Herpes gestationis, first trimester

This code describes pemphigoid gestationis (also known as herpes gestationis), an autoimmune blistering skin condition that occurs during pregnancy. It is characterized by intensely pruritic, erythematous plaques and bullae, typically appearing in the second or third trimester but can manifest earlier. The condition is not related to the herpes simplex virus.

Use this code when documentation confirms a diagnosis of pemphigoid gestationis occurring specifically during the first trimester of pregnancy. This diagnosis should be supported by clinical findings and, often, immunofluorescence studies. Ensure the trimester is clearly documented to justify the specific trimester-based code.

• Confirm the trimester of pregnancy is explicitly documented as "first trimester" to support this specific code.
• Do not confuse this autoimmune condition with actual herpes simplex virus infections; they are distinct.
• Always sequence this code as a secondary diagnosis following the appropriate code for the pregnancy itself (e.g., from category Z3A).