The Peri/Post-natal Epigenetic Twins Study (PETS)

PETS is a study of twins, from when they were in the womb through to childhood and beyond. The study aims to identify what makes us all who we are; our health, development and well being. Where better to start than with twins, who share the same mother, but are usually in their own ‘sac’ during pregnancy, then share the same home environment as children. Despite this, even ‘identical’ twins can have different personalities, physical characteristics and illnesses. Why is this?

Study Summary
Study name The Peri/Post-natal Epigenetic Twins Study
Study abbreviation PETS
Current principal investigator/s Prof Jeffrey Craig
Richard Saffery
Current project manager

Jane Loke

Primary Institution/s Murdoch Children’s Research Institute - MCRI
Collaborating Institution/s The University of Melbourne - UoM
Deakin University
Australian Institute of Family Studies
La Trobe University
Royal Women’s Hospital
Mercy Hospital for Women
Monash Medical Centre
Major funding source/s National Health and Medical Research Council - NHMRC
Bonnie Babes Foundation
Sigrid Juselius Foundation
Academy of Finland
Finnish Cultural Foundation
Financial Markets Foundation for Children
Victorian Government’s Operational Infrastructure Support Program
Study website
Key reference for study
Study focus

Investigating whether epigenetic marks measured at birth and early life can provide clues to the causal links between intrauterine exposures influencing perinatal phenotype and the risk of chronic diseases later in life.

Sampling frame

Women attending multiple pregnancy clinics at 3 Melbourne (Australia) hospitals (Royal Women’s Hospital, Monash Medical Centre, Mercy Hospital for Women) who were 18-22 weeks gestation.

Primary study type Longitudinal cohort
Primary participant (at recruitment) Index child
Year commenced


Is this study ongoing? Yes - the study is ongoing
Ongoing recruitment? Yes
Sample size (N)

250 twin pairs and mothers

Survey data available? Yes
Imaging data available? Yes
Linkage to administrative dataset/s? No, consent to link to administrative dataset(s) obtained, but linkage not yet started
Biosamples available? Yes
Are data available to others outside study team, with appropriate safeguards and structures in line with the cohort’s ethics and governance processes? Yes
Are there any costs associated with data/sample access for approved requests? There are usually no costs associated with access
Broadest type of participant consent available Extended consent (can be used for future ethically approved research related to this project)
Wave Year Age Sample size (N)
1 2007-2009 12 weeks gestation 250 pairs
2 2007-2009 13-24 weeks gestation 250 pairs
3 2007-2009 25 weeks to Birth 250 pairs
4 2007-2009 Birth 250 pairs
5 2008-2011 18 months 250 pairs
6 2014-2016 6 years 224 pairs
7 2018-Ongoing 11 years IN PROGRESS
Study Contacts
Principal investigator/s Prof Jeffrey Craig
Richard Saffery
Project manager

Jane Loke

Study Contact

Address: PETS Study
Murdoch Children's Research Institute,
Royal Children’s Hospital
Flemington Road, Parkville
Victoria 3052 Australia