title: Letter: Oral contraception and sex ratio at birth.
mesh_terms: D001755:Blastocyst / Q000276:immunology; D003276:Contraceptives, Oral / Q000009:adverse effects; D010064:Embryo Implantation / Q000187:drug effects; D005260:Female; D006648:Histocompatibility / Q000187:drug effects; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects; D011247:Pregnancy; D012744:Sex Ratio
chemical_list: D003276:Contraceptives, Oral