7Custovic A, Simpson BM, Simpson A, et al. Manchester asthma and allergy study: Low-allergen environment can be achieved and maintained during pregnancy and in early life[ J].J Allergy Clin Immunol, 2000,105:252-258.
8William CM. Asthma in pregnancy[ J]. Clln Obstet and Gynecol, 1996,39( 1 ) :56.