Individual Study / EXPRESS

EXPRESS - Extremely Preterm Infants in Sweden Study

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The EXPRESS Study (Extremely Preterm Infants in Sweden Study) is comprised of a group of liveborn and stillborn extremely preterm (EPT) infants born at a gestational age of <27 weeks, recruited over a 3 year period between 2004 and 2007 in Sweden.
The primary aims of the EXPRESS study are to determine perinatal and infant mortality and morbidity by gestational age in weeks, to identify risk factors for adverse outcomes, and to evaluate long-term health among infants born EPT.



Investigators Contacts
  • Karel Marsal
    Lund University Hospital
  • Karin Källén
    Lund university


Start Year
Follow Up Is Ongoing
Year of Most Recent Data Collection
New Data Collection planned?


Access to external researchers or third parties neither provided nor foreseen.

Data (questionnaire-derived, measured...)
Other access

Supplementary Information

A 4th collection event is ongoing.

Study Design

Study design
Number of Data Collection Events
Number of very preterm (VPT) and/or very low birthweight (VLBW) births included in cohort (live & still births)

Marker Paper

Fellman V, Hellstrom-Westas L, Norman M, Westgren M, Kallen K, Lagercrantz H, Marsal K, Serenius F, Wennergren M. One-year survival of extremely preterm infants after active perinatal care in Sweden. JAMA. 2009;301(21):2225-33.

Collaborators: Blennow M, Ewald U, Fritz T, Holmgren PA, Jeppsson A, Lindberg E, Lundqvist A, Lindeberg SN, Olhager E, Ostlund I, Simic M, Sjörs G, Stigson L, Fellman V, Hellström-Westas L, Norman M, Westgren M, Holmström G, Laurini R, Stjernqvist K, Källén K, Lagercrantz H, Marsál K, Serenius F, Wennergren M, Nilstun T, Olausson PO, Strömberg B. JAMA 2009;301(21):2225-33.

PUBMED 19491184



Population based cohort consisting of all live born (gestational age equal to or less than 26 weeks+6 days) and stillborn infants (gestational age 22+0 weeks–26 +6 weeks) delivered extremely preterm in Sweden from April 1, 2004, to March 31, 2007.
Selection Criteria
  • Sweden
Geographical Area
All of Sweden
VPT/VLBW Group Inclusion Criteria
The study population comprised all live-born (gestational age <27+0 weeks) and stillborn infants (gestational age 22+0 weeks – 26+6 weeks) delivered extremely preterm in Sweden from April 1, 2004, to March 31, 2007.
Control Group Inclusion Criteria
Selection criteria for controls were singleton at-term birth with a 5-minute Apgar score greater than 3 with matching of control participants for place of living, sex, day of birth, and maternal country of birth.
VPT/VLBW Group Exclusion Criteria
Women delivering extremely preterm but not residing in Sweden in study period. Terminations of pregnancy and infants born outside of Sweden and transferred to Sweden for neonatal care were also excluded.
Control Group Exclusion Criteria
Data Collection Events
# Name Description Start End
0 Perinatal Assessment Data were collected prospectively by local hospital staff and cross-linked with the National Medical Birth Registry to ensure the accuracy of the information captured. Data on mothers and still ... 2004 2007
1 2.5 year Follow Up Participants were assessed at 30 months by a psychologist and pediatrician or pediatric neurologist.

The Bayley Scales of Infant and Toddler Development – Third Edition (Bayley-III) ...
2006 2010
2 6.5 year Follow Up Participants were assessed at 6.5 years of age. Cognitive function was assessed with the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV). A neuropediatric assessment was ... 2010 2014