Feasibility of a RCT of techniques for managing an impacted fetal head during emergency caesarean section: the MIDAS scoping study
Authors: Walker Kate F , Mitchell Eleanor J , Ayers Susan , Jones Nia W , Ogollah Reuben , Wakefield Natalie , Dorling Jon , Pallotti Phoebe , Pillai Arani , Tempest Nicola , Plachcinski Rachel , Bradshaw Lucy , Knight Marian , Thornton Jim G 
Published: April 2023

Background
Second-stage caesarean sections, of which there are around 34,000 per year in the UK, have greater maternal and perinatal morbidity than those in the first stage. The fetal head is often deeply impacted in the maternal pelvis, and extraction can be difficult. Numerous techniques are reported, but the superiority of one over another is contentious and there is no national guidance.

Objective
To determine the feasibility of a randomised trial of different techniques for managing an impacted fetal head during emergency caesarean.

Design
A scoping study with five work packages: (1) national surveys to determine current practice and acceptability of research in this area, and a qualitative study to determine acceptability to women who have experienced a second-stage caesarean; (2) a national prospective observational study to determine incidence and rate of complications; (3) a Delphi survey and consensus meeting on choice of techniques and outcomes for a trial; (4) the design of a trial; and (5) a national survey and qualitative study to determine acceptability of the proposed trial.

Setting
Secondary care.

Participants
Health-care professionals, pregnant women, women who have had a second-stage caesarean, and parents.

Results
Most (244/279, 87%) health-care professionals believe that a trial in this area would help guide their practice, and 90% (252/279) would be willing to participate in such a trial. Thirty-eight per cent (98/259) of parents reported that they would take part. Women varied in which technique they thought was most acceptable. Our observational study found that impacted head is common (occurring in 16% of second-stage caesareans) and leads to both maternal (41%) and neonatal (3.5%) complications. It is most often treated by an assistant pushing the head up vaginally. We designed a randomised clinical trial comparing the fetal pillow with the vaginal push technique. The vast majority of health-care professionals, 83% of midwives and 88% of obstetricians, would be willing to participate in the trial proposed, and 37% of parents reported that they would take part. Our qualitative study found that most participants thought the trial would be feasible and acceptable.

Limitations
Our survey is subject to the limitation that, although responses refer to contemporaneous real cases, they are self-reported by the surgeon and collected after the event. Willingness to participate in a hypothetical trial may not translate into recruitment to a real trial.

Conclusions
We proposed a trial to compare a new device, the fetal pillow, with a long-established procedure, the vaginal push technique. Such a trial would be widely supported by health-care professionals. We recommend that it be powered to test an effect on important short term maternal and baby outcomes which would require 754 participants per group. Despite the well-known difference between intent and action, this would be feasible within the UK.

Future work
We recommend a randomised controlled trial of two techniques for managing an impacted fetal head with an in-built internal pilot phase and alongside economic and qualitative substudies.

Study registration
This study is registered as Research Registry 4942.

Funding
This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 27, No. 6. See the NIHR Journals Library website for further project information.