Clinical impact of the disposable ventouse iCup® versus a metallic vacuum cup: a multicenter randomized controlled trial

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.

The role of mediolateral episiotomy during vacuum-assisted vaginal delivery with soft cup devices

PURPOSE

This study evaluated whether episiotomy during vacuum-assisted delivery leads to fewer third- and fourth-degree tears.

METHODS

This was a retrospective cohort study of all nulliparas who underwent a singleton, soft cup, vacuum-assisted vaginal delivery in one institution, from January 2014 to August 2019. Failed vacuum deliveries were excluded. Based on power analysis calculation, a sample size of 500 women in each group was sufficient to detect an advantage of episiotomy, if present. Primary outcome was third- or fourth-degree perineal tear. Secondary outcomes were other maternal complications, and low neonatal cord pH and Apgar scores. Outcomes were compared between women with and without episiotomy.

RESULTS

During the study period, 2370 nulliparas had a vacuum-assisted vaginal delivery using soft vacuum cup and met the study inclusion criteria. Episiotomy was performed in 1868 (79%) women, and 502 (21%) delivered without episiotomy. Background characteristics were similar in both groups. There were no significant differences in the rates of third and fourth grade perineal lacerations between the two groups. Episiotomy was associated with higher rate of postpartum hemorrhage (p < 0.01) CONCLUSIONS: Using selective episiotomy for patients delivering vaginally with the assistance of soft cap vacuum does not increase third- or fourth-degree perineal tears.

Which technique is better to place a manoeuvrable vacuum extractor cup on the flexion point? Vacca vs. Bird technique

Objectives The purpose of this study is to compare the vacuum extractor cup application technique described by Bird vs. the technique described by Vacca on a simulation model. Methods Six obstetricians participated in the study. Each obstetrician performed eight vacuum assisted deliveries using the Bird technique and eight vacuum assisted deliveries using the Vacca 5-Steps technique. Results A total of 96 vacuum assisted deliveries were performed. The mean distance from the centre of the cup to the flexion point was 1.78±0.96 cm for the Bird technique and 1.05±0.60 cm for the Vacca technique (p<0.001). The lateral distance (over the parietal bone) was 1.16±0.69 cm for the Bird technique and 0.66±0.52 cm for the Vacca technique (p<0.001). The vertical distance (towards the frontal or occipital bone) was 1.12±1.02 cm for the Bird technique and 0.67±0.55 cm for the Vacca technique (p=0.009). In occipito anterior positions, there were no significant differences between both techniques. Conclusions The Vacca technique was better in transverse and posterior positions.

Kiwi omnicup handheld versus Mityvac M-style conventional vacuum system: a retrospective observational study

INTRODUCTION

To improve the choice of vacuum-assisted delivery (VAD) system, we compared the outcomes of Kiwi handheld system and Mityvac M-style conventional system (both use disposable plastic cups).

MATERIALS AND METHODS

Retrospective observational study with data collection from electronic medical records. The study was conducted at a tertiary medical center, with approximately 7000 deliveries annually. Categorical and continuous variables were analyzed using chi-square test and t-test, respectively. p value < .05 was considered significant. The main outcomes assessed were the overall failure rate of each system, failure rates for occipito-anterior (OA) versus occipito-transverse/occipito-anterior (OT/OP) positions, +1 versus +2 fetal stations, and early maternal/neonatal outcomes.

RESULTS

During a 10-month period, there were 507 (8.4%) attempted VADs, 36 failed (7.1%), and eight (1.5%) converted to cesarean section. Of these, 364 were Kiwi-assisted and 143 Mityvac-assisted. Background characteristics were similar. The handheld system had more failures overall (9.6 versus 0.7%), at OA (7.6 versus 0.9%), and non-OA positions (17.3% versus none), at +1 (13.25 versus 0.96%) and at +2/3 stations (6.1% versus none), than the conventional system did, respectively. There was a higher rate of early post-partum hemorrhage (15.3 versus 7.4%) in the conventional group. Both systems had similar rates of third/fourth degree perineal tears, shoulder dystocia and adverse neonatal outcomes.

CONCLUSIONS

Our results suggest more failures with Kiwi compared to Mityvac, overall and at any fetal position/station, without a significant difference in adverse outcome profile.