Development of a core outcome set for effectiveness studies of breech birth at term (Breech-COS): A systematic review on variations in outcome reporting

Women pregnant with a breech-presenting fetus at term are at an increased risk of adverse outcomes. Although the most common intervention is planned delivery by caesarean section, this is not always possible or desirable. Comparing alternative interventions is difficult due to heterogeneity in reported outcomes and their measurements. Additionally, the evidence, particularly for women in labour with a breech-presenting fetus, is very low quality, with several outcomes viewed as critical and important to decision-making not reported at all. There is a need to develop a core outcome set of minimum outcomes in all studies evaluating the effectiveness of interventions to improve outcomes associated with term breech birth (Breech-COS). Our objectives were to (1) identify outcomes currently reported in effectiveness studies of breech birth at term using a systematic review of the literature; (2) assess the methodological quality of outcome reporting in the included studies; and (3) engage with members of an established Patient and Public Involvement (PPI) group about the results, to help frame our understanding from the perspective of service users. We searched three databases (MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials) for all effectiveness studies associated with vaginal breech birth published in English between 2000 and 2020. Two reviewers independently screened and extracted the data. Outcomes were categorised into neonatal, maternal, features of labour, and long-term maternal and hierarchy of outcome classification (primary, secondary, part of composite, or undesignated). Frequency of reporting was calculated for each. An adapted methodological assessment was done for each study investigating whether primary and secondary objectives were clearly stated and defined. The results of the systematic review were then discussed with a PPI group to consider importance and relevance to service users. A total of 211 outcomes were extracted from 108 included studies, comprising of short (43) and long-term (39) neonatal, short (54) and long-term (39) maternal and features of labour (36) outcomes. The most frequently reported outcome in each category was: APGAR score at 5 min, developmental vulnerability/neurological morbidity, maternal mortality, urinary incontinence, and actual mode of birth respectively. Long-term outcomes were infrequently reported in the included studies, with outcomes for future pregnancies not reported at all, although these were each deemed important by service users. There was a lack of consensus in definition and measurement of outcomes, with only 36% of the included studies having clearly stated primary and secondary objectives. The observed heterogeneity in reported outcomes, lack of consensus in definition and measurement, as well as desire expressed by service users to have robust risk statistics for outcomes important to them highlights the need to develop a core outcome set for evaluating effectiveness studies of breech birth at term. A Breech-COS will enable useful synthesis of evidence and contribute to supported decision-making for women pregnant with a breech-presenting fetus at term.