Code Obstetrical Care with Confidence

Learn ICD-10 obstetrics coding to help achieve a seamless transition from ICD-9.


ICD-10 implementation will bring lots of changes to obstetrical coding. Coders and clinicians will need to work collaboratively to achieve a seamless transition from ICD-9. Detailed clinical documentation will allow coders to assign codes to the greatest specificity. Now is a good time to review the most significant changes to obstetric coding in ICD-10.

Certified Obstetrics Gynecology Coder COBGC

ICD-10 Coding Will Be in Line with Clinical Documentation

Clinicians calculate pregnancy length based on a women’s menstrual cycle. The average menstrual cycle is 28 days. Clinicians base the length of a pregnancy on 10 cycles, or roughly 40 weeks. If a woman has a shorter cycle length, her due date would be less than 40 weeks; if a woman has a longer cycle length, her due date might be more than 40 weeks (normal pregnancy length is between 37-42 weeks). For this reason, clinicians do not talk in months of pregnancy, but rather in exact weeks and days. This is one area in ICD-10 where coding language will match medical language.

ICD-9-CM categories 640-648 and 651-676 require a fifth digit to indicate whether the encounter is antepartum or postpartum, and whether a delivery has also occurred. In ICD-10-CM, episodes of obstetric care are eliminated and replaced by trimesters. This change is a great benefit because it is much more specific to document that a women is 25 weeks gestation than to document that she is five months pregnant.

Count Weeks and Days to Find the Trimester

Trimesters are counted from the first day of the last menstrual period and, according to ICD-10-CM, are defined as:

First trimester – less than 14 weeks, 0 days

Second trimester – 14 weeks, 0 days to 28 weeks, 0 days

Third trimester – 28 weeks, 0 days until delivery

The majority of ICD-10-CM codes in chapter 15: Pregnancy, Childbirth, and the Puerperium have a final character indicating the trimester of pregnancy. The provider’s documentation of the number of weeks may be used to assign the appropriate code identifying the trimester. Assignment of the final character for trimester should be based on the provider’s documentation of the trimester (or number of weeks) for the current admission or encounter. Each category that includes trimester codes has a code for “unspecified trimester;” however, you should avoid the temptation to assign an unspecified code instead of querying the provider or reviewing the documentation. It may be easier, but it may not always be reimbursed.

Code from When Complication Care Begins

It is common for women experiencing preterm labor to be hospitalized for days, weeks, or even months. When a woman is admitted to the hospital for complications of pregnancy during one trimester, and remains in the hospital into a subsequent trimester, the trimester character for the antepartum complication code should be assigned based on when the complication developed, not the trimester at the time discharge.

Trimester Isn’t Always Coded Specifically

The trimester of pregnancy may not be indicated if a condition always occurs in a specific trimester, or the concept is not applicable. As well, certain codes have characters for only certain trimesters because the condition does not occur in all trimesters. For example, pre-eclampsia cannot occur before the 20th week of pregnancy (as such, there is no code to report first trimester):

O14.0- Mild to moderate pre-eclampsia

O14.00 unspecified trimester

O14.02 second trimester

O14.03 third trimester

O14.1- Severe pre-eclampsia

O14.10 unspecified trimester

O14.12 second trimester

O14.13 third trimester

Physician documentation must indicate the severity of the pre-eclampsia (e.g., mild to moderate or severe).

Encounters for Routine Pregnancy

ICD-9-CM offers two codes to report routine, outpatient visits for uncomplicated prenatal care. As shown in the following code comparison, ICD-10-CM includes 12 codes, four of which are unspecified.

ICD-9: V22.0 Supervision of normal first pregnancy

ICD-10: Encounter for supervision of normal first pregnancy

Z34.00 unspecified trimester

Z34.01 first trimester

Z34.02 second trimester

Z34.03 third trimester

ICD-9: V22.1 Supervision of other normal pregnancy

ICD-10: Encounter for supervision of other normal pregnancy

Z34.80 unspecified trimester

Z34.81 first trimester

Z34.82 second trimester

Z34.83 third trimester

ICD-9: No code available

ICD-10: Encounter for supervision of normal pregnancy,

Z34.90 unspecified trimester

Z34.91 first trimester

Z34.92 second trimester

Z34.93 third trimester

A code from category Z34 should be assigned as the first-listed diagnosis for routine obstetric care. Code Z34.00 should not be used after a due date has been determined, but can be used when there are unknown dates. These women are usually scheduled for an ultrasound to determine gestational age.

Coding High-risk Pregnancy

ICD-9-CM codes from category V23 describe supervision of high-risk pregnancies, and should be used as the first-listed diagnosis. There are a total of 18 codes available for reporting high-risk prenatal care in ICD-9-CM.

In ICD-10-CM, the sequencing for the first-listed diagnosis is slightly different. Prenatal outpatient visits for high-risk patients should be reported with a code from category O09 Supervision of high-risk pregnancy and should be the first-listed diagnosis. Of the 60 codes available for reporting high-risk prenatal care in ICD-10, here are a few examples:

ICD-9: V23.0 Pregnancy with history of infertility

ICD-10: Supervision of pregnancy with history of infertility

O09.00 unspecified trimester

O09.01 first trimester

O09.02 second trimester

O09.03 third trimester

ICD-9: V23.89 Other high-risk pregnancy

ICD-10: Supervision of high-risk pregnancy due to social problems

O09.70 unspecified trimester

O09.71 first trimester

O09.72 second trimester

O09.73 third trimester

Account for Multiple Gestations

Another change for ICD-10 will be code extensions to denote the specific fetus in multiple gestation pregnancies.

Most clinicians refer to multiple gestations as fetus A and fetus B. Similarly, in the nursery, clinicians refer to the babies as twin A and twin B. ICD-10 uses numbers instead of letters as the seventh character fetal extension. Where applicable, a seventh character should be assigned for certain categories to identify the fetus for which the complication code applies.

The seventh character “0” should be assigned for a single gestation when the documentation in the record is insufficient to determine the fetus affected and it is not possible to obtain clarification.

0 = not applicable or unspecified

1 = fetus 1

2 = fetus 2

3 = fetus 3

4 = fetus 4

5 = fetus 5

9 = other fetus

Timing Matters

Lastly, ICD-10 changes the timeframes for abortion vs. fetal death and early vs. late pregnancy. ICD-9-CM code 632 Missed abortion defines early death before completion of 22 weeks gestation with retention of dead fetus. ICD-10-CM code O02.1 Missed abortion defines fetal death before completion of 20 weeks gestation with retention of dead fetus. Similarly, ICD-9-CM code 640 Hemorrhage in early pregnancy is defined as hemorrhage before completion of 22 weeks; ICD-10-CM category O20 defines hemorrhage before completion of 20 weeks gestation.

Parting tip: You might have noticed throughout this article that all the ICD-10-CM codes in chapter 15 start with the letter ‘O.’ Probably one the biggest challenges we face will be keeping the ‘O’ delineated from a ‘0.’

Kerin Draak, MS, RN, WHNP-BC, CPC, CEMC, COBGC, has been in the health care field for nearly 19 years. She has more than 11 years of clinical experience in women’s health, and has been the coding educator for a 220+ multispecialty clinic since 2004. She is active in her local chapter, and a member of AAPC’s National Advisory Board (NAB).


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