and tertiary hospitals, in Thailand.

SAMPLE

In total, 662 women were randomised to rapid and stepwise groups, with 331 women in each group.

METHODS

Vacuum extraction was performed by applying a metal cup (Malmstrom) connected to an electric pump to the fetal head. The stepwise method consisted of four incremental steps of 0.2 kg/cm² every 2 minutes to obtain a final negative pressure of 0.8 kg/cm². In the rapid method the negative pressure of 0.8 kg/cm² was applied in one step in < 2 minutes.

MAIN OUTCOME MEASURES

Success rate of vacuum extraction, vacuum cup detachment rate, duration of vacuum extraction, and maternal and neonatal complications.

RESULTS

There were no significant differences in detachment rates (RD 0.3%, 95% CI -3.1 to 2.4). The overall success rates were identical, at 98.2%. There were significant reductions in the time between applying the vacuum cup and attaining maximum negative pressure (MD -4.6 minutes; 95% CI -4.4 to -4.8 minutes), and in the time between applying the cup and delivery (MD -4.4 minutes; 95% CI -4.8 to -4.0 minutes). There was a significantly higher rate of perineal suture in the rapid method group (RD 4.5%; 95% CI 1.1-8.2). There were no significant differences in maternal and fetal morbidities.

CONCLUSIONS

Rapid negative pressure vacuum extraction could be performed as effectively and safely as the stepwise method, in a shorter period of time.

Rapid versus stepwise negative pressure application for vacuum extraction assisted vaginal delivery

BACKGROUND

Vacuum extraction is a common technique of assisted vaginal delivery. Traditionally, it has been recommended that the pressure is increased slowly in a stepwise procedure; some have advocated rapid increases in pressure.

OBJECTIVES

To assess the efficacy and safety of rapid versus stepwise negative pressure application for assisted vaginal delivery by vacuum extraction.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (March 2008).

SELECTION CRITERIA

Randomized controlled trials and quasi-randomized controlled trials of rapid compared with stepwise increase in negative pressure application of vacuum extraction.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

One trial of 94 women was included. Duration of vacuum procedure was reduced in rapid application group (mean difference -6.10 minutes, 95% confidence interval -8.83 to -3.37). There were no significant differences in detachment rate, degree of perineal tears, Apgar score less than seven at one and five minutes, umbilical venous pH less than 7.2, scalp laceration greater than a quarter, cephalhematoma and number of tractions.

AUTHORS' CONCLUSIONS

The rapid negative pressure application for vacuum assisted vaginal birth reduces the duration of the procedure whilst there is no evidence of differences in maternal and neonatal outcome. Due to a small number of participants in the single included trial, the evidence is limited and either policy may be employed until further controlled trials provide conclusive evidence of benefit from one or other method.

Can formal education and training improve the outcome of instrumental delivery?

OBJECTIVE(S)

The primary objective was to examine the effect of formal education and training on instrumental delivery with respect to its success rate and associated neonatal and maternal morbidity. The secondary objective was to determine factors that could influence the success rate of instrumental delivery.

STUDY DESIGN

Prospective case-control study with historical controls set in a teaching hospital in Sheffield. The prospective group included all women who had instrumental deliveries between 1 November 1999 and 29 February 2000. The control group included all women who delivered between 1 February 1997 and 1 February 1998. An educational package involving formal postgraduate training and self-directed learning were introduced in the time period between the prospective and the control groups. Medical notes were reviewed in the historical controls. For both the control and prospective groups, the following patient characteristics were recorded: maternal age, parity, whether or not onset of labour was induced, use of oxytocin in the second stage of labour, delay in the second stage, operator grade, vaginal findings at delivery and the use of epidural analgesia.

RESULTS

The overall failure rate was not different in the prospective group (16%) compared with the control group (18.5%). However, the introduction of an educational package was associated with significant decrease in maternal morbidity associated with cervical, severe labial and high vaginal tears (Odds Ratio (OR) 0.29, CI 0.09-0.97) and neonatal morbidity associated with admission to SCBU (OR 0.72, CI 0.02-0.60), severe neonatal scalp injury (OR 0.14, CI 0.02-0.98) and facial injuries (OR 0.02, CI 0.01-0.04). The factors identified to affect the success of instrumental deliveries were: OP and OT positions of the baby at delivery (OR 0.28, CI 0.17-0.44) and inexperienced operators (OR 0.11, CI 0.02-0.58).

CONCLUSION

In this study, formal education and training of medical staff did not influence the success rate of instrumental delivery but was associated with improved safety for both mother and baby.

Obstetric vacuum extraction: state of the art in the new millennium

This article summarizes the current state of knowledge of obstetric vacuum extraction. The discussed topics include the history of vacuum extraction, indications and contraindications, technique of the procedure, currently marketed instruments, special uses of the vacuum extractor, comparison of vacuum extraction with forceps delivery, and maternal and fetal outcomes. Areas of controversy are identified and discussed. Vacuum extraction is replacing forceps as the preferred method of instrumental delivery.

Operative vaginal delivery: clinical appraisal of a new vacuum extraction device

The efficacy of a new vacuum extraction device, the Kiwi OmniCup, and its effects on mothers and infants were tested in a study of 18 non-rotational and 32 rotational vacuum assisted deliveries. Forty-nine (98%) of the extractions resulted in successful vaginal births. Autorotation of the fetal head when the occiput was transverse or posterior was achieved in 31 (97%) of the 32 vacuum procedures. The high success rates recorded for both vaginal delivery and autorotation of the fetal head were largely attributable to the fact that flexing cup applications were achieved in 90 % of the vacuum attempts. There were no cases of serious maternal trauma or clinically significant neonatal injuries. Two infants had cephalohaematomas and one infant developed a small subgaleal haemorrhage following a difficult delivery, which resolved rapidly without complications. It was concluded that the Kiwi OmniCup is an efficient and safe vacuum device for assisted vaginal delivery, provided it is used correctly and appropriately.