retrieve the ids of patients who are diagnosed with gu infection-antepartum.
select admissions.subject_id from admissions where admissions.hadm_id in ( select diagnoses_icd.hadm_id from diagnoses_icd where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'gu infection-antepartum' ) )