Neonatal Health and Long-Term Outcomes: Twin-Based Evidence From Linked Scandinavian Registers

Evelina Björkegren, Aline Bütikofer, Gabriella Conti, Marten Palme, Kjell G Salvanes, Palme Mårten and Daniel Björkegren

No 12958, CESifo Working Paper Series from CESifo

Abstract: This study examines the long-term consequences of neonatal health using three birth anthropometric measures — weight, length, and head circumference — and analyzes their differential associations with outcomes across the life course. Using linked Swedish and Norwegian population registers with follow-up into adulthood, we compare birth measures of singletons and twins and further estimate within-twin-pair fixed-effects models that control for shared genetic and family environmental factors. Our samples comprise up to approximately 679,000 singletons and 10,400 twins in Sweden, and 347,841 singletons and 6,762 twins in Norway, followed into adulthood. We find that different birth measures capture distinct aspects of fetal development with varying predictive validity across outcome domains. Birth length emerges as the strongest predictor of health outcomes (infant mortality, adult height), consistent with its role as a cumulative indicator of skeletal growth throughout gestation. Birth weight retains stronger associations with cognitive and educational outcomes (grade point average [GPA], years of schooling) in conditional models. Head circumference shows weak and inconsistent associations across specifications. Using within-pair head circumference differences to classify twins as symmetrically versus asymmetrically growth restricted, we find that symmetric intrauterine growth restriction is associated with substantially worse long-term outcomes than asymmetric restriction. In Norwegian twin pairs, growth restriction is associated with lower general cognitive ability (measured at military enlistment) relative to the unaffected co-twin; this within-pair deficit is more than twice as large for symmetric as for asymmetric restriction. We also document significant intergenerational transmission of birth anthropometrics, suggesting both environmental and genetic contributions. Finally, our register-based design with near-complete population coverage minimizes selection bias and attrition while providing statistical power for within-pair analyses across multiple outcomes. Exclusive reliance on birth weight may obscure important information about early-gestation developmental insults.

Keywords: birth weight; birth length; head circumference; twin studies; fetal origins; intrauterine growth restriction; linkage to administrative data (search for similar items in EconPapers)
JEL-codes: I12 I14 J13 J24 (search for similar items in EconPapers)
Date: 2026
References: Add references at CitEc
Citations:

Downloads: (external link)
https://www.ifo.de/DocDL/cesifo1_wp12958.pdf (application/pdf)

Related works:
Working Paper: Neonatal Health and Long-Term Outcomes: Twin-Based Evidence From Linked Scandinavian Registers (2026)
Working Paper: Neonatal Health and Long-Term Outcomes: Twin-Based Evidence From Linked Scandinavian Registers (2026)
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:ces:ceswps:_12958

Access Statistics for this paper

More papers in CESifo Working Paper Series from CESifo Contact information at EDIRC.
Bibliographic data for series maintained by Klaus Wohlrabe ().