Chapter 15 — Pregnancy, Childbirth and the Puerperium
Chapter 15 codes outrank every other chapter. Trimester characters, the O80 normal-delivery rule, Z37 on every delivery record, and the conditions that complicate pregnancy.
One rule governs the whole chapter: Chapter 15 codes have sequencing priority over codes from every other chapter. Codes from other chapters may be added to further specify conditions, but the obstetric code leads. The only way out is Z33.1 — and only the provider can put you there, by stating that the pregnancy is incidental to the encounter.
General rules for obstetric cases#
| # | Rule | Detail |
|---|---|---|
| 1 | Sequencing priority | Obstetric cases require codes from O00–O9A. Chapter 15 codes have sequencing priority over codes from other chapters. Additional codes from other chapters may be used with them to further specify conditions. Where the provider documents that the pregnancy is incidental to the encounter, Z33.1 is 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 |
| 2 | Maternal record only | NEVER Chapter 15 codes are used only on the maternal record, never on the record of the newborn |
| 3 | Final character for trimester | Most Chapter 15 codes have a final character for the trimester. Assignment is based on the provider's documentation of the trimester, or the number of weeks, for the current admission or encounter — and this applies to pre-existing conditions as well as to those that develop during pregnancy. Where delivery occurs during the current admission and an “in childbirth” option exists for the complication, assign the “in childbirth” code; where the classification has no such option, assign a code describing the current trimester |
| 4 | Admissions spanning more than one trimester | The trimester character for an antepartum complication code is assigned on the basis of the trimester when the complication developed, not the trimester of discharge. If the condition developed prior to the current admission or is pre-existing, assign the trimester at the time of the admission or encounter |
| 5 | Unspecified trimester | Each category with trimester codes has an unspecified-trimester code, which should rarely be used — only where the documentation is insufficient and clarification cannot be obtained |
| 6 | 7th character for fetus identification | Applies to categories O31, O32, O33.3–O33.6, O35, O36, O40, O41, O60.1, O60.2, O64 and O69. Assign 7th character 0 for single gestations, where the documentation is insufficient to determine the affected fetus and clarification cannot be obtained, and where it is not possible to clinically determine which fetus is affected |
| 7 | Completed weeks of gestation | “Completed” weeks means full weeks. Gestation documented at 39 weeks and 6 days is coded as 39 weeks, because 40 completed weeks has not been reached |
Selecting the obstetric principal or first-listed diagnosis#
| Episode | First-listed / principal | Notes |
|---|---|---|
| Routine outpatient prenatal visit, no complications | A code from category Z34 | NEVER Not used in conjunction with chapter 15 codes |
| Routine prenatal outpatient visit, high-risk pregnancy | A code from category O09 | O09 is for use only during the prenatal period. Secondary chapter 15 codes may be used with it if appropriate |
| Complications during the labour or delivery episode as a result of a high-risk pregnancy | The applicable complication codes from Chapter 15 | If there are no complications during labour or delivery, assign O80 |
| Episodes when no delivery occurs | The principal complication of the pregnancy which necessitated the encounter | Where more than one complication exists and all are treated or monitored, any of them may be sequenced first |
| When a delivery occurs | The condition that prompted the admission | If multiple conditions prompted the admission, sequence the one most related to the delivery. A code for any complication of the delivery is an additional diagnosis |
| Cesarean delivery | The condition the patient was admitted with that resulted in the cesarean | If the reason for admission was unrelated to the condition resulting in the cesarean, the condition related to the reason for admission is the principal diagnosis |
| Every maternal record where a delivery has occurred | A code from category Z37 Outcome of delivery must be included | NEVER Not used on subsequent records and never on the newborn record |
Normal delivery — code O80#
| Point | Rule |
|---|---|
When O80 applies | A patient admitted for a full-term normal delivery who delivers a single, healthy infant without any complications antepartum, during the delivery, or postpartum during the delivery episode |
| Sequencing | ALWAYS O80 is always a principal diagnosis |
| When it cannot be used | NEVER Not used if any other chapter 15 code is needed to describe a current complication of the antenatal, delivery or postnatal period |
| Other chapters | Additional codes from other chapters may be used with O80 if they are not related to or in any way complicating the pregnancy |
| Resolved antepartum complication | O80 may be used where the patient had a complication at some point during the pregnancy but it is not present at the time of the admission for delivery |
| Outcome of delivery | Z37.0 single live birth is the only outcome of delivery code appropriate for use with O80 |
Conditions complicating pregnancy#
| Condition | Codes and sequence |
|---|---|
| Pre-existing versus pregnancy-related | Certain categories distinguish conditions that existed prior to pregnancy from those that are a direct result of pregnancy. Categories that do not distinguish may be used for either. Codes specifically for the puerperium may be used with codes complicating pregnancy and childbirth if a condition arises postpartum during the delivery encounter |
Pre-existing hypertension — category O10 | Includes codes for hypertensive heart and hypertensive chronic kidney disease. When assigning an O10 code that includes those, add a secondary code from the appropriate hypertension category to specify the type of heart failure or chronic kidney disease |
| HIV — symptomatic disease or HIV-related illness | 1O98.7-2B203code(s) for the HIV-related illness(es) |
| HIV — asymptomatic infection status | 1O98.7-2Z21 |
| Pre-existing diabetes mellitus | 1O24.-2the appropriate E08–E13 code(s) |
Gestational (pregnancy induced) diabetes — subcategory O24.4 | NEVER No other code from category O24 is used with a code from O24.4. The O24.4 codes include diet controlled, insulin controlled and controlled by oral hypoglycemic drugs. Diet and insulin → only the insulin-controlled code. Diet and oral drugs → only the oral-controlled code. NEVER Z79.4, Z79.84 and Z79.85 are not assigned with O24.4 |
| Abnormal glucose tolerance in pregnancy | O99.81- |
| Sepsis complicating abortion, pregnancy, childbirth and the puerperium | 1the chapter 15 sepsis code2a code for the specific type of infection3R65.2- and organ dysfunction codes if severe sepsis is present |
Puerperal sepsis — O85 | 1O852a secondary code identifying the causal organism, for example from B95–B963R65.2- and acute organ dysfunction codes if applicable |
What O85 is not for | NEVER Codes from A40 or A41 are not used for puerperal sepsis. NEVER O85 is not assigned for sepsis following an obstetrical procedure — see Section I.C.1.d.5.b |
| Alcohol use during pregnancy or postpartum | 1O99.31-2a secondary code from category F10 to identify manifestations |
| Tobacco use during pregnancy or postpartum — any type of tobacco product | 1O99.33-2a secondary code from category F17 to identify the type of nicotine dependence |
| Drug use during pregnancy or postpartum — illegal drugs, or inappropriate use or abuse of prescription drugs | 1O99.32-2secondary code(s) from F11–F16 and F18–F19 |
| Poisoning, toxic effects, adverse effects and underdosing in a pregnant patient | 1O9A.2-2the injury, poisoning, toxic effect, adverse effect or underdosing code3additional code(s) specifying the condition caused |
| Abuse of a pregnant patient | 1O9A.3- physical, O9A.4- sexual or O9A.5- psychological abuse2codes for any associated current injury3the perpetrator code, if applicable |
| Malignant neoplasm in a pregnant patient | 1O9A.1-2the appropriate Chapter 2 code for the type of neoplasm |
| COVID-19 as the reason for admission or encounter | 1O98.5-2U07.13codes for associated manifestations |
| COVID-19 diagnosed during an admission for an unrelated reason | 1the reason for the admission or encounter2O98.5-3U07.14codes for associated COVID-19 manifestations |
Fetal conditions, the puerperium and abortion#
| Topic | Rule |
|---|---|
Categories O35 and O36 | Assigned only when the fetal condition is actually responsible for modifying the management of the mother — by requiring diagnostic studies, additional observation, special care, or termination of pregnancy. NEVER The mere existence of the fetal condition does not justify a code from this series |
| In utero surgery | Assign a code from O35 identifying the fetal condition, plus the appropriate procedure code. NEVER No code from Chapter 16 is used on the mother's record to identify fetal conditions. Surgery performed in utero on a fetus is still coded as an obstetric encounter |
| Postpartum period | Begins immediately after delivery and continues for six weeks following delivery. A postpartum complication is any complication occurring within that six-week period |
| Peripartum period | The last month of pregnancy to five months postpartum |
| Pregnancy-related complications after the peripartum or postpartum period | Chapter 15 codes may still be used if the provider documents that the condition is pregnancy related |
| Routine postpartum care after delivery outside the hospital | Where the mother delivers outside the hospital prior to admission and is admitted for routine postpartum care with no complications, Z39.0 is the principal diagnosis |
Pregnancy associated cardiomyopathy — O90.3 | May be diagnosed in the third trimester but may continue to progress months after delivery, hence “peripartum cardiomyopathy”. Used only where the cardiomyopathy develops as a result of pregnancy in a patient who did not have pre-existing heart disease |
O94 Sequelae of complication of pregnancy, childbirth and the puerperium | For cases where an initial complication develops a sequela requiring care at a future date. May be used at any time after the initial postpartum period, and like all sequela codes is sequenced following the code describing the sequela |
| Attempted termination resulting in a liveborn fetus | 1Z33.2 Encounter for elective termination of pregnancy2a code from category Z37 |
| Retained products of conception following spontaneous abortion or elective termination, without complications | O03.4 or O07.4 — appropriate even where the patient was previously discharged with a diagnosis of complete abortion. Where there is a specific complication in addition to retained products, assign the complication code (O03.-, O04.-, O07.-) instead |
| Complications leading to abortion | Chapter 15 codes may be used as additional codes to identify documented complications, with codes in O04, O07 and O08 |
| Haemorrhage following elective abortion | O04.6. NEVER Do not assign O72.1, which is not for post-abortion conditions |
Practice questions#
Q1A patient at 30 weeks is admitted with acute appendicitis and undergoes appendectomy. The pregnancy continues normally and the provider does not document the pregnancy as incidental. What is the principal diagnosis?
- AThe acute appendicitis
- BA code from Chapter 15 for the condition complicating pregnancy, followed by the appendicitis code
- C
Z33.1followed by the appendicitis - D
Z34.-
Show answer & rationale
Correct answer: B. A code from Chapter 15 for the condition complicating pregnancy, followed by the appendicitis code
Rationale. Guideline I.C.15.a.1 states that obstetric cases require codes from chapter 15, that chapter 15 codes have sequencing priority over codes from other chapters, and that additional codes from other chapters may be used in conjunction with chapter 15 codes to further specify conditions. Z33.1 is used in place of chapter 15 codes only where the provider documents that the pregnancy is incidental to the encounter — and the guideline places that responsibility on the provider.
Q2A patient with gestational diabetes is managed with both diet and insulin. What is assigned?
- AThe
O24.4diet-controlled code andZ79.4 - BOnly the
O24.4insulin-controlled code - CThe
O24.4insulin-controlled code andZ79.4 - DA code from
O24.0-O24.3plusZ79.4
Show answer & rationale
Correct answer: B. Only the O24.4 insulin-controlled code
Rationale. Guideline I.C.15.i states that if a patient with gestational diabetes is treated with both diet and insulin, only the code for insulin-controlled is required, and that codes Z79.4, Z79.84 and Z79.85 should not be assigned with codes from subcategory O24.4. It also states that no other code from category O24 should be used with a code from O24.4.
Q3A patient is admitted at 39 weeks and 6 days for a full-term normal delivery. She delivers a single healthy infant with no complications at any point. What is assigned?
- A
O80andZ37.0, with the gestation coded as 40 weeks - B
O80andZ37.0, with the gestation coded as 39 weeks - C
O80andZ37.9 - D
Z34.9andZ37.0
Show answer & rationale
Correct answer: B. O80 and Z37.0, with the gestation coded as 39 weeks
Rationale. Guideline I.C.15.n.1 makes O80 always the principal diagnosis for a full-term normal delivery of a single healthy infant with no complications, and I.C.15.n.3 states that Z37.0 is the only outcome of delivery code appropriate for use with O80. Guideline I.C.15.a.7 defines completed weeks of gestation as full weeks and uses this precise example: 39 weeks and 6 days is coded as 39 weeks, because 40 completed weeks has not been reached.
Q4An ultrasound identifies a fetal anomaly. The provider documents it but the anomaly does not require any diagnostic studies, additional observation, special care or termination, and does not change the management of the mother. What is assigned?
- AA code from category
O35 - BA code from Chapter 17 on the mother's record
- CNo code from
O35orO36 - DA code from category
O36with 7th character 0
Show answer & rationale
Correct answer: C. No code from O35 or O36
Rationale. Guideline I.C.15.e.1 states that codes from categories O35 and O36 are assigned only when the fetal condition is actually responsible for modifying the management of the mother — by requiring diagnostic studies, additional observation, special care or termination of pregnancy — and that the fact that the fetal condition exists does not justify assigning a code from this series to the mother's record.
Q5A patient delivers at home and is admitted for routine postpartum care. No complications are documented. What is the principal diagnosis?
- A
O80 - B
Z39.0 - C
Z37.0 - DA code from
Z34
Show answer & rationale
Correct answer: B. Z39.0
Rationale. Guideline I.C.15.o.4 states that when the mother delivers outside the hospital prior to admission and is admitted for routine postpartum care with no complications noted, code Z39.0, encounter for care and examination of mother immediately after delivery, should be assigned as the principal diagnosis. Z37 outcome codes are for the delivery record and are always secondary.
Scenarios#
A patient is admitted at 26 weeks with pre-eclampsia that developed in the second trimester. She remains hospitalised and is discharged at 29 weeks, in the third trimester, without delivering.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | O14.02 / O14.12 | Pre-eclampsia, the applicable severity, with the trimester character for the second trimester — verify in the Tabular List |
| 2 | Z3A.26 | 26 weeks gestation of pregnancy |
Rationale. Guideline I.C.15.a.4 states that where a patient is admitted for complications of pregnancy during one trimester and remains in the hospital into a subsequent trimester, the trimester character for the antepartum complication code is assigned on the basis of the trimester when the complication developed, not the trimester of discharge. Guideline I.C.15.b.3 makes the principal complication the principal diagnosis in episodes where no delivery occurs. Section I.C.21.c.11 directs that for inpatient admissions spanning more than one gestational week, the date of admission determines the Z3A code.
Guideline: Section I.C.15.a.4, I.C.15.b.3, I.C.21.c.11
A patient is admitted at 38 weeks with severe pre-eclampsia. Labour is induced; during labour, fetal distress develops and an emergency cesarean is performed. A single live infant is delivered.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | O14.13 | Severe pre-eclampsia, third trimester — principal diagnosis, the condition that prompted the admission and is most related to the delivery |
| 2 | O36.83X0 | Maternal care for other specified fetal problems — or the applicable fetal distress code with the 7th character for the fetus; verify in the Tabular List |
| 3 | Z3A.38 | 38 weeks gestation of pregnancy |
| 4 | Z37.0 | Single live birth |
Rationale. Guideline I.C.15.b.4 states that when an obstetric patient is admitted and delivers during that admission, the condition that prompted the admission is sequenced as the principal diagnosis, and that where multiple conditions prompted the admission the one most related to the delivery is sequenced first. For cesarean delivery it adds that if the patient was admitted with a condition that resulted in the cesarean, that condition is the principal diagnosis. Guideline I.C.15.b.5 requires a Z37 code on every maternal record where a delivery has occurred, and I.C.15.a.6 governs the 7th character for fetus identification.
Guideline: Section I.C.15.a.6, I.C.15.b.4, I.C.15.b.5
A patient develops sepsis following an infected cesarean section wound. Severe sepsis with acute kidney injury is documented.
Show coded answer & rationale
| Seq | Code | Description |
|---|---|---|
| 1 | O86.0- | Infection of obstetric surgical wound, the applicable site code — sequenced first |
| 2 | O86.04 | Sepsis following an obstetrical procedure |
| 3 | B95 / B96 | An additional code to identify the infectious agent |
| 4 | R65.20 | Severe sepsis without septic shock |
| 5 | N17.9 | Acute kidney failure, unspecified |
Rationale. Guideline I.C.1.d.5.b governs sepsis due to a postprocedural infection and names the obstetric codes directly: for sepsis following a postprocedural wound infection, a code from O86.00 to O86.03 or O86.09 identifying the site is sequenced first if known, followed by O86.04 sepsis following an obstetrical procedure, with an additional code for the infectious agent and, where severe sepsis is present, R65.2- plus organ dysfunction codes. Guideline I.C.15.k is explicit that O85 puerperal sepsis is not assigned for sepsis following an obstetrical procedure.
Guideline: Section I.C.1.d.5.b, I.C.15.k
Primary sources#
- ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027CMS — the source document for every page on this site (effective 1 Oct 2026)
- NCHS ICD-10-CM files — Tabular List, Index, POA exempt listOfficial code files, addenda and the list of codes exempt from POA reporting
- ICD-10 Coordination and Maintenance CommitteeWhere code proposals are debated; agendas, summaries and meeting materials
- CMS ICD-10 homeCode sets, transition guidance and Medicare coding policy
- AHA Coding ClinicOfficial coding advice from the AHA Central Office — subscription required
- HHS OIG Work PlanActive audit topics — useful for prioritising internal coding audits
- MEDESUN Medical Coding AcademyTraining, credential preparation and audit services by the author