By Eman Zahra
Sixteen New Ectopic Pregnancy Codes, and One Trap
Before October 1, 2026, ICD-10-CM named three ectopic sites: abdominal, tubal and ovarian. Everything else went to O00.80 or O00.81, other ectopic pregnancy without or with an intrauterine pregnancy.
The FY 2027 update adds sixteen codes covering four sites that were previously invisible: interstitial, cesarean scar, cervical and cornual. For obstetrics and emergency medicine this is the most clinically significant part of the release.
It also contains the single most likely coding error in the FY 2027 set, and it is not where you would look for it.
The Trap: Interstitial Did Not Come From Other
The natural assumption is that all sixteen new codes were carved out of the O00.8- other ectopic bucket. Three of the four families were. Interstitial was not.
| New code | Description | Previously coded to |
|---|---|---|
| O00.121 | Right interstitial ectopic pregnancy without intrauterine pregnancy | O00.101 |
| O00.122 | Left interstitial ectopic pregnancy without intrauterine pregnancy | O00.102 |
| O00.129 | Unspecified interstitial ectopic pregnancy without intrauterine pregnancy | O00.109 |
| O00.131 | Right interstitial ectopic pregnancy with intrauterine pregnancy | O00.111 |
| O00.132 | Left interstitial ectopic pregnancy with intrauterine pregnancy | O00.112 |
| O00.139 | Unspecified interstitial ectopic pregnancy with intrauterine pregnancy | O00.119 |
Every interstitial code descends from a tubal code, matched right for right and left for left. That is anatomically coherent: the interstitial segment is the part of the fallopian tube running through the uterine wall, so an interstitial pregnancy was reasonably coded as tubal.
The consequence for anyone working backwards is direct. If you are reviewing historical records, auditing, or building a report on interstitial pregnancies, the old data is inside the tubal codes, not inside O00.8-. Searching the other-ectopic bucket for them returns nothing.
The Other Ten Came From Where You Expect
| New code | Description | From |
|---|---|---|
| O00.31 | Cesarean scar ectopic pregnancy without intrauterine pregnancy | O00.80 |
| O00.32 | Cesarean scar ectopic pregnancy with intrauterine pregnancy | O00.81 |
| O00.41 | Cervical ectopic pregnancy without intrauterine pregnancy | O00.80 |
| O00.42 | Cervical ectopic pregnancy with intrauterine pregnancy | O00.81 |
| O00.511 / .512 / .519 | Right / left / unspecified cornual ectopic pregnancy without intrauterine pregnancy | O00.80 |
| O00.521 / .522 / .529 | Right / left / unspecified cornual ectopic pregnancy with intrauterine pregnancy | O00.81 |
Note the pattern in the fifth character across the whole category: an odd digit means without an intrauterine pregnancy and an even digit means with one. O00.31 is without, O00.32 is with. That distinction is not cosmetic. A heterotopic pregnancy, ectopic and intrauterine together, is managed entirely differently from an ectopic alone, and the code carries it.
Why Cesarean Scar Mattered Enough to Get a Code
Cesarean scar ectopic pregnancy is an implantation within the scar of a previous cesarean. It is the one on this list whose incidence tracks something that has been rising for decades, which is the cesarean rate, and it carries a distinct risk profile including uterine rupture and severe haemorrhage.
Until now every one of these was reported as other ectopic pregnancy, indistinguishable in claims data from any other unusual implantation site. There was no way to count them, no way to study outcomes at scale, and no way for a payer or a registry to identify the cohort. From October 1 there is.
Cornual and Interstitial Are Not Synonyms Here
The two terms are used loosely in clinical writing and sometimes interchangeably. The code set now treats them as different, giving interstitial its own subcategory under O00.1- and cornual its own at O00.5-.
That is a documentation problem before it is a coding one. If an operative note or ultrasound report uses one word and the coder picks the matching code, the record is internally consistent. Where a note uses both terms for the same pregnancy, or uses one loosely, the safest route is a query rather than a guess, because the two now land in different places in the data and their predecessors differ too: interstitial came from tubal, cornual came from other.
What Did Not Change
Nothing in O00 was deleted. The full category still carries abdominal at O00.0-, tubal at O00.10- and O00.11-, ovarian at O00.20- and O00.21-, other at O00.80 and O00.81, and unspecified at O00.90 and O00.91.
O00.80 and O00.81 remain correct for an ectopic implantation at a site that genuinely is not one of the named ones. They are simply carrying far less than they used to.
What to Check Before You Bill
- Check the date of service. These codes are invalid on or before September 30, 2026. A September ectopic billed in October still uses the old code.
- Read the fifth character before you submit. Odd is without an intrauterine pregnancy, even is with. Getting this wrong misreports a heterotopic pregnancy.
- Look for laterality on interstitial and cornual. Both have right, left and unspecified. Tubal already did, so the documentation habit usually exists.
- Search tubal, not other, for historical interstitial cases. This is the one that will waste an afternoon otherwise.
- Query genuinely ambiguous cornual versus interstitial documentation. They are different codes from different predecessors now.
- Do not retire O00.80 and O00.81. They remain the correct codes for other sites.
Common Questions
What is the ICD-10 code for cesarean scar ectopic pregnancy?
O00.31 without an intrauterine pregnancy, or O00.32 with one, for dates of service on or after October 1, 2026. Both came from O00.80 and O00.81.
What was interstitial ectopic pregnancy coded to before?
The tubal codes O00.101, O00.102 and O00.109 without an intrauterine pregnancy, and O00.111, O00.112 and O00.119 with one, matched on side.
What does the fifth character mean?
Across this category an odd digit indicates without an intrauterine pregnancy and an even digit indicates with one.
Is cornual the same as interstitial?
Not in the code set. Interstitial is O00.12- and O00.13-; cornual is O00.51- and O00.52-. Where documentation is ambiguous, query it.
Were any O00 codes deleted?
No. All sixteen are additions, and every previously existing code in the category remains valid.
Sources and Methodology
The sixteen new codes and their descriptors were read from the FY 2027 ICD-10-CM code descriptions file published by CMS and the CDC National Center for Health Statistics, and the complete O00 category was compared between the FY 2026 and FY 2027 files to confirm that nothing was deleted. Every predecessor quoted above, including the tubal origin of the interstitial codes, is as published in the NCHS ICD-10-CM Conversion Table FY 2027, which names the previously assigned code equivalent for each new code. All files are free and none is licence gated. The complete FY 2027 deletion list is in our guide to all 30 deleted codes.
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