Feasibility and design of a trial regarding the optimal mode of delivery for preterm birth: the CASSAVA multiple methods study

Jane E. Norman (Lead / Corresponding author), Julia Lawton, Sarah J. Stock, Dimitrios Siassakos, John Norrie, Nina Hallowell, Sushila Chowdhry, Ruth I. Hart, David Odd, Jane Brewin, Lucy Culshaw, Caroline Lee-Davey, Hannah Tebbutt, Sonia Whyte

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Background: Around 60,000 babies are born preterm (prior to 37 weeks' gestation) each year in the UK. There is little evidence on the optimal birth mode (vaginal or caesarean section).

Objective: The overall aim of the CASSAVA project was to determine if a trial to define the optimal mode of preterm birth could be carried out and, if so, determine what sort of trial could be conducted and how it could best be performed. We aimed to determine the specific groups of preterm women and babies for whom there are uncertainties about the best planned mode of birth, and if there would be willingness to recruit to, and participate in, a randomised trial to address some, but not all, of these uncertainties. This project was conducted in response to a Heath Technology Assessment programme commissioning call (17/22 'Mode of delivery for preterm infants').

Methods: We conducted clinician and patient surveys (n = 224 and n = 379, respectively) to identify current practice and opinion, and a consensus survey and Delphi workshop (n = 76 and n = 22 participants, respectively) to inform the design of a hypothetical clinical trial. The protocol for this clinical trial/vignette was used in telephone interviews with clinicians (n = 24) and in focus groups with potential participants (n = 13).

Results: Planned sample size and data saturation was achieved for all groups except for focus groups with participants, as this had to be curtailed because of the COVID-19 pandemic and data saturation was not achieved. There was broad agreement from parents and health-care professionals that a trial is needed. The clinician survey demonstrated a variety of practice and opinion. The parent survey suggested that women and their families generally preferred vaginal birth at later gestations and caesarean section for preterm infants. The interactive workshop and Delphi consensus process confirmed the need for more evidence (hence the case for a trial) and provided rich information on what a future trial should entail. It was agreed that any trial should address the areas with most uncertainty, including the management of women at 26-32 weeks' gestation, with either spontaneous preterm labour (cephalic presentation) or where preterm birth was medically indicated. Clear themes around the challenges inherent in conducting any trial emerged, including the concept of equipoise itself. Specific issues were as follows: different clinicians and participants would be in equipoise for each clinical scenario, effective conduct of the trial would require appropriate resources and expertise within the hospital conducting the trial, potential participants would welcome information on the trial well before the onset of labour and minority ethnic groups would require tailored approaches.

Conclusion: Given the lack of evidence and the variation of practice and opinion in this area, and having listened to clinicians and potential participants, we conclude that a trial should be conducted and the outlined challenges resolved.

Future work: The CASSAVA project could be used to inform the design of a randomised trial and indicates how such a trial could be carried out. Any future trial would benefit from a pilot with qualitative input and a study within a trial to inform optimal recruitment.

Limitations: Certainty that a trial could be conducted can be determined only when it is attempted.

Trial registration: Current Controlled Trials ISRCTN12295730.

Original languageEnglish
Pages (from-to)1-102
Number of pages102
JournalHealth Technology Assessment
Issue number61
Publication statusPublished - Nov 2021


  • COVID-19
  • Cesarean Section
  • Feasibility Studies
  • Humans
  • Infant
  • Infant, Newborn
  • Infant, Premature
  • Manihot
  • Pandemics
  • Pregnancy
  • Premature Birth/epidemiology
  • SARS-CoV-2


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