Pediatric Hospital Readmissions for Infants With Neonatal Opioid Withdrawal Syndrome, 2016-2019

Advances in animal models of prenatal opioid exposure

Neonatal opioid withdrawal syndrome (NOWS) is a growing public health concern. The complexity of in utero opioid exposure in clinical studies makes it difficult to investigate underlying mechanisms that could ultimately inform early diagnosis and treatments. Clinical studies are unable to dissociate the influence of maternal polypharmacy or the environment from direct effects of in utero opioid exposure, highlighting the need for effective animal models. Early animal models of prenatal opioid exposure primarily used the prototypical opioid, morphine, and opioid exposure that was often limited to a narrow period during gestation. In recent years, the number of preclinical studies has grown rapidly. Newer models utilize both prescription and nonprescription opioids and vary the onset and duration of opioid exposure. In this review, we summarize novel prenatal opioid exposure models developed in recent years and attempt to reconcile results between studies while critically identifying gaps within the current literature.

A case-control study comparing rates and diagnoses of hospital readmission in infants affected by neonatal abstinence syndrome

OBJECTIVE

Rates of neonatal abstinence syndrome/neonatal opioid withdrawal syndrome (NAS/NOWS), a withdrawal syndrome from opioids and other substances resulting from intrauterine exposure, have been increasing exponentially in the U.S. To improve health outcomes, it is important to understand population health risks, including rehospitalization and related diagnoses, using current data. This study will compare and describe the rates of rehospitalization, the demographic characteristics and the rehospitalization diagnoses and age at diagnosis between the infants affected by NAS/NOWS to those sampled who were unaffected. This study will also describe the frequency of NAS/NOWS births per year along with a yearly comparison of readmissions in those affected by NAS/NOWS to those who were not (2016-2020).

METHODS

Health claims data were used to conduct a case/control study. Diagnosis codes for neonatal withdrawal syndrome/NAS/NOWS (P04.49 or P96.1 and P96.1 alone) from 1 October 2015 to 1 June 2021 were extracted, and controls were case-matched based on month/year of birth. Rehospitalizations following birth and the related diagnoses were described and grouped using the Agency of Healthcare Research Quality Clinical Classifications Software Refined Frequency distribution. The chi-square test of association and generalized estimating equation modeling were used for data analysis.

RESULTS

Infants affected by NAS/NOWS are 2.7 times more likely to have a rehospitalization. White, non-Hispanic neonates (OR = 1.5; p = .007) and those infants residing in rural areas (OR = 1.9; p < .001) were disproportionately affected. We identified a host of admission diagnoses with increased prevalence in infants affected by NAS/NOWS when compared to those who were not affected (e.g. infectious diseases, feeding disorders).

CONCLUSIONS

Infants with NAS/NOWS are at increased risk of rehospitalization with a host of diagnoses, and specific demographic groups (White, rural) are more highly affected.

A mini review of what matters in the management of NAS, is ESC the best care?

As the use of opioids and polysubstance by pregnant women has increased over the years, there has also been a sharp increase in cases of neonatal abstinence syndrome (NAS). Classically, infants affected by NAS have been cared for in neonatal intensive care units resulting in an increase of healthcare expenditure and resource utilization as well as separation from the families. Consequently, the Eat, Sleep, and Console (ESC) tool was developed and promoted as a novel method that focuses on maternal/infant dyad during hospital stay while decreasing the use of pharmacological interventions and therefore decreasing the length of stay and healthcare expenditure. Thus, it has been implemented in several hospitals in the United States. Although the training of staff has been proposed and the interventions of sleep, eat, and console are defined, there still exists a lack of standardization of this practice specifically in regard to the type of associated non-pharmacological practices as well as the reports of its short- and long-term outcomes.

Maternal Opioid Use Disorder and the Risk of Postneonatal Infant Mortality

Importance

The risk of serious long-term outcomes for infants born to individuals with opioid use disorder (OUD) is not fully characterized, nor is it well understood whether risks are modified by infant diagnosis of neonatal opioid withdrawal syndrome (NOWS).

Objective

To characterize the risk of postneonatal infant mortality among infants with a NOWS diagnosis or born to individuals with OUD.

Design, Setting, and Participants

The study team conducted a retrospective cohort study of 390 075 infants born from 2007 through 2018 to mothers who were enrolled in Tennessee Medicaid from 183 days prior to delivery through 28 days post partum (baseline). Maternal and infant baseline characteristics were measured using administrative claims and birth certificates, and infants were followed up from day 29 post partum through day 365 or death. Deaths were identified using linked death certificates through 2019. These data were analyzed from February 10, 2022, through March 3, 2023.

Exposure

Infant exposures included birth to an individual with OUD or postnatal diagnosis of NOWS. The study team defined a pregnant individual's OUD status (maternal OUD) as having OUD diagnosis or a maintenance medication prescription fill during baseline; this study defined NOWS as having NOWS diagnosis up to day 28. Groups were categorized by exposures as maternal OUD with NOWS (OUD positive/NOWS positive), maternal OUD without NOWS (OUD positive/NOWS negative), no documented maternal OUD with NOWS (OUD negative/NOWS positive), and no documented maternal OUD or NOWS (OUD negative/NOWS negative, unexposed).

Main Outcome and Measures

The outcome was postneonatal infant death, confirmed by death certificates. Cox proportional hazards models were used, adjusting for baseline maternal and infant characteristics, to estimate adjusted hazard ratios (aHRs) and 95% CIs for the association between maternal OUD or NOWS diagnosis with postneonatal death.

Results

Pregnant individuals in the cohort had a mean (SD) age of 24.5 (5.2) years; 51% of infants were male. The study team observed 1317 postneonatal infant deaths and incidence rates of 3.47 (OUD negative/NOWS negative, 375 718), 8.41 (OUD positive/NOWS positive, 4922); 8.95 (OUD positive/NOWS negative, 7196), and 9.25 (OUD negative/NOWS positive, 2239) per 1000 person-years. After adjustment, the risk of postneonatal death was elevated for all groups, relative to the unexposed: OUD positive/NOWS positive (aHR, 1.54; 95% CI, 1.07-2.21), OUD positive/NOWS negative (aHR, 1.62; 95% CI, 1.21-2.17), and OUD negative/NOWS positive (aHR, 1.64; 95% CI, 1.02-2.65).

Conclusions and Relevance

Infants born to individuals with OUD or with a NOWS diagnosis had an increased risk of postneonatal infant mortality. Future work is necessary to create and evaluate supportive interventions for individuals with OUD during and after pregnancy to reduce adverse outcomes.

Association between pharmacologic treatment and hospital utilization at birth among neonatal opioid withdrawal syndrome mother-infant dyads

OBJECTIVE

We linked mother-baby dyads to explore associations between maternal medication-assisted therapy (MAT) and infants' pharmacologic treatment on birth hospital utilization for infants with NOWS.

METHODS

We extracted singleton infant and maternal delivery discharges from PHIS hospitals with large volumes of deliveries for 2016-2019. We matched newborns with NOWS to maternal delivery discharges by hospital, day of birth, mode of delivery, and ZIP code. We examined the association between maternal MAT, infants' pharmacologic treatment, and hospital utilization at birth.

RESULTS

We included N = 146 mother-baby dyads from six hospitals (74% match rate). Among matched dyads, 51% received maternal MAT, 60% pharmacotherapy (37% both). Infants treated non-pharmacologically and born to mothers receiving MAT had the shortest stays vs. infants without pharmacotherapy or MAT (RR = 0.29; 95% CI: 0.25-0.35).

CONCLUSIONS

These findings underscore the importance of adequate perinatal treatment for opioid use disorder to improve outcomes for mothers and infants with opioid exposure.

Neonatal Opioid Withdrawal Syndrome: An Update on Developmental Outcomes

Infants and children with prenatal opioid exposure generally have development within the normal range; however, they seem to be at risk for behavioral problems and for lower scores on cognitive, language, and motor assessments than children without prenatal opioid exposure. It is as of yet unclear whether prenatal opioid exposure itself causes issues with development and behavior, or whether it is simply correlated, due to other confounding factors.

A Comparison of Methods Examining Time-to-Readmission in the First Year of Life

BACKGROUND AND OBJECTIVES

Readmissions analyses typically calculate time-to-readmission relative to hospital discharge. For newborns, this definition can be challenging when comparing groups with disparate birth stays. We compare 2 approaches to calculate readmissions and examine 1 year readmissions for newborns with versus without neonatal opioid withdrawal syndrome (NOWS; mean length of stay = 17 vs 2 days).

METHODS

Using birth discharge data from the Pediatric Health Information System (PHIS), we compared crude and adjusted 1 year readmissions by NOWS diagnosis using Cox regression models predicting time-to-readmission from: (1) birth discharge; and (2) birth (day-of-life), with left truncation allowing for delayed entry into the at-risk period at birth discharge.

RESULTS

We included N = 155 885 birth discharges (n = 1467 with NOWS). At 1 year, 10% of infants with NOWS versus 6% without had been readmitted. Readmission risk was highest within 1 week since discharge or birth for newborns without NOWS, whereas those with NOWS were at higher risk later into infancy. NOWS was associated with a higher adjusted hazard of 1 year readmissions since discharge (adjusted hazard ratio [aHR]=1.58; 95% CI: 1.20-2.08) and a higher adjusted hazard of 1 year readmissions since birth (aHR = 1.56; 95% CI: 1.21-2.03). Estimates vary by choice of index date, particularly at early time-points, converging later into infancy.

CONCLUSIONS

Our findings underscore the importance of methodological decisions for newborn readmissions. Although results were similar at 1 year with nearly identical adjusted hazards, approaches differed substantially through the neonatal period.

Length of Stay Among Infants with Neonatal Abstinence Syndrome and Risk of Hospital Readmission

OBJECTIVES

To assess whether a shorter length of stay (LOS) is associated with a higher risk of readmission among newborns with neonatal abstinence syndrome (NAS) and examine the risk, causes, and characteristics associated with readmissions among newborns with NAS, using a longitudinally linked population-based database.

METHODS

Our study sample included full-term singletons with NAS (n = 4,547) and without NAS (n = 327,836), born in Massachusetts during 2011-2017. We used log-binomial regression models to estimate the crude risk ratios (cRRs) and adjusted RRs with 95% confidence intervals (CI) of the association between LOS and readmissions, controlling for maternal age, race/ethnicity, education, marital status, insurance, method of delivery, birthweight, adequacy of prenatal care, smoking, and abnormal conditions of newborn.

RESULTS

Compared with infants without NAS, infants with NAS had a non-significantly higher risk of readmission within 2-42 days (2.8% vs. 2.5%; p = 0.17) and a significantly higher risk of readmission within 43-182 days (2.7% vs. 1.8%; p < 0.001). The risk of readmission within 2-42 days was significantly higher among infants with NAS with a LOS of 0-6 days compared to a LOS of 14-20 days (reference group) (aRR: 2.1; 95% CI: 1.2-3.5). No significant differences in readmission rates between 43 and 182 days were observed across LOS categories.

CONCLUSIONS

Among infants with NAS, a LOS of 0-6 days was associated with a significantly higher risk of readmission within 2-42 days of discharge compared to a longer LOS.

The impact of opioid exposure during pregnancy on the human neonatal immune profile

BACKGROUND

The increasing magnitude of the opioid crisis and rising rates of neonatal abstinence syndrome (NAS) diagnoses highlight the need for increased research into how maternal substance use during pregnancy can impact the neonatal immune profile and its functionality. We hypothesized that neonates with opioid exposure would have reduced proportions of some immune cells, an anti-inflammatory cytokine profile, reduced T cell proliferation, and monocyte bacterial killing activity compared to the control population.

METHODS

The present study compares immune cell populations, inflammatory and anti-inflammatory cytokine and chemokine levels in the serum, and monocyte and T cell functional activity using umbilical cord samples from neonates with known opioid exposure during gestation and from control neonates without known exposure.

RESULTS

Our findings demonstrated a significant reduction in neutrophils, decreased levels of inflammatory cytokines in the serum, and reduced IL-2 production during in vitro CD4⁺ T cell proliferation in neonates exposed to opioids compared to controls. The neutrophil findings were supported by retrospective analysis of an extended network of deidentified patient records.

CONCLUSIONS

This study is the first of its kind to evaluate differences in neonatal immunity as a result of opioid exposure in the human population that will inform continued mechanistic studies.

IMPACT

The opioid epidemic has become a public health crisis in the United States, and the corresponding incidence of neonatal abstinence syndrome (NAS) have risen accordingly. New research is required to understand the short and long-term health impacts of opioid exposure to the neonate. This is the first human study to investigate the immunologic profile and functionality in neonates with known opioid exposure in utero. The abundance of neutrophils and the ratio of neutrophils to lymphocytes is significantly reduced along with inflammatory cytokines and chemokines following opioid exposure during pregnancy. The immune profile in opioid-exposed neonates may promote susceptibility to infection.