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ICD-10-CM P23.1: Congenital pneumonia due to Chlamydia

P23.1 is the billable ICD-10-CM code for congenital pneumonia due to Chlamydia, in category P23 (Congenital pneumonia) of the Respiratory and cardiovascular disorders specific to the perinatal period section. As a principal diagnosis it groups to MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period). As a secondary diagnosis it is an MCC, excluded with 68 principal diagnoses.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
P23.1
billable FY2027 ICD-10-CM code
Category
P23 Congenital pneumonia
Chapter
16: Certain conditions originating in the perinatal period (P00-P96)
CC/MCC (MS-DRG v44)
MCC
CMS-HCC V28
Not mapped
POA reporting
Required

Tabular list notes for P23.1

The tabular list has no notes on P23.1 itself; the notes below apply from its parent headings.

Inherited from P23 (Congenital pneumonia)

Includes
  • infective pneumonia acquired in utero or during birth
Excludes1 (never coded together)
  • neonatal pneumonia resulting from aspiration (P24.-)

MS-DRG grouping when P23.1 is the principal diagnosis

MS-DRG v44 groups for P23.1 as principal diagnosis
MDCMS-DRGs
15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period791793

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for P23.1 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, P23.1 is an MCC under MS-DRG v44, unless the principal diagnosis is one of the 68 codes in its exclusion list. Check P23.1 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.

CMS-HCC V28 risk adjustment

P23.1 does not map to a payment HCC in the PY2027 CMS-HCC V28 model, so on its own it does not change a Medicare Advantage risk score.

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Frequently asked questions

What does ICD-10-CM P23.1 mean?

P23.1 means congenital pneumonia due to Chlamydia. It is one of 9 billable codes under P23, congenital pneumonia.

What can't be coded with P23.1?

Excludes1 at P23: neonatal pneumonia resulting from aspiration (P24.-). These are never reported together with P23.1.

Which MS-DRG does P23.1 group to?

As the principal diagnosis, P23.1 groups to MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Is P23.1 a CC or MCC?

P23.1 is an MCC under MS-DRG v44; 68 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.