The Odon Device for assisted vaginal birth: a feasibility study to investigate safety and efficacy - the ASSIST II Study

The ASSIST Study Group

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)
103 Downloads (Pure)


The Odon Device™ is a new device for assisted vaginal birth that employs an air cuff around the fetal head for traction. Assisted vaginal birth (AVB) is a vital health intervention that can result in better outcomes for mothers and their babies when complications arise in the second stage of labour. Unfortunately, instruments for AVB (forceps and ventouse) are often not used in settings where there is most clinical need often due to lack of training and resources, resulting in maternal and neonatal morbidity and mortality which could have been prevented.

This is often due to a lack of trained operators as well as difficulties in the sterilisation and maintenance of AVB devices. This novel, single use device has the potential to mitigate these difficulties as it is single use and is potentially simpler to use than forceps and ventouse.

All the studies of the Odon Device to date (pre-clinical, preliminary developmental and clinical) suggest that the Odon Device does not present a higher risk to mothers or babies compared to current standard care, and recruitment to intrapartum research exploring the device is feasible and acceptable to women. The first study in which the Odon Device was used in clinically indicated conditions (the ASSIST Study) reported a lower efficacy than those reported with established devices. The reasons need to be explored, specifically focussing on learning curve, the technique of the doctors using this new device and potential modifications to device design. A follow-on clinical study to further investigate the efficacy and safety of the Odon Device in its indicated use, the ASSIST II Study, is therefore being undertaken.

The primary feasibility outcome is study feasibility (recruitment and retention rates) whilst the primary clinical outcome successful vaginal birth completed with the Odon Device. Key secondary feasibility outcomes include participant withdrawal, compliance in data collection and acceptability of the device to women and operators. Secondary clinical outcomes include maternal, neonatal and device outcomes. Safety data will be reviewed following every birth exploring maternal, neonatal and device risks. Using A’Hern approach for sample size calculation, we aim to recruit 104 women requiring an assisted vaginal birth for a recognised clinical indication. Assuming an AVB success rate of 65% or more, a one-sided alpha risk of 5% and power of 90%.

The data from the ASSIST II Study will provide the information required regarding acceptability, recruitment, outcome data collection, device design, technique of device use and operator learning curve in order to design a future randomised controlled trial of the Odon Device versus current modes of assisted vaginal birth.

Trial registration
ISRCTN registration: 38829082 (prospectively registered July 26, 2019)
Original languageEnglish
Article number72 (2021)
Number of pages10
JournalPilot and Feasibility Studies
Issue number1
Publication statusPublished - 19 Mar 2021


  • assisted vaginal birth
  • obstetrical vacuum extraction
  • obstetrical extraction
  • Odon Device
  • obstetrical forceps
  • feasibility studies
  • device safety
  • medical devices


Dive into the research topics of 'The Odon Device for assisted vaginal birth: a feasibility study to investigate safety and efficacy - the ASSIST II Study'. Together they form a unique fingerprint.

Cite this