ICD-10-CM > O00-O9A > O20-O29 > O26 > O26.4 O26.4 Herpes gestationis Non-Billable/Non-Specific Codes O26.40Herpes gestationis, unspecified trimesterO26.41Herpes gestationis, first trimesterO26.42Herpes gestationis, second trimesterO26.43Herpes gestationis, third trimester