Neonatal Abstinence Syndrome (NAS) Among Newborn Hospitalizations

Newborn hospitalizations involving neonatal abstinence syndrome (NAS) require that the discharge record includes both of the following:

• A diagnosis of NAS
• A diagnosis of in-hospital birth or a birth before admission to the hospital, either in this case resulting in a newborn hospitalization. Eligible cases only exist on the initial hospitalization related to the birth and not subsequent hospital admissions during the neonatal period.

The coding for NAS and birth is identified by any diagnosis (all-listed) in the following ranges of ICD-10-CM¹ and ICD-9-CM² codes:

ICD-10-CM Codes Starting October 1, 2015

To identify NAS under ICD-10-CM, the birth record must include any diagnosis of:

• P96.1: Neonatal withdrawal symptoms from maternal use of drugs of addiction

Note that a diagnosis of P04.14 (Newborn affected by maternal use of opiates), which was a valid ICD-10-CM code as of October 1, 2018, was initially included in the definition of NAS when statistics were previously updated to include 2018 data for some States. However, this code has since been dropped because it does not necessarily reflect the definition of NAS (newborns exhibiting withdrawal symptoms as a result of prenatal opioid exposure), and 2018 statistics have been updated accordingly.

Birth records under ICD-10-CM are identified by any diagnosis of:

• Z38 Series: Liveborn infants according to place of birth and type of delivery

ICD-9-CM Codes Prior to October 1, 2015

To identify NAS under ICD-9-CM, the birth record must include any diagnosis of:

• 779.5: Drug withdrawal syndrome in newborn

Birth records under ICD-9-CM are identified by any diagnosis of:

• V30-V39 Series: Liveborn infants according to type of birth
• Ending in 00 or 01: Indication of birth inside hospital
• Ending in 1: Indication of birth before admission to hospital.

Excluded Codes

It should be noted that under ICD-9-CM, the identification of NAS must not include an indication of a possible iatrogenic case, which is defined by ICD-9-CM diagnosis codes of 765.00-765.05, 770.7, 772.10-772.14, 777.50-777.53, 777.6, and 779.7. Similar exclusions are not necessary under ICD-10-CM because iatrogenic cases would be reported under a different ICD-10-CM diagnosis code (P96.2: Withdrawal symptoms from therapeutic use of drugs in newborn), which is not included in the ICD-10-CM definition of NAS.

Records under ICD-9-CM that indicate a birth outside a hospital with the infant not being hospitalized are not included.

Specific to Missouri, the Missouri Hospital Association (MHA) published a policy brief in 2018 (http://www.mhanet.com/mhaimages/advocacy/PolicyBrief_Preventing_NAS_0618.pdf ) that focuses on the prevalence of NAS in the state. This report defines rates of NAS using the ICD-10-CM diagnosis code P96.2 (withdrawal symptoms from therapeutic use of drugs in newborn) in addition to the code P96.1 (neonatal withdrawal symptoms from maternal use of drugs of addiction) that is used to identify NAS hospitalizations in HCUP Fast Stats. As a result, the NAS rates reported in Fast Stats for Missouri may be lower than NAS rates reported by MHA.

¹ International Classification of Diseases, Tenth Revision, Clinical Modification/Procedure Coding System
² International Classification of Diseases, Ninth Revision, Clinical Modification

Newborn Hospitalizations (Inpatient)

State-level statistics on newborn hospitalizations are drawn from the HCUP State Inpatient Databases (SID). The SID are limited to patients treated in community hospitals in the State. Community hospitals are defined as short-term, non-Federal, general, and other hospitals, excluding hospital units of other institutions (e.g., prisons). Included among community hospitals are obstetrics and gynecology, otolaryngology, orthopedic, cancer, pediatric, public, and academic medical hospitals. Excluded are community hospitals that are also long-term care facilities such as rehabilitation, psychiatric, and alcoholism and chemical dependency hospitals.

State-level statistics are based on the hospital State and not the patient resident State. This means that State-level statistics include all newborn hospitalizations in the State’s community hospitals—newborn hospitalizations among in-State residents and newborn hospitalizations by residents of other States. State-level statistics do not include newborn hospitalizations by in-State residents that occurred at hospitals in other States. Thus, the statistics reported here may differ from other NAS-related statistics that are based on the State of the patient’s residence.

We adjust the discharge counts for hospitals that were not included in the SID or quarterly data. Across all States, the SID are missing about 7 percent of community hospitals and about 1.5 percent of discharges. Weighting for missing hospitals uses the following information from the American Hospital Association (AHA) Annual Survey of Hospitals to define strata within the State:

• Ownership: government, private nonprofit, and private investor-owned
• Size of the hospital based on the number of beds: small, medium, and large categories defined within region
• Location combined with teaching status: rural, urban nonteaching, urban teaching

If a stratum is missing one or more hospitals in the State data, then we set the discharge weight to the total number of discharges reported in the AHA divided by the total number of discharges in the State data. If all hospitals in a stratum are represented in the State data, then we set the discharge weight to 1. We also adjust the discharge weights for hospitals that have missing discharge quarters of data, provided there is no indication in the AHA Annual Survey that the facility had closed.

Discharge weights are specific to the data year for SID through 2017 (e.g., discharge weights for the 2017 SID use 2017 AHA data). Weighting for HCUP data starting in 2018 is based on AHA data from the prior year because current information is often unavailable (e.g., discharge weights for the 2018 SID use 2017 AHA data).

National statistics on newborn hospitalizations are drawn from the HCUP National (Nationwide) Inpatient Sample (NIS). The NIS is sampled from the HCUP State Inpatient Databases (SID). Beginning with the 2012 data year, the NIS is a 20 percent sample of discharges from community hospitals, excluding rehabilitation and long-term acute care (LTAC) hospitals that participate in HCUP in the corresponding data year. For data years 1988 through 2011, the NIS was a 20 percent sample of community, nonrehabilitation hospitals and included all discharges from sampled hospitals. The national estimates on newborn hospitalizations were developed using the NIS Trend Weight Files for consistent estimates across all data years (e.g., LTACs were removed from earlier data years using trend weights).

The number of years of data reported for each individual State and the United States depends on the availability of the corresponding HCUP database. For example, the HCUP nationwide databases for the most recent data year can only be created after all of the necessary State databases are available. State-level data are included in Fast Stats when they become available. It is possible for a State's annual SID to be updated. As a result, previously reported statistics for a given State may change.

Counts in this section of Fast Stats are un-rounded with any counts less than or equal to 10 suppressed for confidentiality. This will cause a discontinuity in the trend lines displayed in the figures.

Specific to Colorado, the number of newborn hospitalizations for babies born to mothers covered by Medicaid may be an undercount because of sporadic reporting of the normal newborn births with the mother's delivery record, instead of a separate newborn hospitalization. This results in NAS rates, particularly for Medicaid, being somewhat higher.

Unit of Analysis

The unit of analysis is the newborn hospitalization (i.e., birth inside hospital or prior to hospital admission), not a person or patient.

Clinical Coding

On October 1, 2015, the United States transitioned from ICD-9-CM to ICD-10-CM. The graphs demarcate this transition with statistics reported using ICD-9-CM coding identified as "ICD-9-CM" on the graphs and statistics reported using ICD-10-CM coding identified as "ICD-10-CM" on the graphs. The 2015 rates of NAS per 1,000 newborn hospitalizations and statistics for costs and length of stay are based on three quarters of data with ICD-9-CM codes only (January 1, 2015 to September 30, 2015). The number of NAS newborn hospitalizations in 2015 is not reported because the statistics are not based on full year data. Users may observe discontinuity in trends between NAS records defined by ICD-9-CM coding (ending in 2015) and ICD-10-CM coding (starting in 2016). More information on the impact of ICD-10-CM/PCS is available on the HCUP User Support (HCUP-US) web page for ICD-10-CM/PCS Resources.

Rate per 1,000 Newborn Hospitalizations

Rates per 1,000 newborn hospitalizations are presented overall and by sex, expected payer, community-level income, and patient location. The rate includes the HCUP number of NAS-related newborn hospitalizations in the numerator and the total number of newborn hospitalizations in the denominator (with a multiplier of 1,000). The denominator is consistently defined with the numerator (e.g., rates for females use NAS and newborn hospitalization counts specific to females).

Rates are suppressed for confidentiality when the denominator is less than or equal to 25.

Cost per Stay (Median)

Costs are calculated using Cost-to-Charge Ratios (CCR), which are specific to each hospital as opposed to individual types of care. The cost per stay is presented as a median value rounded to the nearest hundred. The median cost is not an average but rather represents the cost that occurs at the midpoint of the ordered distribution of all observed costs. The cost per stay is presented for NAS newborn hospitalizations overall compared with that of other newborn hospitalizations that do not include a diagnosis of NAS.

The SID and NIS include information on total hospital charges for a newborn hospitalization. Charges represent the amount a hospital billed for the entire hospital stay, excluding professional (physician) fees. Total hospital charges are converted to costs using HCUP Cost-to-Charge Ratios (CCRs) based on hospital accounting reports from the Centers for Medicare & Medicaid Services (CMS). Costs reflect the actual expenses incurred in the production of hospital services, such as wages, supplies, and utility costs. For each hospital in the NIS, a hospital-wide cost-to-charge ratio is used. The median cost per stay is calculated using newborn hospitalizations with nonmissing total costs. Costs are not imputed if total charges are not reported on the discharge record. Costs for the most recent data year will not be presented if the HCUP CCRs for that data year are not yet available.

The cost per stay is suppressed when the numerator is less than or equal to 10.

Inflation-Adjusted Cost per Stay (Median)

The inflation-adjusted cost per stay is presented as a median value rounded to the nearest hundred. The median inflation-adjusted cost is not an average but rather represents the cost that occurs at the midpoint of the ordered distribution of all observed costs. The inflation-adjusted cost per stay is presented for NAS newborn hospitalizations overall compared with that of other newborn hospitalizations that do not include a diagnosis of NAS.

The median cost per stay is inflation adjusted using price indexes for the Gross Domestic Product (GDP) from the U.S. Department of Commerce Bureau of Economic Analysis (BEA). We used the BEA Interactive Data query tool to request National Data, GDP & Personal Income, Section 1 Domestic Product and Income, Table 1.1.4. Price Indexes for Gross Domestic Product. Price indexes for data years 2008-2014 were obtained on June 23, 2015. Price indexes for subsequent data years were obtained at later dates to coincide with updates to this section of Fast Stats. The adjustment used 2010 as the index base so that updates to the trends could retain a consistent base.

The inflation-adjusted cost per stay is suppressed when the numerator is less than or equal to 10.

Median Length of Stay

The length of stay (LOS) is presented as a median value. The median LOS is not an average but rather represents the LOS that occurs at the midpoint of the ordered distribution of all observed LOS values. The LOS is presented for NAS newborn hospitalizations overall compared with that of other newborn hospitalizations that do not include a diagnosis of NAS.

LOS is the number of days that the patient stayed in the hospital. It is calculated by subtracting the admission date from the discharge date. Same-day stays are therefore coded with a length of stay of 0. The median LOS is calculated using newborn hospitalizations with nonmissing LOS.

LOS is suppressed when the numerator is less than or equal to 10.

Sex

All nonmale, nonfemale responses are set to missing. Newborn hospitalizations with missing values for sex are excluded from results reported by sex.

Expected Payer

The "expected payer" data element in HCUP databases provides information on the type of payer that the hospital expects to be the source of payment for the hospital bill. Trends in NAS among newborn hospitalizations by expected payer are presented by the following categories: Medicaid, private insurance, and self-pay/no charge. Information by Medicare, other, missing, or invalid are not included in the reporting by expected payer. The distribution of cases in the excluded payer categories is provided below. Please note that all other reporting of NAS rates, counts, cost, and length of stay include all payer types.

• In the 2018 National Inpatient Sample (NIS), the percentages of NAS-related newborn hospitalizations that are not presented by expected payer are: 1.1% for Other, 0.2% for Medicare, and 0.2% for missing or invalid. The corresponding percentages of all newborn hospitalizations are: 2.6% for Other, 0.3% for Medicare, and 0.2% for missing or invalid.
• In the 2018 States Inpatient Databases (SID):
• The percentages of NAS-related newborn hospitalizations that are not presented by expected payer are: an average of 1.0% for Other (range of 0.0% to 5.4% across States), 0.2% for Medicare (range of 0.0% to 4.0% across States), and 0.4% for missing or invalid (range of 0.0% to 13.5% across States).
• The corresponding percentages of all newborn hospitalizations by expected payer are: an average of 3.2% for Other (range of 0.8% to 18.7% across States), 0.2% for Medicare (range of 0.0% to 3.1% across States), and 0.3% for missing or invalid (range of 0.0% to 5.2% across States).

Self-pay/no charge newborn hospitalizations include records that have an expected primary payer of self-pay, no charge, charity, or no expected payment. The self-pay/no charge records may also include those with an expected payer of Indian Health Services, county indigent, migrant health programs, Ryan White Act, Hill-Burton Free Care, or other Federal, State, and local programs for the indigent when those programs are identifiable in the Partner-provided coding of expected payer. This reclassification of patients is only possible for some States and not for national estimates. More information on identifying programs reported in HCUP data that may cover the self-pay/no charge category is available in HCUP Methods Series Reports by Topic "User Guide - An Examination of Expected Payer Coding in HCUP Databases" (multiple documents; updated annually).

Community-Level Income

Community-level income is based on the median household income of the patient's ZIP Code of residence. Quartiles are defined so that the total U.S. population is evenly distributed across four groups. The cut-offs for the quartile designation are determined annually using ZIP Code demographic data obtained from Claritas, a vendor that produces population estimates and projections based on data from the U.S. Census Bureau. Claritas estimates intercensal annual household and demographic statistics for geographic areas. The value ranges for the national income quartiles vary by year. Income quartile is missing if the patient is homeless or foreign. Newborn hospitalizations missing the income quartile are excluded from results reported by community-level income.

Patient Location

Patient location is based on the six-category, county-level scheme developed by the National Center for Health Statistics (NCHS) to study the relationship between urbanization and health:

• Large central metropolitan: Counties in metropolitan statistical areas (MSAs) of 1 million or more population that contain the entire population of the largest principal city of the MSA, have their entire population contained in the largest principal city of the MSA, or contain at least 250,000 inhabitants of any principal city of the MSA
• Large fringe metropolitan (suburbs): Counties in MSAs of 1 million or more population that did not qualify as large central metropolitan counties
• Medium metropolitan: Counties in MSAs of populations of 250,000 to 999,999
• Small metropolitan: Counties in MSAs of population less than 250,000
• Micropolitan: Counties in micropolitan statistical areas
• Noncore: Nonmetropolitan counties that did not qualify as micropolitan

The micropolitan and noncore categories are combined into a single category (“Rural”) in order to preserve results when cell sizes are too small. For rates prior to 2014, the NCHS classification is based on population density from the 2000 Census. Starting in 2014, the NCHS classification is based on population density from the 2010 Census. Newborn hospitalizations missing patient location are excluded from results reported by patient location.

Patient location categories may include out-of-state patients because the classification is based on patient residence county but reported by the State for the hospital. Additional information on the patient location classification system is available at NCHS Urban-Rural Classification Scheme for Counties.

Interactive Map

The interactive map of NAS among newborn hospitalizations provides annual rates of NAS per 1,000 newborn hospitalizations. States are color-coded to identify each State's NAS-related inpatient rate relative to the distribution across all States providing 2016 data. States are classified into one of five categories based on the distribution of rates in 2016: lowest 20 percent, 2nd lowest 20 percent, middle 20 percent, 2nd highest 20 percent, highest 20 percent. States in grey do not have data available; this may include States that are not currently HCUP Partners, are not participating in Fast Stats, or participate but have not provided data for the year displayed. (Note: prior to the August 2020 update to this topic, the quintiles were based on a distribution of States that provided 2015 data.)