O26.42 Herpes gestationis, second trimester

Billable ICD-10-CM code, FY2026.

MS-DRG index

Defines the logic of DRG(s) 817-819 in MDC 14.

Approximate ICD-9-CM (GEMs)

• 646.81 Other specified complications of pregnancy, delivered, with or without mention of antepartum condition (approximate)
• 646.83 Other specified complications of pregnancy, antepartum condition or complication (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Maternity diagnoses (age 9 through 64): Age conflict edit. These diagnoses are clinically expected only in patients age 9 through 64.

Code annotations containing back-references to O26.42

Back-references to O26.4

• Type 1 Excludes: L12 Pemphigoid ("herpes gestationis (O26.4-)")
• Type 2 Excludes: O98 Maternal infectious and parasitic diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium ("herpes gestationis (O26.4-)")
• Type 2 Excludes: O99.7 Diseases of the skin and subcutaneous tissue complicating pregnancy, childbirth and the puerperium ("herpes gestationis (O26.4)")

Back-references to O26

• Type 1 Excludes: Z03.7 Encounter for suspected maternal and fetal conditions ruled out ("known or suspected fetal anomalies affecting management of mother, not ruled out (O26.-, O35.-, O36.-, O40.-, O41.-)")

Nearby codes

• O26.32 Retained intrauterine contraceptive device in pregnancy, second trimester
• O26.33 Retained intrauterine contraceptive device in pregnancy, third trimester
• O26.4 Herpes gestationis
• O26.40 Herpes gestationis, unspecified trimester
• O26.41 Herpes gestationis, first trimester
• O26.42 Herpes gestationis, second trimester (this code)
• O26.43 Herpes gestationis, third trimester
• O26.5 Maternal hypotension syndrome
• O26.50 Maternal hypotension syndrome, unspecified trimester
• O26.51 Maternal hypotension syndrome, first trimester
• O26.52 Maternal hypotension syndrome, second trimester