Table 1.

PICO-Scheme

	Inclusion criteria	Exclusion criteria
POPULATION	all births, term/ normal birth weight birth or low risk birth in a nationwide setting with < 5/1000 neonatal deaths	Preterm birth, low birth weight birth, other risk-selections (e.g. gestational diabetes, multiple births)
EXPOSITION	comparison of different hospital birth volumes or -sizes	No comparison of different hospital birth volumes or -sizes
COMPARISON	other birth volumes	No comparator provided
OUTCOME	Primary Outcome: Maternal or infant mortality Secondary Outcomes: Caesarean sections, readmissions, birth complications, developmental delays	No measurement of maternal or infant mortality
STUDY TYPE	Observational and interventional studies	Descriptive studies, systematic reviews