Twin pregnancy, monochorionic/monoamniotic, unsp trimester

This code signifies a twin gestation where both fetuses share a single chorion and a single amniotic sac, indicating a high-risk pregnancy. This rare type of twin pregnancy carries increased risks of complications such as cord entanglement and twin-to-twin transfusion syndrome due to the shared environment.

Apply this code when documentation confirms a monochorionic and monoamniotic twin pregnancy, and the specific trimester is not recorded or is unknown. This diagnosis is typically established via ultrasound imaging that clearly identifies a single placenta and a single amniotic sac containing both fetuses.

• Ensure documentation explicitly states "monochorionic" and "monoamniotic" for accurate coding.
• If the trimester is known, use the more specific O30.011, O30.012, or O30.013 codes.
• Always sequence this code as a primary diagnosis when it is the main reason for the encounter, or as a secondary diagnosis when managing complications related to the twin pregnancy.