general guidelines
a. General Rules for Obstetric Cases
1) Codes from chapter 15 and sequencing priority
Obstetric cases require codes from chapter 15, codes in the range O00-O9A, Pregnancy, Childbirth, and the Puerperium. Chapter 15 codes have sequencing priority over codes from other chapters. Additional codes from other chapters may be used in conjunction with chapter 15 codes to further specify conditions. Should the provider document that the pregnancy is incidental to the encounter, then code Z33.1, Pregnant state, incidental, should be used in place of any chapter 15 codes. It is the provider's responsibility to state that the condition being treated is not affecting the pregnancy.
"All of the O codes should be the principal diagnosis as per coding guidelines except Z33.1 if applicable"
Z3A will always be just an additional code and can't be coded alone.