Table 1.

PICOS criteria for inclusion and exclusion of studies

Parameter	Inclusion criteria	Exclusion criteria
Population	Milk samples from individual healthy mothers Documented duration of pregnancy Documented lactation days Individuals with defined secretor status in the case of neutral HMOS	Animal studies Pooled milk samples Milk samples at lactation periods not fitting the lactation periods defined in this review
Intervention	None	None
Comparator	None	None
Outcomes	Absolute concentrations of a single HMOS Mean values Single HMOS concentration values with n ≥ 2 at given gestational age, secretor status, and lactation period (ie, values from at least 2 mothers were required)	Relative concentrations Concentrations of mixtures of HMOS Median values Mass spectrometry data based on universal calibration
Study design	Original articles from peer-reviewed journals	Abstracts, monographs, review articles Studies with data already reported

Abbreviations: HMOS, human milk oligosaccharides.