2027 ICD-10-CM Diagnosis Code P77.1Stage 1 necrotizing enterocolitis in newborn
ICD-10-CM Codes›P00–P96›P76-P78›P77
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 78
- Not Chronic
P77.1 is a billable ICD-10-CM diagnosis code for stage 1 necrotizing enterocolitis in newborn. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 36 closely related codes. Coders also document this condition as fetal and/or neonatal necrotizing enterocolitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neonatal digestive and feeding disorders.
For Medicare Advantage risk adjustment, P77.1 maps to CMS-HCC Category 78 (Intestinal Obstruction/Perforation) under the V28 model, adding a risk factor of about 0.326 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
P77.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Fetal and/or neonatal necrotizing enterocolitis
- Necrotizing enterocolitis of newborn, stage 1A
- Necrotizing enterocolitis of newborn, stage 1B
- Neonatal necrotizing enterocolitis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to P77.1: its own notes plus those printed at Chapter 16. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- conditions that have their origin in the fetal or perinatal period (before birth through the first 28 days after birth) even if morbidity occurs later
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Necrotizing enterocolitis without pneumatosis, without perforation
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Notes
General instructions on how these codes are used.
- Codes from this chapter are for use on newborn records only, never on maternal records
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name P77.1, its category, or a range that includes it.
Excludes1 2
These codes carry an Excludes1 note naming P77.1: they are not reported together with it, unless the two conditions are unrelated.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Enterocolitis See Also: Enteritis; K52.9
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Premature Babies
Almost 1 of every 10 infants born in the United States are premature, or preemies. A premature birth is when a baby is born before 37 completed weeks of pregnancy. A full-term pregnancy is 40 weeks.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert P77.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About P77.1Overview
What is the ICD-10 code for stage 1 necrotizing enterocolitis in newborn?
The ICD-10-CM code for stage 1 necrotizing enterocolitis in newborn is P77.1 (sometimes written as P771). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is P77.1 (Necrotizing enterocolitis of newborn) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report stage 1 necrotizing enterocolitis in newborn on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does P77.1 group to?
When stage 1 necrotizing enterocolitis in newborn is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, with relative weights from 4.1073 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.
Is P77.1 a CC or MCC?
CMS lists P77.1 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 36 closely related codes in its exclusion list.
What is the ICD-9 equivalent of P77.1?
Under the General Equivalence Mappings, stage 1 necrotizing enterocolitis in newborn converts to ICD-9-CM 777.51 (stg I nec enterocol NB). The mapping is a direct match.
What HCC is P77.1?
P77.1 (stage 1 necrotizing enterocolitis in newborn) maps to CMS-HCC Category 78 (Intestinal Obstruction/Perforation), commonly written as HCC 78, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It does not map to any RxHCC in the Part D prescription drug model.
Does P77.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, P77.1 adds a risk adjustment factor of about 0.326 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.326 to 0.688 depending on the payment segment). A more severe related category (HCC 77) supersedes it when both are reported. See the full factor table on the HCC 78 category page.
