First steps towards core outcomes in obstetrics

by Janneke van’t Hooft

There is a widespread, unwarranted variation in reporting of outcomes in evaluation research.(1) As heterogeneity in outcomes and their measurements slows down the process of evidence synthesis and uptake, there  now seems to be a mounting interest in recent years, reflected by several publications in high impact journals, emphasising the need for standardising outcome sets as a potential solution.(2-3) In this blog, I will provide a broad overview on the movement of Core Outcome sets in the obstetrical field.

A core outcome set is a set of critical and important outcomes that should be measured and reported, as a minimum, in a standardised manner in research.(4) In other words, a core outcome set captures the key outcomes out of a variety that can be used in trials in a specific topic. This will prevent systematic reviews to compare apples with oranges, and also prevent reporting bias, as every trial will be reporting (ideally) all outcomes of the core outcome set. A standardised outcomes sets will therefore allow constructive comparison and assimilation of available evidence to maximise research impact on society. However, a core outcome set does not stop researchers to continue to explore other outcomes.

The success of core outcome set was first shown by the Outcome Measures in Rheumatology (OMERACT) initiative. The OMERACT initiative has developed core outcomes for many different rheumatological conditions. Successful implementation of the rheumatoid arthritis core outcome set has resulted in a significant change in the quality and relevance of research and enriched clinical practice by identifying new outcomes which are now routinely monitored by healthcare professionals and patients around the world.(5)

In the obstetrical field, there are now to my knowledge four core outcome set projects published. (6-9) Remarkable is the wide variation in methodology of these core outcome sets and that they are not picked up by upcoming studies yet. We are however positive that this will change in the future thanks to the work of for example the  ‘Core outcome sets in effectiveness trials’ (COMET) initiative. On their website COMET provides a database in which all planed/ongoing and completed core outcome sets per health area (or methodology used, targeted population, stakeholders involved,etc) are listed ( Furthermore, they have provided a handout on how to perform a core outcome set project (4) and are now working on a guideline for core outcome set reporting. I therefore strongly advise all parties working on a core outcome set project to register their project on the website, and therefore have some notification weather this project is already planned by other researchers or have an interface with other ongoing projects.  At the moment of writing (March 2016) the COMET website reports 25 core outcome set projects on the health area ‘pregnancy and childbirth’ covering 13 themes: preterm birth, intrauterine growth restriction, hypertensive disorders, (gestational) diabetes and overweight, induction of labour, hyperemesis gravidarum, miscarriage, reproductive disorders, endometriosis, intrauterine death/stillbirth, pain management in labour and iron deficiency anaemia, maternity care. The majority of these projects have not yet started.

COMET does also organise a yearly meeting (next meeting is on November 10-11 in Amsterdam 2016) discussing the methological chalenges and providing a broad variety of examples of core outcome set projects. Examples of methological chalenges are 1) how to properly define the target population to which the core outcome set implies; 2) how to decide on the relevant stakeholders and their global representation; 3) when and how to use the (different) consensus methods; 4) which (pre-defined) consensus criteria to use; 5) how to best report on the core outcome set; and 6) how to make sure to get the core outcome set implemented in future research, systematic reviews and guidelines.

I think especially the last point is a challenging one but is mainly influenced by how the previous points are handled. One can for example imagine that internationally developed core outcome sets have more validity and are easier to implement into clinical research worldwide. The Core Outcome in women’s Health (CROWN) is a unique journal editors initiative that is created to give a response to the urgent need to standardise the methods used to develop core outcomes sets in women’s health. By making sure that core outcome sets are developed within a high quality solid infrastructure, implementation of core outcome set will follow at much more ease.


  1. Meher S, Alfirevic Z. Choice of primary outcomes in randomised trials and systematic reviews evaluating interventions for preterm birth prevention: A systematic review. BJOG An Int J Obstet Gynaecol 2014:1-9.
  2. Porter ME, Larsson MBA, Lee TH. Standardizing Patient Outcomes Measurement. N Engl J Med 2016;374;504-6.
  3. Ioannidis JP a., Horbar JD, Ovelman CM, et al. Completeness of main outcomes across randomized trials in entire discipline: survey of chronic lung disease outcomes in preterm infants. BMJ 2015;350:e72.
  4. Williamson PR, Altman DG, Blazeby JM, et al. Developing core outcome sets for clinical trials: issues to consider. Trials 2012;13:132.
  5. Boers M, Kirwan JR, Wells G, et al. Developing core outcome measurement sets for clinical trials: OMERACT filter 2.0. J Clin Epidemiol 2014;67:745-753.
  6. Bennett WL, Robinson K a., Saldanha IJ, Wilson LM, Nicholson WK. High Priority Research Needs for Gestational Diabetes Mellitus. J Women’s Heal 2012;21:925-932.
  7. Devane D, Begley CM, Clarke M, Horey D, Oboyle C. Evaluating maternity care: A core set of outcome measures. Birth 2007;34:164-172.
  8. Fong F, Rogozinska E, Allotey J, Kempley S, Shah DK, Thangaratinam S. Development of maternal and neonatal composite outcomes for trials evaluating management of late-onset pre-eclampsia. Hypertens Pregnancy 2014;33:115-131.
  9. van ‘t Hooft J, Duffy JM, Daly M, Williamson PR, Meher S, Thom E, et al. A Core Outcome Set for Evaluation of Interventions to Prevent Preterm Birth. Obstet Gynecol. 2016;127(1):49-58.
  10. Chen YL, Yang KH. Avoidable waste in the production and reporting of evidence. Lancet. 2009;374:786
  11. Khan K. The CROWN Initiative: Journal editors invite researchers to develop core outcomes in women’s health. BJOG 2014; 126:201-2.
  12. De Wit M, Abma T, Koelewijn-van Loon M, Collins S, Kirwan J. Involving patient research partners has a significant impact on outcomes research: a responsive evaluation of the international OMERACT conferences. BMJ Open 2013;3:1-12
Posted in Core Outcome Set, preterm birth