In simple words: This code is used when the delivery of twins is difficult because the babies are positioned in a way that they are locked together.

This code describes a situation where the delivery of twins is obstructed specifically due to the twins being interlocked, preventing natural progression of labor.

Example 1: A pregnant woman carrying twins presents in labor. Upon examination, it is determined that the twins are locked, preventing vaginal delivery.Code O66.1 is assigned., A woman is in labor with twins.During delivery, the first twin is delivered, but the second twin becomes locked with the first. Code O66.1 is applied., A woman at 37 weeks gestation is admitted for a planned cesarean section due to the anticipated difficulty of delivering interlocked twins. During the cesarean, the interlocked position is confirmed. Code O66.1 is used to document the obstruction.

Documentation should clearly indicate the diagnosis of locked twins as the cause of the obstructed labor. The type of locking (e.g., head-to-head, head-to-body) should be noted, if known. Any procedures performed to resolve the obstruction, such as cesarean delivery,should also be documented. Imaging studies that helped establish the diagnosis of interlocked twins should be referenced.

** This code describes a specific type of obstructed labor. Other codes exist for other causes of obstructed labor, such as shoulder dystocia (O66.0) or large fetal size (O66.2).