Twin pregnancy, monochorionic/monoamniotic, second trimester

This code signifies a pregnancy involving two fetuses that share a single placenta (monochorionic) and a single amniotic sac (monoamniotic), identified during the second trimester. This is a high-risk pregnancy due to potential complications such as twin-to-twin transfusion syndrome and umbilical cord entanglement.

Use this code when documentation clearly indicates a monochorionic/monoamniotic twin gestation confirmed in the second trimester. This diagnosis is typically established via ultrasound findings. The second trimester is defined as weeks 14 through 27+6 days of gestation.

• Ensure documentation explicitly states "monochorionic" and "monoamniotic" in addition to "twin pregnancy."
• Verify the gestational age falls within the second trimester (weeks 14-27+6).
• Do not confuse with dichorionic/diamniotic or monochorionic/diamniotic twin pregnancies, which have different code assignments.