Oth mult gest w two or more monochorionic fetuses, third tri

This code identifies a pregnancy involving multiple fetuses where at least two share a single chorion (monochorionic) and the pregnancy has progressed into the third trimester. It is used when the specific type of multiple gestation (e.g., monoamniotic, diamniotic) is not further specified but is known to be monochorionic.

Apply this code when documentation clearly indicates a multiple gestation with two or more monochorionic fetuses in the third trimester, and the precise amnionicity is not detailed. This is typically supported by ultrasound reports and physician notes confirming chorionicity and gestational age.

• Ensure documentation explicitly states "monochorionic" for at least two fetuses and "third trimester."
• Do not use this code if the specific type of monochorionic gestation (e.g., monoamniotic, diamniotic) is known and documented; use a more specific code from the O30.0 or O30.1 subcategories.
• Always sequence this code as a secondary diagnosis following the primary code for the pregnancy (e.g., O09.xx for supervision of high-risk pregnancy).