Twin pregnancy, monochorionic/diamniotic, third trimester

This code signifies a twin gestation where both fetuses share a single chorion but have separate amniotic sacs, and the pregnancy is currently in the third trimester. This specific chorionicity and amnionicity combination carries distinct risks and management considerations compared to other twin types.

Apply this code when documentation clearly indicates a monochorionic/diamniotic twin pregnancy that has progressed into the third trimester (typically beginning at 28 weeks gestation). This diagnosis is typically established via ultrasound and confirmed by the physician.

• Ensure documentation explicitly states "monochorionic/diamniotic" and "third trimester."
• Do not confuse with monochorionic/monoamniotic or dichorionic/diamniotic twin pregnancies, which have different codes.
• Sequence this code as the primary diagnosis when it is the main reason for the encounter, or as a secondary diagnosis when monitoring is for other conditions during this type of twin pregnancy.