ICD-10-CM FY 2027 Obstetric Coding Guidelines

The FY2027 ICD-10-CM code set introduces several important additions to obstetric diagnosis coding. CMS and NCHS have declared these additions effective October 1, 2026. The FY2027 ICD-10-CM provides more specificity for several pregnancy-related conditions and provides new codes for selected obstetric and hereditary cancer-related conditions.

 

The FY2027 update changes the code set rather than the underlying Chapter 15 obstetric coding rules described below. Important additions include new codes for interstitial ectopic pregnancy (O00.12-, O00.13-), cesarean-scar ectopic pregnancy (O00.3-), cervical ectopic pregnancy (O00.4-), and cornual ectopic pregnancy (O00.5-). These code families provide greater specificity based on factors such as the presence of an intrauterine pregnancy and, where applicable, laterality.

The new O31.4- family identifies continuing pregnancy after vanishing-twin syndrome and is differentiated by trimester. Because these codes fall under category O31, the applicable 7th character is also required.

The FY2027 code set also introduces category QA1 for hereditary cancer syndromes, including Lynch syndrome (QA1.71), hereditary breast and ovarian cancer syndrome associated with BRCA1 (QA1.790) or BRCA2 (QA1.791), and Li-Fraumeni syndrome (QA1.792). These codes are found in Chapter 17 and are not obstetric codes.

General Rules for FY 2027 Obstetric Coding

Obstetric coding under Chapter 15 follows specific rules for code sequencing, trimester assignment, fetus identification, and gestational age. These rules also determine when Chapter 15 codes apply to the maternal record and how coding should be handled when an admission extends across trimesters.

Chapter 15 Codes Take Sequencing Priority

Obstetric cases are coded using Chapter 15 codes from O00-O9A, Pregnancy, Childbirth, and the Puerperium. When applicable, these codes take sequencing priority over codes from other chapters. Additional codes may be reported to provide further detail about the condition.

When the provider documents that the pregnancy is incidental to the encounter, Z33.1, Pregnant state, incidental, is used instead of a Chapter 15 code. The provider must document that the condition being treated does not affect the pregnancy.

Chapter 15 Codes Apply Only to the Maternal Record

Chapter 15 codes are assigned to the maternal record. They are not assigned to the record of the newborn.

How to Assign the Correct Trimester

Most Chapter 15 codes include a final character identifying the trimester. The appropriate trimester should be determined from the provider’s documentation of the trimester or the documented number of weeks for the current encounter.

This applies to both pre-existing conditions and conditions that develop during or result from pregnancy. If delivery occurs during the admission and an “in childbirth” option is available for the complication, that option should be assigned. If no such obstetric code is available, the code for the current trimester should be used.

Selecting the Trimester When an Admission Spans Multiple Trimesters

When a patient is admitted for a pregnancy complication in one trimester but remains hospitalized into another, the antepartum complication code should reflect the trimester in which the complication developed, rather than the trimester at discharge.

For a condition that existed before the encounter or represents a pre-existing condition, the trimester at the time of admission or encounter should be used.

When to Use an Unspecified Trimester

Codes with trimester-specific options also include an unspecified trimester option. This should be used only rarely, such as when the medical record does not provide enough information to determine the trimester and clarification cannot be obtained.

Assigning the 7th Character for Fetus Identification

Certain Chapter 15 categories require a 7th character to identify the fetus affected by the complication. These include O31, O32, O33.3-O33.6, O35, O36, O40, O41, O60.1, O60.2, O64, and O69.

The 7th character “0” is assigned when:

• The pregnancy is a single gestation.
• The documentation does not identify the affected fetus and clarification cannot be obtained.
• It is not clinically possible to determine which fetus is affected.

Coding Completed Weeks of Gestation

In ICD-10-CM, weeks of gestation are considered as completed weeks. For instance, if the provider documents a gestation of 39 weeks and 6 days, it is coded as 39 weeks because 40 weeks have not yet been completed. Z3A.39 should therefore be assigned. 

Selection of the OB Principal or First-Listed Diagnosis

Choosing the principal diagnosis for an inpatient admission or the first-listed diagnosis for an outpatient encounter depends on the nature of the obstetric encounter, whether it is a routine or high-risk pregnancy, and whether delivery takes place during the admission. Section I.C.15.b addresses five areas: routine prenatal visits, supervision of high-risk pregnancy, episodes when no delivery occurs, when a delivery occurs, and outcome of delivery. . 

Routine Outpatient Prenatal Visits

For routine outpatient prenatal visits where no complications are present, a code from Z34, Encounter for supervision of normal pregnancy, should be reported as the first-listed diagnosis.

Codes from Z34 should not be reported together with Chapter 15 codes.

Supervision of High-Risk Pregnancy

Codes from O09, Supervision of high-risk pregnancy, are intended for use only during the prenatal period. For routine outpatient prenatal visits involving a high-risk pregnancy, an O09 code should be reported as the first-listed diagnosis. Secondary Chapter 15 codes may also be assigned when appropriate.

When a high-risk pregnancy results in complications during labor or delivery, the applicable complication code from Chapter 15 should be assigned. If no complication occurs during the labor or delivery episode, O80, Encounter for full-term uncomplicated delivery, should be assigned.

When No Delivery Occurs

When an obstetric encounter does not result in delivery, the principal diagnosis should represent the main pregnancy complication responsible for the encounter.

If multiple complications are treated or monitored during the episode, any of those complication codes may be sequenced first.

When Delivery Occurs During the Admission

If the patient is admitted and delivers during the same admission, then the diagnosis for which the patient was admitted should be the principal diagnosis.

If more than one condition has led to the admission, the main condition should be the one that is best related to the delivery. A code for any complication of the delivery should be assigned as an additional diagnosis. 

For a cesarean delivery, when a condition led to the cesarean procedure, that condition should be selected as the principal diagnosis. However, if the admission was for a reason unrelated to the condition that resulted in the cesarean delivery, the condition responsible for the admission should remain the principal diagnosis.

Reporting the Outcome of Delivery

When a delivery occurs, a code from Z37, Outcome of delivery, should be included on every maternal record.

Z37 codes should not be assigned on subsequent records or on the newborn record.

Pre-Existing Conditions vs. Conditions Due to Pregnancy

Chapter 15 distinguishes certain maternal conditions based on whether they existed before pregnancy or developed during or because of the pregnancy. Determining this distinction is important when selecting the appropriate Chapter 15 code.

Identifying Pre-Existing Conditions

When a condition was present before the pregnancy, the applicable code for a pre-existing condition complicating pregnancy should be considered when available. The coding choice should be based on the provider’s documentation regarding the condition and its relationship to the pregnancy.

Identifying Pregnancy-Related Conditions

If a condition occurs during pregnancy or is directly caused by the pregnancy, the proper code for a pregnancy should be used if the classification distinguishes between the two. 

For categories that do not distinguish between pre-existing and pregnancy-related conditions, the applicable codes may be used for either situation.

Conditions Arising During the Postpartum Period

When a condition develops postpartum during the delivery encounter, codes specifically describing the puerperium may be assigned together with codes for conditions complicating pregnancy and childbirth, when appropriate.

Pre-Existing Hypertension in Pregnancy

Category O10, Pre-existing hypertension complicating pregnancy, childbirth and the puerperium, includes codes for pre-existing hypertension associated with hypertensive heart disease and hypertensive chronic kidney disease.

When an O10 code includes hypertensive heart disease or hypertensive chronic kidney disease, a secondary code from the appropriate hypertension category must also be assigned to identify the type of heart failure or chronic kidney disease that is present. 

Fetal Conditions Affecting the Management of the Mother

Categories O35, Maternal care for known or suspected fetal abnormality and damage, and O36, Maternal care for other fetal problems, are assigned when a fetal condition actually changes the management of the mother.

When O35 and O36 Codes Apply

A fetal condition supports assignment of an O35 or O36 code when it requires changes in the mother’s care, such as:

• Diagnostic studies
• Additional observation
• Special care
• Termination of pregnancy

The presence of a fetal condition alone is not sufficient to assign a code from these categories to the maternal record.

Coding In Utero Fetal Surgery

When surgery is performed on a fetus in utero, a diagnosis code from O35 should be assigned to identify the fetal condition. The appropriate procedure code should also be assigned for the surgery performed.

Perinatal codes from Chapter 16 should not be used on the maternal record to identify fetal conditions. Even when surgery is performed directly on the fetus, the encounter remains an obstetric encounter for coding purposes.

HIV and Diabetes Coding in Pregnancy

Specific sequencing and code-selection guidance are given for HIV infection, diabetes mellitus and gestational diabetes in the context of pregnancy, childbirth and the puerperium, in the FY 2027 guidelines. 

HIV Infection in Pregnancy, Childbirth, and the Puerperium

When a patient is admitted during pregnancy, childbirth, or the puerperium because of an HIV-related illness, a code from O98.7-, Human immunodeficiency [HIV] disease complicating pregnancy, childbirth and the puerperium, should be sequenced first. For symptomatic HIV disease, B20, Human immunodeficiency virus [HIV] disease, should also be assigned, followed by the code or codes identifying the HIV-related illness. 

For a patient with asymptomatic HIV infection status admitted during pregnancy, childbirth, or the puerperium, assign O98.7- together with Z21, Asymptomatic human immunodeficiency virus [HIV] infection status.

Diabetes Mellitus in Pregnancy

Diabetes mellitus is treated as a significant complicating factor during pregnancy. For a pregnant patient with diabetes, a code from O24, Diabetes mellitus in pregnancy, childbirth, and the puerperium, should be assigned first, followed by the appropriate diabetes code or codes from E08-E13.

Long-Term Use of Insulin and Oral Hypoglycemic Drugs

The guidelines also direct coders to the applicable guidance concerning the long-term use of insulin and oral hypoglycemic drugs.

Gestational Diabetes

Gestational diabetes can occur during the second and third trimesters in patients who were not diabetic before pregnancy. Codes for gestational diabetes are found in O24.4, Gestational diabetes mellitus.

No other code from category O24 should be assigned with an O24.4 code.

The O24.4 codes identify whether gestational diabetes is:

• Diet controlled
• Insulin controlled
• Controlled by oral hypoglycemic drugs

When both diet and insulin are used, only the insulin-controlled code is required. When both diet and oral hypoglycemic medication are used, only the code for control by oral hypoglycemic drugs is required.

Codes Z79.4, Z79.84, and Z79.85 should not be assigned with codes from O24.4.

For abnormal glucose tolerance in pregnancy, a code from O99.81, Abnormal glucose complicating pregnancy, childbirth, and the puerperium, should be assigned.

Sepsis and Puerperal Sepsis in Obstetric Coding

The FY 2027 guidelines provide separate instructions for sepsis complicating abortion, pregnancy, childbirth, and the puerperium and for puerperal sepsis.

Sepsis and Septic Shock Complicating Pregnancy

When a Chapter 15 code is assigned for sepsis complicating abortion, pregnancy, childbirth, or the puerperium, an additional diagnosis code should identify the specific type of infection.

When severe sepsis is present, a code from R65.2, Severe sepsis, should also be assigned along with the code or codes identifying the associated organ dysfunction.

Puerperal Sepsis

For puerperal sepsis, assign O85, Puerperal sepsis, together with a secondary code identifying the causal organism. For example, when the infection is bacterial, a code from B95-B96, Bacterial infections in conditions classified elsewhere, may be used.

Codes from A40, Streptococcal sepsis, and A41, Other sepsis, should not be assigned for puerperal sepsis.

When applicable, additional codes may be assigned for severe sepsis (R65.2-) and associated acute organ dysfunction.

O85 should not be assigned when the sepsis follows an obstetrical procedure; such cases follow the guidance for sepsis due to a postprocedural infection.

Alcohol, Tobacco, and Drug Use During Pregnancy

Specific coding guidelines are given in the FY 2027 guidelines for alcohol, tobacco, or drug use during pregnancy, childbirth, and the puerperium. There are additional codes for the related substance use that accompany the applicable Chapter 15 code. 

Alcohol Use During Pregnancy

When a patient uses alcohol during pregnancy or the postpartum period, assign a code from O99.31, Alcohol use complicating pregnancy, childbirth, and the puerperium.

A secondary code from F10, Alcohol related disorders, should also be assigned to identify manifestations of the alcohol use.

Tobacco Use During Pregnancy

When a patient uses any type of tobacco product during pregnancy or the postpartum period, assign a code from O99.33, Smoking (tobacco) complicating pregnancy, childbirth, and the puerperium.

A secondary code from F17, Nicotine dependence, should also be assigned to identify the type of nicotine dependence.

Drug Use During Pregnancy

When a patient uses drugs during pregnancy or the postpartum period, assign a code from O99.32, Drug use complicates pregnancy, childbirth, and the puerperium.

This includes illegal drugs as well as inappropriate use or abuse of prescription drugs. Secondary code(s) from F11-F16 and F18-F19 should also be assigned to identify manifestations of the drug use.

Poisoning, Toxic Effects, Adverse Effects, and Underdosing

For a pregnant patient affected by poisoning, toxic effects, adverse effects, or underdosing, a code from O9A.2, Injury, poisoning and certain other consequences of external causes complicating pregnancy, childbirth, and the puerperium, should be sequenced first.

The appropriate injury, poisoning, toxic effect, adverse effect, or underdosing code should follow, along with any additional code needed to identify the condition caused by the event.
COVID-19 in Pregnancy

When COVID-19 is the reason for the encounter during pregnancy, childbirth, or the puerperium, a code from O98.5-, Other viral diseases complicating pregnancy, childbirth and the puerperium, should be sequenced first, followed by U07.1, COVID-19.

Normal Delivery and Postpartum Coding Rules

The FY 2027 guidelines also define when O80 can be used for an uncomplicated delivery and provide specific rules for the peripartum and postpartum periods, pregnancy-related complications after six weeks, routine postpartum care, and pregnancy-associated cardiomyopathy.

When to Use Code O80 for Full-Term Uncomplicated Delivery

O80, Encounter for full-term uncomplicated delivery, should be assigned when a patient is admitted for a full-term normal delivery and delivers a single healthy infant without complications during the antepartum, delivery, or postpartum portion of the delivery episode.

O80 is always the principal diagnosis. It should not be used when another Chapter 15 code is required to describe a current complication related to the antenatal, delivery, or postnatal period.

Additional codes from other chapters may be used with O80 when they are not related to or complicating the pregnancy.

O80 When an Antepartum Complication Has Resolved

O80 may still be assigned when the patient experienced a pregnancy complication earlier in the pregnancy, provided that the complication is no longer present when the patient is admitted for delivery.

Outcome of Delivery With O80

When O80 is assigned, Z37.0, Single live birth, is the only appropriate outcome-of-delivery code.

Peripartum and Postpartum Periods

The guidelines define specific timeframes for postpartum and peripartum coding.

Defining the Postpartum Period

The postpartum period begins immediately after delivery and continues for six weeks following delivery.

The peripartum period extends from the last month of pregnancy through five months after delivery.

Postpartum Complications

A complication occurring within the six-week period following delivery is considered a postpartum complication.

Pregnancy-Related Complications After Six Weeks

Chapter 15 codes may also be used for pregnancy-related complications occurring after the peripartum or postpartum period when the provider documents that the condition is pregnancy related.

Routine Postpartum Care After Delivery Outside the Hospital

When a mother delivers outside the hospital before admission and is subsequently admitted for routine postpartum care with no complications, Z39.0, Encounter for care and examination of mother immediately after delivery, should be assigned as the principal diagnosis.

Pregnancy-Associated Cardiomyopathy

O90.3, Pregnancy associated cardiomyopathy, applies when cardiomyopathy develops as a result of pregnancy in a patient without pre-existing heart disease.

The condition may be diagnosed during the third trimester and continue to progress for months after delivery, which is why it is also referred to as peripartum cardiomyopathy.

Sequelae of Pregnancy Complications: Code O94

O94, Sequelae of complication of pregnancy, childbirth, and the puerperium, is used when an initial pregnancy complication results in a sequela that requires care or treatment at a later time.

Use of O94 After the Initial Postpartum Period

O94 may be used at any time after the initial postpartum period when the requirements for sequela coding are met.

Sequencing O94

Like other sequela codes, O94 is sequenced after the code describing the resulting sequela.

Termination of Pregnancy and Spontaneous Abortion

Termination of pregnancy and spontaneous abortion require specific sequencing based on the outcome, retained products, complications, or hemorrhage. The FY 2027 guidelines address several situations that affect how these encounters should be coded.

Abortion Resulting in a Liveborn Fetus

When an attempted termination of pregnancy results in a liveborn fetus, assign Z33.2, Encounter for elective termination of pregnancy, along with an appropriate code from category Z37 to report the outcome of delivery.

Retained Products of Conception After Abortion

If a person comes back for products of conception that were not removed after a spontaneous abortion or elective termination and there are no complications, then assign: 

• O03.4 – Incomplete spontaneous abortion without complication
• O07.4 – Failed attempted termination of pregnancy without complication

This coding applies even if the patient was previously discharged with a diagnosis of complete abortion.

If a specific complication is documented along with retained products of conception, report the applicable complication code from O03.-, O04.-, or O07.- instead of O03.4 or O07.4.

Pregnancy Complications Associated With Abortion

When a documented pregnancy complication occurs in connection with an abortion, applicable Chapter 15 codes may be reported as additional codes with codes from O04, O07, or O08.

Hemorrhage After Elective Abortion

For hemorrhage occurring after an elective abortion, assign O04.6, Delayed or excessive hemorrhage following (induced) termination of pregnancy.

Do not assign O72.1, Other immediate postpartum hemorrhage, because this code is not used for hemorrhage following an abortion.

Abuse Complicating Pregnancy

If there is suspected or confirmed abuse of a pregnant patient, then the relevant chapter 15 abuse code should be the first code in the code sequence. There are three categories identified in the guidelines: 

• O9A.3 – Physical abuse complicating pregnancy, childbirth and the puerperium 
• O9A.4 – Sexual abuse complicating pregnancy, childbirth, and the puerperium
• O9A.5 – Psychological abuse complicating pregnancy, childbirth, and the puerperium

After the applicable abuse code, assign additional codes when needed to identify an associated current injury resulting from physical or sexual abuse and the perpetrator of the abuse.

How Does BillingFreedom Manage FY2027 Obstetric Coding?

BillingFreedom's FY2027 transition begins at the diagnosis-review step, rather than following a claim denial. The OBGYN Medical Billing workflow can put the new obstetric code requirements right into claim review, where the team can validate clinical particularity prior to the diagnosis is entered into the final claim. 

Our workflow makes the FY2027 transition a claim-level coding control process rather than simply a software update. BillingFreedom’s OBGYN Medical Billing team can review the diagnosis details that actually determine code selection, helping practices move from broad or unspecified reporting toward the more specific FY2027 obstetric code structure.

To learn more about our outstanding medical billing services, you may not hesitate to get in touch with us through email at info@billingfreedom.com or by phone at +1 (855) 415-3472.