Obstetrical Inpatient Diagnosis Coding – A Refresher

Obstetrical Inpatient Diagnosis Coding


Obstetrics is to coding as cats are to animal lovers, you either love or dislike that subset of coding (or the animal kingdom) and there’s no in-between. Sometimes a refresher of the highlights related to obstetrical coding can be beneficial for ensuring accurate coding for this type of record or even re-ignite an interest and fondness for the genre.

At baseline, the coder should be thoroughly familiar with the chapter-specific coding guidelines for Chapter 15: Pregnancy, Childbirth and the Puerperium (O00-O9A) of the ICD-10-CM Official Guidelines for Coding and Reporting. Some key points of the guidelines for the more common circumstances include:

· Chapter 15 codes have sequencing priority over codes from other chapters but additional codes from other chapters may be used in conjunction with the Chapter 15 codes to provide further specificity.

· It is the provider’s responsibility to state that the condition being treated is not affecting the pregnancy.

· If the provider specifically documents that the pregnancy is incidental to the encounter, code to Z33.1. Otherwise, use the appropriate Chapter 15 code.

· Most of the codes in Chapter 15 have a final character indicating the trimester of the pregnancy; assignment is based on the provider’s documentation of the number of weeks for the current admission/encounter.

· Whenever a delivery occurs during the current admission and if there is an “in childbirth” option for the obstetric complication being coded, the “in childbirth” final character should be assigned.

· When delivery occurs during the admission, the condition that prompted the admission should be sequenced as the principal diagnosis. If multiple conditions prompted the admission, sequence the one most related to the delivery as the principal diagnosis.

· Chapter 15 distinguishes between conditions of the mother that pre-existed prior to pregnancy (e.g. O10, pre-existing hypertension complicating pregnancy, childbirth and the puerperium) and those that are a direct result of pregnancy (e.g. O24.4-, gestational diabetes mellitus).

· Code categories O35 and O36 are to be used for maternal care related to known or suspected fetal abnormality and damage as well as other fetal problems; they are only to be assigned when the fetal condition is directly responsible for modifying the management of the mother.

· Codes from subcategories O99.31-, O99.32- and O99.33- for alcohol, drug and tobacco use, respectively, should be assigned for any pregnancy when a mother uses these substances during the pregnancy or postpartum period.

· When COVID-19 is the reason for admission, code O98.5-. Other viral diseases complicating pregnancy, childbirth and the puerperium, should be sequenced as the principal diagnosis, and code U07.1, COVID-19 and the appropriate codes for any associated manifestation(s) should be assigned as additional diagnoses.

· If the reason for admission is unrelated to COVID-19 but the patient tests positive for COVID-19 during the hospital stay, the appropriate reason for the admission should be sequenced as the principal followed by the O98.5- and U07.1 and any associated manifestation codes.

· A code from category Z37, outcome of delivery, should be assigned on every maternal record when a delivery occurs.


The antepartum period is from conception to childbirth

The peripartum period is the last month of pregnancy to five months postpartum

The postpartum period (or puerperium) begins immediately after delivery and continues for six weeks following delivery.

The provider’s documentation of the number of weeks may be used to assign the appropriate code identifying the trimester:

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

Code any current maternal conditions that impact the care of the pregnant patient, meeting additional diagnosis criteria that requires:

o Clinical evaluation

o Therapeutic treatment

o Diagnostic procedures

o Extended length of hospital stay

o Increased nursing care and/or monitoring

Categories O20-O29 address maternal disorders that are predominantly related to pregnancy.

23-week maternity patient admitted for IV fluids due to vomiting related to the pregnancy – Code to O21.2, Late vomiting of pregnancy.

Categories O98- and O99- describe infectious and parasitic diseases and other diseases respectively that are classified elsewhere but are complicating the pregnant state. The ICD-10-CM manual provides additional direction under the code subcategories indicating the code range of conditions included.

A patient with a history of hypothyroidism who is maintained on Synthroid delivers a healthy full-term baby – Add codes O99.284 (Endocrine, nutritional and metabolic diseases complicating childbirth) + E03.9 (hypothyroidism)

Code any complications related to labor & delivery.

Mother presents at 27 weeks with premature rupture of membranes 30 hours prior and onset of labor 2 hours ago – code to O42.112, Preterm premature rupture of membranes, onset of labor more than 24 hours following rupture, second trimester.

Code any postpartum complications.

Following c-section delivery three days prior, patient developed severe pain in the right leg. Ultrasound was performed which was negative; pain attributed to varicose vein – code to O87.4, Varicose veins of lower extremity in the puerperium + I83.811, Varicose veins of right lower extremity with pain.

Do not assign BMI code (Z68.-) for obese or overweight patients who are pregnant.

Refer to Coding Clinic for further advice on specific obstetrical coding scenarios.

AHA’s ICD-10-CM and ICD-10-PCS Coding Handbook is a good resource for providing supplemental guidance in pregnancy coding. You can purchase your own copy here.

To read more MRA coding blog, check out our blog page here.

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