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

Selection of the apposite vacuum extractor during operative delivery: A biomechanical study

BACKGROUND

Operative delivery is a technique used during vaginal or cesarean birth to facilitate the patient's labor course through the assistance of a vacuum extractor. This method is increasingly used compared with forceps. This study aimed to investigate the forced effects of vacuum extractors comprising vacuum cups with different thicknesses on the fetal head and the vacuum extractor during vacuum-assisted delivery and to determine the optimal thickness for reducing the failure rate and minimizing neonatal and maternal morbidity.

METHODS

A biomechanical model was developed to examine the impact of vacuum cups with varying thicknesses. This simulation three-dimensional (3D) geometry model was used to evaluate hemispherical-shaped vacuum extractors made of silicone rubber having a similar cup diameter of 70 mm with varying thicknesses (1-5 mm), which were applied to the three models (flat surfaces, hemispherical balls, and fetal head). Under one boundary condition and two different loading conditions, finite element analysis was utilized to simulate the force of vacuum extractors on the fetal head during the process of operative delivery. The main observation indicators were the reaction forces of the constructed model, and von Mises stress on both the vacuum extractors and fetal head.

RESULTS

For the reaction forces on each axis, we found that the sum of the reaction force values on each axis was increased as the thickness of the vacuum extractor was increased, regardless of the surface type. In addition, the reaction force of the fixed-support end was increased with the increased thickness of the vacuum extractor. The von Mises stress distributions of vacuum extractors comprising vacuum cups with different thicknesses, revealed that the thinner the cup, the greater the von Mises stress exerted on the extractor itself regardless of the surface type. The distribution of von Mises stress on the skull structure of the fetal head showed that the thinner the cup, the greater the von Mises stress exerted on the skull structure regardless of the surface type.

CONCLUSION

A thinner vacuum extractor cup may result in greater injury to the fetus; hence, a thicker vacuum extractor cup is preferably utilized during vacuum-assisted operative delivery. Using a thicker vacuum extractor should yield a higher successful delivery rate and reduce fetal injury.

Investigating the Effects of Different Sizes of Silicone Rubber Vacuum Extractors during the Course of Delivery on the Fetal Head: A Finite Element Analysis Study

During certain clinical situations, some parturients require instruments for operative vaginal delivery, and various designs of vacuum extractors may affect the fetal head. To investigate the biomechanical effects of divergent sizes of silicone rubber vacuum extractors, we employed finite element analysis in this study. First, we constructed computer models for different vacuum extractor sizes (diameters: 40 mm, 50 mm, 60 mm, and 70 mm), flat surface, hemispherical ball, and fetal head shape. A hemispherical ball was the main design for the vacuum extractor model, and the material used for the vacuum extractor was silicone rubber. Next, the settings of 1 mm vacuum extractor displacement and vacuum cap pressure of 60 cmHg were applied. The main observation markers of this study were the respective von Mises stresses on the vacuum extractor and skull by the reaction force on the fixed end. The concluded results revealed that vacuum extractors with larger diameters lead to greater reaction force, stress, and strain on fetal heads. Therefore, this study's biomechanical analytic consequences suggest that clinicians avoid selecting larger vacuum extractors during operative instrumental delivery so that fetal heads will experience less external force, deformation, and resultant complications. It could also provide a practical reference for obstetricians for instrumental vaginal delivery with the vacuum extractor made of silicone rubber.

Instruments for assisted vaginal birth

BACKGROUND

Assisted vaginal births are carried out to expedite birth for the benefit of mothers and babies but are sometimes associated with significant morbidity for both. Various instruments are available, broadly divided into forceps and vacuum cups, and choice may be influenced by clinical circumstances, operator preference, experience and availability.  OBJECTIVES: To evaluate the different instruments in terms of success in achieving a vaginal birth, and the risk of morbidity for mother and baby.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (14 May 2021), and reference lists of retrieved studies.

SELECTION CRITERIA

We selected randomised controlled trials of assisted vaginal birth using different instruments. The review did not include quasi-randomised trials, cluster-randomised trials or cross-over designs. The review included trials for which abstracts alone were available as long as there was sufficient information to assess eligibility.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. We used the GRADE approach to assess the certainty of evidence.  The main outcomes assessed included failed delivery with allocated instrument, any maternal trauma, third- and fourth-degree tears, postpartum haemorrhage, any neonatal trauma, low Apgar and low umbilical artery pH.  MAIN RESULTS: We included 31 studies involving a total of 5754 women.  Risk of bias criteria were largely assessed as 'unclear', due to a lack of detail in trial reports. Blinding would have been challenging for all trials due to their inability to conceal the type of instrument used from either the woman or the operator, which is reflected in the risk of bias assessment. Any type of forceps versus any type of vacuum cup (12 studies, 3129 women) Forceps may be less likely to fail in achieving vaginal birth: risk ratio (RR) 0.58, 95% confidence interval (CI) 0.39 to 0.88; 11 studies, 3080 women; low certainty. 'Any maternal trauma' may be slightly more likely with forceps: odds ratio (OR) 1.53, 95% CI 0.98 to 2.40; 5 studies, 1356 women; low certainty; and third- or fourth-degree tears may also be more likely with forceps: RR 1.83, 95% CI 1.32 to 2.55; 9 studies, 2493 women; low certainty. There is no evidence of a difference in the incidence of postpartum haemorrhage (PPH) between the two groups: RR 1.71, 95% CI 0.59 to 4.95; 2 studies, 523 women; low certainty, because the evidence is very imprecise due to a very wide CI.  More women in the forceps group reported requiring pain relief. There is probably no evidence of difference in rates of low Apgar: RR 0.83, 95% CI 0.46 to 1.51; 7 studies, 1644 women; moderate certainty; or low umbilical artery pH in the forceps group compared to any vacuum: RR 1.33, 95% CI 0.91 to 1.93; 2 studies, 789 women; low certainty; both of these outcomes are imprecise and have wide CIs that include both benefit and harm. There were also lower rates of fetal trauma with 'any forceps' (cephalhematoma, retinal haemorrhage and jaundice). The composite outcome of 'any neonatal trauma' was not reported. Low-cavity forceps versus any vacuum cup (2 studies, 218 women) We included two small studies with 218 participants in this comparison, but we judged most of the evidence as very low certainty, hence it was not feasible to make judgements on the difference in the rates of failed delivery, any maternal trauma or third- and fourth- degree tears. PPH and low umbilical artery pH were not reported. Soft vacuum cup versus any rigid cup (9 studies, 1148 women) Failed delivery may be more likely in the soft vacuum cup group: RR 1.62, 95% CI 1.21 to 2.17; 9 studies, 1148 women; low certainty. There may be no difference in the rates of 'any maternal trauma': OR 0.63, 95% CI 0.24 to 1.67; 2 studies, 348 women; low certainty, but the confidence interval is wide, indicating possible benefit or harm. There may be no difference in the rates of third- or fourth-degree tears: RR 0.93, 95% CI 0.35 to 2.44; 4 studies, 619 women; low certainty. There is probably no difference in the rates of PPH: RR 0.89, 95% CI 0.49 to 1.61; 5 studies, 737 women; moderate certainty between the soft and rigid cup groups.   There may be little or no difference in the incidence of low Apgar scores: RR 0.82, 95% CI 0.49 to 1.37; 9 studies, 1148; low certainty; or low umbilical artery pH: RR 0.80, 95% CI 0.47 to 1.36; 1 study, 100 women; low certainty. Handheld vacuum versus any vacuum cup (4 studies, 968 women) There may be no difference in the rates of failures with allocated instrument: RR 1.35, 95% CI 0.81 to 2.25; 4 studies, 962 women; low certainty, any maternal trauma: OR 1.16, 95% CI 0.71 to 1.88; 2 studies; 394 women; low certainty, PPH: RR 0.31, 95% CI 0.03 to 2.92; 1 study, 164 women; low certainty, low umbilical artery pH: RR 1.06, 95% CI 0.71 to 1.59; 1 study, 164 women; low certainty, or low Apgar scores: RR 1.25, 95% CI 0.34 to 4.61; 3 studies, 784 women; low certainty) between the two groups. There is probably no difference in the rates of third- or fourth-degree tears between the 'handheld vacuum' and 'any vacuum cup' groups: RR 1.15, 95% CI 0.62 to 2.12; 4 studies, 962 women; moderate certainty.

AUTHORS' CONCLUSIONS

This review provides low-certainty evidence that forceps may be more likely to achieve vaginal birth and have lower rates of fetal trauma, but at a greater risk of perineal trauma and higher pain relief requirements compared with vacuum cups. There was low-certainty evidence that rigid vacuum cups may be more likely to achieve a vaginal birth than soft cups but with more fetal trauma, whilst handheld vacuum cups had similar success rates compared to other cups. There was no evidence of a difference in the rates of third- or fourth-degree tears or postpartum haemorrhages between types of cups, but wide confidence intervals around the estimates indicate further research is needed in this area.

Exploring the reporting standards of RCTs involving invasive procedures for assisted vaginal birth: A systematic review

OBJECTIVE

Assisted vaginal birth (AVB) is a complex intervention involving medical devices, comprising multiple components. This complexity creates difficulties when designing and conducting randomised controlled trials (RCTs), in terms of describing, standardising and monitoring the intervention, and accounting for differing clinician expertise. This review examines the reporting standards of complex interventions involving a medical device, in the context of AVB RCTs.

STUDY DESIGN

Searches were undertaken from the start of indexing to March 2021, and limited to RCTs, feasibility and pilot studies including at least one device for AVB. RCTs were selected if they included participants having an AVB with any device, with or without a comparator group. Reporting details were assessed according to the Consolidating Standards of Reporting Trials extension for non-pharmacological treatments (CONSORT-NPT), focusing on intervention descriptions, standardization, adherence and clinician expertise. Screening of abstracts, full-text articles and data extraction was performed by two independent reviewers.

RESULTS

Of 4098 abstracts and 83 full-text articles, 39 papers were included, investigating 80 interventions. Twenty-seven different named devices were identified. Intervention descriptions were provided in 20 (55%) papers with varying levels of detail and with only one covering the entire procedure. Standardization of interventions was mentioned in 25 papers (64%). Only eight (21%) papers reported any form of adherence to the intended procedure. Some data regarding expertise were reported in 25 (64%) papers.

CONCLUSIONS

Despite some compliance with reporting standards, there is a lack of detail regarding intervention description, standardization, adherence and expertise in RCTs of AVB. This creates difficulties in understanding how intervention delivery was intended and what actually occurred. Clearer guidelines for the reporting of invasive procedures and devices are required.

Vacuum extraction for non-rotational and rotational assisted vaginal birth

Vacuum-assisted birth is a safe mode of birth in the presence of a skilled provider. Vacuum extraction can avoid prolonged second stage of labour, birth asphyxia in the presence of foetal distress or maternal pushing where contraindicated. Vacuum-assisted births - particularly those in midpelvic rotational births - have been increasingly traded for caesarean births, although the latter are generally associated with potentially a greater risk to women and (future) children. In this article, (contra)indications and the basics of vacuum technique are elaborated. A specific section is dedicated to vacuum extraction for rotational birth. If these techniques are known, trained and practiced by obstetric care givers, then vacuum extraction has tremendous potential to make childbirth safer.

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.

Impact of increasing capacity for generating and using research on maternal and perinatal health practices in South East Asia (SEA-ORCHID Project)

BACKGROUND

Maternal and neonatal mortality and morbidity remain unacceptably high in many low and middle income countries. SEA-ORCHID was a five year international collaborative project in South East Asia which aimed to determine whether health care and health outcomes for mothers and babies could be improved by developing capacity for research generation, synthesis and use.

METHODS

Nine hospitals in Indonesia, Malaysia, the Philippines and Thailand participated in SEA-ORCHID. These hospitals were supported by researchers from three Australian centres. Health care practices and outcomes were assessed for 1000 women at each hospital both before and after the intervention. The capacity development intervention was tailored to the needs and context of each hospital and delivered over an 18 month period. Main outcomes included adherence to forms of care likely to be beneficial and avoidance of forms of care likely to be ineffective or harmful.

RESULTS

We observed substantial variation in clinical practice change between sites. The capacity development intervention had a positive impact on some care practices across all countries, including increased family support during labour and decreased perineal shaving before birth, but in some areas there was no significant change in practice and a few beneficial practices were followed less often.

CONCLUSION

The results of SEA-ORCHID demonstrate that investing in developing capacity for research use, synthesis and generation can lead to improvements in maternal and neonatal health practice and highlight the difficulty of implementing evidence-based practice change.