O99.351
Diseases of the nervous system complicating pregnancy, first trimester
This code does not map to a risk-adjusting HCC in the loaded models.
Coding notes
Excludes 1 never coded together · Excludes 2 may co-exist
conditions which complicate the pregnant state, are aggravated by the pregnancy or are a main reason for obstetric care
when the reason for maternal care is that the condition is known or suspected to have affected the fetus (O35-O36)
code to identify specific condition
supervision of normal pregnancy (Z34.-)
mental and behavioral disorders associated with the puerperium (F53.-) obstetrical tetanus (A34) postpartum necrosis of pituitary gland (E23.0) puerperal osteomalacia (M83.0)
code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known.
CODES FROM THIS CHAPTER ARE FOR USE ONLY ON MATERNAL RECORDS, NEVER ON NEWBORN RECORDS Codes from this chapter are for use for conditions related to or aggravated by the pregnancy, childbirth, or by the puerperium (maternal causes or obstetric causes) Trimesters are counted from the first day of the last menstrual period. They are defined as follows: 1st trimester- less than 14 weeks 0 days 2nd trimester- 14 weeks 0 days to less than 28 weeks 0 days 3rd trimester- 28 weeks 0 days until delivery
Official Guidelines for O99.351
FY 2026 ›Subsections
- I.C.15.aGeneral Rules for Obstetric Cases
- I.C.15.bSelection of OB Principal or First-listed Diagnosis
- I.C.15.cPre-existing conditions versus conditions due to the pregnancy
- I.C.15.dPre-existing hypertension in pregnancy
- I.C.15.eFetal Conditions Affecting the Management of the Mother
- I.C.15.fHIV Infection in Pregnancy, Childbirth and the Puerperium
- I.C.15.gDiabetes mellitus in pregnancy
- I.C.15.hLong term use of insulin and oral hypoglycemics
- I.C.15.iGestational (pregnancy induced) diabetes
- I.C.15.jSepsis and septic shock complicating abortion, pregnancy, childbirth and the puerperium
- I.C.15.kPuerperal sepsis
- I.C.15.lAlcohol, tobacco and drug use during pregnancy, childbirth and the puerperium
- I.C.15.mPoisoning, toxic effects, adverse effects and underdosing in a pregnant patient
- I.C.15.nNormal Delivery, Code O80
- I.C.15.oThe Peripartum and Postpartum Periods
- I.C.15.pCode O94, Sequelae of complication of pregnancy, childbirth, and the puerperium
- I.C.15.qTermination of Pregnancy and Spontaneous abortions
- I.C.15.rAbuse in a pregnant patient
- I.C.15.sCOVID-19 infection in pregnancy, childbirth, and the puerperium
Sections that reference O99.351
- I.C.4.bObesityChapter 4
… of the classification, such as E88.82, Obesity due to disruption of MC4R pathway; and codes in fifth character subcategory O99.21, Obesity complicating pregnancy, childbirth, and the puerperium.
- I.C.15.iGestational (pregnancy induced) diabetes
… be assigned with codes from subcategory O24.4. An abnormal glucose tolerance in pregnancy is assigned a code from subcategory O99.81, Abnormal glucose complicating pregnancy, childbirth, and the puerperium.
- I.C.15.l.1)Alcohol use during pregnancy, childbirth and the puerperium
Codes under subcategory O99.31, Alcohol use complicating pregnancy, childbirth, and the puerperium, should be assigned for any pregnancy case when a patient …
- I.C.15.l.2)Tobacco use during pregnancy, childbirth and the puerperium
Codes under subcategory O99.33, Smoking (tobacco) complicating pregnancy, childbirth, and the puerperium, should be assigned for any pregnancy case when a …
- I.C.15.l.3)Drug use during pregnancy, childbirth and the puerperium
Codes under subcategory O99.32, Drug use complicating pregnancy, childbirth, and the puerperium, should be assigned for any pregnancy case when a patient …
- I.C.15.a.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. …
Sections whose FY 2026 text names O99.351, its O99 category, or a range containing it — the chapter guidance above is the authoritative source.