2021 ICD-10-CM Code O16.9

Unspecified maternal hypertension, unspecified trimester

Version 2021
Replaced Code
Billable Code
Unspecified Code
Maternity Diagnoses
Diagnoses For Females Only
MS-DRG Mapping

Valid for Submission

O16.9 is a billable diagnosis code used to specify a medical diagnosis of unspecified maternal hypertension, unspecified trimester. The code O16.9 is valid during the fiscal year 2021 from October 01, 2020 through September 30, 2021 for the submission of HIPAA-covered transactions.

The ICD-10-CM code O16.9 might also be used to specify conditions or terms like chronic hypertension complicating and/or reason for care during pregnancy, chronic hypertension in obstetric context, essential hypertension in obstetric context, hypertension and/or vomiting complicating pregnancy childbirth and/or puerperium, hypertension complicating pregnancy , hypertension complicating pregnancy, childbirth and the puerperium, etc.

The code O16.9 is applicable to female patients aged 12 through 55 years inclusive. It is clinically and virtually impossible to use this code on a non-female patient outside the stated age range.

Unspecified diagnosis codes like O16.9 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

ICD-10:O16.9
Short Description:Unspecified maternal hypertension, unspecified trimester
Long Description:Unspecified maternal hypertension, unspecified trimester

Code Classification

Replaced Code

This code was replaced in the 2021 ICD-10 code set with the code(s) listed below. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2020. This code was replaced for the FY 2021 (October 1, 2020 - September 30, 2021).


  • O16.4 - Unspecified maternal hypertension, complicating childbirth
  • O16.4 - Unspecified maternal hypertension, complicating childbirth
  • O16.5 - Unspecified maternal hypertension, comp the puerperium
  • O16.5 - Unspecified maternal hypertension, comp the puerperium

Code Edits

The Medicare Code Editor (MCE) detects and reports errors in the coding of claims data. The following ICD-10 Code Edits are applicable to this code:

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

Convert O16.9 to ICD-9 Code

The General Equivalency Mapping (GEM) crosswalk indicates an approximate mapping between the ICD-10 code O16.9 its ICD-9 equivalent. The approximate mapping means there is not an exact match between the ICD-10 code and the ICD-9 code and the mapped code is not a precise representation of the original code.

Information for Patients


High Blood Pressure in Pregnancy

What is high blood pressure in pregnancy?

Blood pressure is the force of your blood pushing against the walls of your arteries as your heart pumps blood. High blood pressure, or hypertension, is when this force against your artery walls is too high. There are different types of high blood pressure in pregnancy:

What causes preeclampsia?

The cause of preeclampsia is not known.

Who is at risk for preeclampsia?

You are at higher risk of preeclampsia if you

What problems can preeclampsia cause?

Preeclampsia can cause

What are the symptoms of preeclampsia?

Possible symptoms of preeclampsia include


[Learn More in MedlinePlus]

Code History

  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016 (First year ICD-10-CM implemented into the HIPAA code set)