Table 1.

PICOS criteria employed to the define research question

Criteria	Description
Participants	Pregnant women and their children up to 18 y of age
Intervention/exposure	In utero vitamin D status in either maternal blood or cord blood
Comparisons	Sufficient vs insufficient vitamin D status or analysis of vitamin D status by quartile
Outcomes	Primary: atopic dermatitis; allergic rhinitis; asthma; wheezing; respiratory infection; gastrointestinal tract infection Secondary: all other infections aside from maternal–fetal HIV transmission; other allergic disease; markers of allergy (e.g., total and specific IgE levels); autoimmune diseases; lung function; and other immunological outcomes related to atopy (e.g., TH1:TH2 ratio, cytokine production)
Study design	Randomized controlled trials, nonrandomized controlled trials, cohort, and case–control studies

Abbreviations: HIV, human immunodeficiency virus; IgE, immunoglobulin E.