Pregnancy Nutrition Core Outcome Set (PRENCOS)



At PRENCOS, we are trying to create a Core Outcome Set for Pregnancy Nutrition Research (PRENCOS). This will be a list of outcomes that healthcare professionals, researchers and women with experience of pregnancy all agree are most important for studies looking at diet during pregnancy. When PRENCOS is used in future studies, it will help standardise which outcomes are studied. This will help us create strong evidence that can will inform the dietary advice given to pregnant women.

We are looking for people to take part in our online survey

We will ask you to complete a short online survey called a Delphi survey, which will have two rounds. In the survey, you will be asked to vote on how important you think each outcome is to include in the core outcome set. Lot's of outcomes are important for health during pregnancy but PRENCOS will be a list of outcomes that are essential for all studies to measure going forward. 
Register here to have your say:

If you are interested in learning more, please see our infographic 

Background to PRENCOS

What is an outcome?

In research when something is measured e.g. a change after a treatment, we call it an outcome. When planning a study, researchers pick the outcomes they will measure. The change in the outcomes will show if the study treatment had any effect.  

Choosing an outcome to measure

If different types of outcomes are measured in studies for the same health problem or treatments, it means researchers cannot compare or combine the results from different studies. This makes it hard to know which treatment is the best one.

For example, two different studies in pregnant women are happening at the same time. Both studies are testing the same treatment - giving women a leaflet on how to eat more fruit and vegetables. Study One will measure the effect of the leaflet on the number of apples eaten in a week. Study Two will measure the effect of the leaflet on the total number of any type of fruit eaten in a week. 

In this example, even though the studies are very similar, the results cannot be compared or combined because the outcomes they chose to measure were different. 

What is a Core Outcome Set?

A Core Outcome Set (COS) is a list of the most important outcomes to measure for a specific condition or treatment. They are created to encourage researchers to measure these outcomes as a minimum. If more studies, follow the COS then more research can be used to find out what treatments work for certain populations. The COS is only the minimum number of outcomes that should be measured, and it will not stop studies from measuring other outcomes that are important for their new research question.


There are lots of studies looking at different diets in pregnancy, but they do not agree on what are the most important outcomes to measure. In fact, about half of all outcomes measured in diet studies during pregnancy were only measured in one study!

How will we create PRENCOS?

A COS needs involvement from the right people. For our study, we need women who are mothers or who are currently pregnant to participate. We also need healthcare professionals who care for pregnant women and researchers who study the effects of diet during pregnancy to be involved. Together, everyone will vote and agree on what outcomes are the most important to measure for all studies on diet in pregnancy.


For more information, please see our infographic and study protocol.


There are four main steps:

  1. Systematic Review: This is a summary of all the research studies looking at what a woman eats during pregnancy. The systematic review will tell us the outcomes measured and reported in these studies. We will create a long list of every outcome reported in these studies.
  2. Interviews with women: The long list of outcomes from the systematic review shows what healthcare professionals and researchers choose to measure in studies. It is important to ask women with personal experience of pregnancy what they think should be measured. We will do this by interviewing women.
  3. Online Delphi Survey: Delphi surveys are a type of survey that is sent out more than once to groups of people who agree to take part. The PRENCOS survey will ask women, healthcare professionals and researchers to look at our long list of outcomes created from the interviews and systematic review steps. We will do two rounds of this Delphi survey. The survey will ask everyone to rate how important they think each outcome is to be included in the PRENCOS.

Round1: The full list of outcomes is sent out to all the women, healthcare professionals and researchers taking part. They will score the importance of each outcome.

Round 2: All the women, healthcare professionals and researchers taking part. are shown the results from round 1 for each group. They will also be reminded what they scored each outcome in round 1. Based on this feedback, each person will have the chance to change their score or keep their round 1 scores for each outcome.

4. Consensus Meeting: Holding a consensus or agreement meeting is the last step in making a COS. a small group of those who took part in the Delphi Survey will be invited to the meeting. In this meeting, the outcomes that groups did not agree on in the Delphi Survey will be discussed. The meeting will end with a final vote on which outcomes are included in the PRENCOS.