Diseases of the nervous sys comp pregnancy, first trimester

This code signifies the presence of a pre-existing or new neurological disorder that is adversely affecting a patient during the first trimester of her pregnancy. This includes conditions such as epilepsy, multiple sclerosis, migraines, or Bell's palsy, where the pregnancy itself may exacerbate the condition or require special management.

Apply this code when a pregnant patient in her first trimester is diagnosed with a neurological condition that complicates the pregnancy. Documentation should clearly state the specific neurological disease and its impact or management considerations related to the pregnancy, explicitly mentioning the first trimester.

• Always sequence this code as a secondary diagnosis, following the code for the specific neurological condition.
• Ensure the medical record explicitly states "first trimester" or provides gestational age that falls within the first trimester (weeks 0-13).
• Distinguish from O99.352 (second trimester) and O99.353 (third trimester) based on documented gestational age.