Twin pregnancy, monochorionic/diamniotic, first trimester

This code identifies a pregnancy involving two fetuses that share a single placenta but have separate amniotic sacs, specifically when the gestational age is within the first trimester. This type of twin pregnancy carries unique risks due to the shared placenta.

This code is used when ultrasound imaging confirms a monochorionic/diamniotic twin gestation and the patient is in the first trimester (up to the end of the 13th week of gestation). Documentation should clearly specify the chorionicity and amnionicity, as well as the gestational age.

• Ensure documentation explicitly states "monochorionic" and "diamniotic" for accurate coding.
• Verify the gestational age to confirm the first trimester; codes exist for subsequent trimesters.
• Do not confuse with dichorionic/diamniotic twin pregnancies, which have separate placentas.