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 name The Peri/Post-natal Epigenetic Twins Study
Study abbreviation PETS
Current principal investigator/s A/Professor Jeff Craig
Dr Richard Saffery
Current project manager Jane Loke
Phone + 61 3 9936 6549
Primary Institution Murdoch Children’s Research Institute
Collaborating Institution/s University of Melbourne
Deakin University
Australian Institute of Family Studies
LaTrobe University
Royal Women’s Hospital
Mercy Hospital for Women
Monash Medical Centre
Major funding sources National Health and Medical Research Council
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/s
  • Saffery, R., Morley, R., Carlin, J.B., Joo, J.H.E., Novakovic, B., Andronikos, R., Ollikainen, M., Li, X., Loke, Y.J., Carson, N., Wallace, E.M., Umstad, M.P., Permezel, M., Galati, J. and Craig, J.M. (2012). Cohort Profile: Peri/postnatal Epigenetics Twins Study. International Journal of Epidemiology, 41, 55-61. doi: 10.1093/ije/dyr140
  • Loke Y.J., Novakovic B., Ollikainen M., Wallace E.M., Umstad, M.P., Permezel M., Morley R., Ponsonby A.L., Gordon L., Galati J.C., Saffery R. and Craig J.M. (2013) The Peri/Postnatal Epigenetic Twins Study (PETS). Twin research and human genetics: the official journal of the International Society for Twin Studies, 16, 13-20. doi: 10.1017/thg.2012.114 
  • Leong P, Loke YJ, Saffery R, Silk T, Burnett A, Josev E, Scurrah K, Theda C, Czajko A, Pua EP, Seal ML, Craig JM. Epigenetic influences on neurodevelopmental at 11 years of age: Protocol for the longitudinal peri/postnatal epigenetic twins study at 11 years of age (PETS@11). Twins Res. Hum. Genet. 2020 Feb. doi: 10.1017/thg.2019.120
Are data available to others outside study team? Yes, with custodian approval
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
Year commenced 2007
Commencement sample 250 twin pairs and mothers
Imaging Ultrasound data including Doppler
Linkage No 
Biosamples? Blood
Cord blood
Newborn screening (Guthrie) card
Placenta (sample)
Umbilical cord (sample)
Ethics approvals or requirements? This project only (Specific consent)
Future research related to this project (Extended consent)


Wave Year Age (mean, range) Eligible sample
1  2007 – 2009 < 12 weeks gest 250
2  2007 – 2009 13-24 weeks gest 250
3  2007 – 2009 25 weeks to birth 250
4  2007 – 2009 Birth 250
5  2008 – 2011 18 months 250
6  2014 – 2016 6 years 224
7  2018 – 2020 11 years 111