ICD-10-CM > O00-O9A > O20-O29 > O24 > O24.8 > O24.81 O24.81 Other pre-existing diabetes mellitus in pregnancy Non-Billable/Non-Specific Codes O24.811Other pre-existing diabetes mellitus in pregnancy, first trimesterO24.812Other pre-existing diabetes mellitus in pregnancy, second trimesterO24.813Other pre-existing diabetes mellitus in pregnancy, third trimesterO24.819Other pre-existing diabetes mellitus in pregnancy, unspecified trimester