title: The difficulties in establishing a birth order or maternal age effect in ankylosing spondylitis: comment on the article by Baudoin et al.
authors.affiliation: University College London, London, UK.
authors.forename: William H
authors.initials: WH
authors.lastname: James
mesh_terms: D001722:Birth Order; D005192:Family Health; D006801:Humans; D008423:Maternal Age; D009679:Nuclear Family; D013167:Spondylitis, Ankylosing / Q000503:physiopathology*