title: [Clarifications on observational studies and on the prevalence].
authors.affiliation: Hospital Materno Perinatal Mónica Pretelini, Instituto de Salud del Estado de México, Toluca, Estado de México, México, iliana.espinoza@espm.insp.mx.
authors.forename: Iliana
authors.initials: I
authors.lastname: Espinoza-Rivera
mesh_terms: D006801:Humans; D015995:Prevalence