Table 5.

Summary of potential variables included in the univariate and multivariate models.

	Explanatory variables	Design variables	Confounders
Fixed effects	Analytea IA statusb (factor) Timec Children’s analysis (continuous) Mother’s analysis (factor) IA status and time interactionc Sample IDd (factor)	Risk-sete (factor) Matching variablese Age (continuous) Sex (factor)	Confounder variables or propensity scoreeh
Random effects		Laboratory design (factors)e Motheref (factor)
Log offset		Weightseg

^aPrimary analysis only, may be either continuous or a factor (e.g. presence/absence).

^bSecondary analyses only.

^cLongitudinal analyses only.

^dMultivariate approach only, where adjusted sample analyte values are to be used which are determined based on a model with an explanatory variable relating to sample ID, discussed in Supplementary Material O.

^eDiscussed in Supplementary Material K.

^fInduces a correlation between NCC siblings who have the same mother.

^gCalculation of weights is shown in Supplementary Material J.

^hDiscussed in Supplementary Material L.