Chorioamnionitis, unspecified trimester, fetus 1

This code signifies an infection of the fetal membranes (amnion and chorion) and amniotic fluid, occurring at an unspecified point during the pregnancy. It indicates that the infection affects the first fetus in a multiple gestation or is the only fetus in a singleton pregnancy.

Use this code when documentation confirms chorioamnionitis but the specific trimester of onset is not recorded. It is appropriate for cases where the infection is clearly identified as impacting the primary fetus. Documentation should explicitly state "chorioamnionitis" and indicate the affected fetus.

• Ensure documentation specifies "unspecified trimester" if the trimester is unknown; otherwise, a more specific O41.11- or O41.13- code should be used.
• Verify that the chorioamnionitis is attributed to "fetus 1" in multiple gestations.
• Do not confuse with other maternal infections during pregnancy unless chorioamnionitis is explicitly diagnosed.