Obstetric (O) codes and trimesters, delivery and outcome codes, newborn records, and behavioral health — depression, anxiety and substance use.
Pregnancy codes come first
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Chapter 15 (O00–O9A) codes have sequencing priority over other chapters when the patient is pregnant — unless the provider documents that the pregnancy is incidental to the visit (then Z33.1 pregnant state, incidental).
• Routine prenatal visit, no complications → Z34.- (first pregnancy Z34.0-, other Z34.8-) — not with O codes.
• High-risk supervision → O09.- (e.g. elderly multigravida O09.52-).
• Most O codes have a final character for trimester: 1st (less than 14 weeks 0 days), 2nd (14w0d to less than 28w0d), 3rd (28w0d until delivery).
• Z3A.- weeks of gestation codes are added when documented.