Variability in reporting outcomes of clinical trials is a significant issue in obstetrics and gynaecology. In a systematic review of published randomised controlled trials (RCTs) addressing therapeutic interventions for pre-eclampsia, 79 RCTs reported 119 different maternal and infant outcomes, with significant variability with regards to what was reported.1 Most importantly, fewer than half of the studies reported any information regarding harms of the therapeutic interventions.2 Similar results have been found when reviewing clinical trials in other areas of obstetric and gynaecological research, including preterm birth,3 management of women with epilepsy in pregnancy4 and heavy menstrual bleeding trials,5 among others. This variability limits the ability to perform meaningful systematic reviews and meta-analyses and impacts on the conclusions that may be made.

What are the core outcome sets?

Core outcome sets are an agreed standardised minimum set of outcomes for clinical trials, in an attempt to reduce this variability in clinical trial reporting. They are created by consensus of multiple stakeholders, including clinicians, researchers and affected women. The development and dissemination of core outcome sets aims to standardise outcome collection and reporting in clinical trials, and allow for meaningful systematic review and meta-analysis.

‘The core outcome sets represent a minimum reporting standard for clinical trials.’

The CROWN Initiative ( represents a collective of obstetrics and gynaecology journals and journal editors who are committed to the robust development and promotion of core outcome sets. Over 80 journals are involved, including ANZJOG.6 Researchers planning trials and submitting papers to these journals are encouraged to find out if there are published core outcome sets in their areas of research and to incorporate them into trial design and reporting.

What are the core outcome sets for endometriosis?

Similar variability in reporting of outcomes in endometriosis trials is present, with a systematic review of outcome reporting revealing 164 outcomes and 113 outcome measures.7 This significantly limits the ability to draw meaningful conclusions and provide clinicians and women with evidence-based recommendations for care. The development of a core outcome set for endometriosis trials involved input from healthcare professionals, researchers and women with endometriosis. A Delphi survey was used to assess the relative importance of potential core outcomes in endometriosis research. The Delphi survey method uses multiple rounds of surveys to determine a consensus.

The final core outcome set included five core outcomes under the heading of pain, and eight core outcomes under the heading of infertility (detailed in the table below; from presentation and personal communication). While the goal is that these outcomes are addressed by all future clinical trials in endometriosis, the intention is not to limit outcome reporting, and investigation and reporting of additional outcomes of interest is encouraged.

Pain Infertility
Overall pain
Improvement in most troublesome symptom
Quality of life
Adverse events
Patient satisfaction with treatment
Viable pregnancy confirmed by ultrasound
Pregnancy loss (ectopic, miscarriage, stillbirth)
Gestational age at delivery
Time to pregnancy leading to livebirth
Neonatal mortality
Congenital abnormality


These core outcomes were presented at the FIGO World Congress 2018, in Rio de Janeiro, Brazil, by Dr James MN Duffy (@JamesMNDuffy), and are in the process of being submitted for publication.