Male Sex Associated With Increased Risk of Neonatal Abstinence Syndrome

The role of genetics in neonatal abstinence syndrome

Neonatal Abstinence Syndrome (NAS) after in-utero exposure to opioids remains a significant public health concern. NAS is a highly variable condition in which presentation and severity cannot be explained by clinical factors alone. Research in human subjects has identified both genetic and epigenetic associations with prenatal opioid exposure and NAS severity, including single nucleotide polymorphisms, DNA methylation differences, and gene expression modifications. Animal studies have also identified key gene pathways that are likely important contributors to NAS phenotype. The clinical significance of identified genetic associations with NAS are unclear and warrant further study to see how they could impact NAS management.

The acoustic properties, syllable structure, and syllable sequences of ultrasonic vocalizations (USVs) during neonatal opioid withdrawal in FVB/N mouse substrains

Concomitant with the opioid epidemic, there has been a rise in pregnant women diagnosed with opioid use disorder and cases of infants born with neonatal opioid withdrawal syndrome (NOWS). NOWS refers to signs and symptoms following cessation of prenatal opioid exposure that comprise neurological, gastrointestinal, and autonomic system dysfunction. A critical indicator of NOWS severity is excessive, high-pitched crying. However, NOWS evaluation is, in large part, subjective, and additional cry features may not be easily recognized during clinical assessment. Thus, there is a need for more objective measures to determine NOWS severity. We used a third trimester-approximate opioid exposure paradigm to model NOWS traits in genetically similar inbred substrains of FVB/N mice (NJ, NCrl, NHsd, and NTac). Pups were injected twice daily from postnatal day 1 (P1) to P14 with morphine (10 mg/kg, s.c.) or saline (20 ml/g, s.c.). Because there were only very minor substrain differences in spontaneous withdrawal-induced ultrasonic vocalization (USV) profiles, we collapsed across substrains to evaluate the effects of morphine withdrawal on additional USV properties. We identified syllable sequences unique to morphine-withdrawn and saline-control FVB/N pups on P7 and P14. We also observed an effect of spontaneous morphine withdrawal on the acoustic properties of USVs and specific syllables on P7 and P14. Multiple withdrawal traits correlated with some acoustic properties of USVs and syllable type emission in morphine-withdrawn FVB/N pups on P7 and P14. These data provide an in-depth investigation of mouse USV syllable profiles and acoustic features during spontaneous neonatal opioid withdrawal in mice.

The ultrasonic vocalization (USV) syllable profile during neonatal opioid withdrawal and a kappa opioid receptor component to increased USV emissions in female mice

Rationale

Opioid use during pregnancy can lead to negative infant health outcomes, including neonatal opioid withdrawal syndrome (NOWS). NOWS comprises gastrointestinal, autonomic nervous system, and neurological dysfunction that manifest during spontaneous withdrawal. Variability in NOWS severity necessitates a more individualized treatment approach. Ultrasonic vocalizations (USVs) in neonatal mice are emitted in isolation as a stress response and are increased during opioid withdrawal, thus modeling a negative affective state that can be utilized to test new treatments.

Objectives

We sought to identify the behavioral and USV profile, brainstem transcriptomic adaptations, and role of kappa opioid receptors in USVs during neonatal opioid withdrawal.

Methods

We employed a third trimester-approximate opioid exposure model, where neonatal inbred FVB/NJ pups were injected twice-daily with morphine (10mg/kg, s.c.) or saline (0.9%, 20 ul/g, s.c.) from postnatal day(P) 1 to P14. This protocol induces reduced weight gain, hypothermia, thermal hyperalgesia, and increased USVs during spontaneous morphine withdrawal.

Results

On P14, there were increased USV emissions and altered USV syllables during withdrawal, including an increase in Complex 3 syllables in FVB/NJ females (but not males). Brainstem bulk mRNA sequencing revealed an upregulation of the kappa opioid receptor (Oprk1), which contributes to withdrawal-induced dysphoria. The kappa opioid receptor (KOR) antagonist, nor-BNI (30 mg/kg, s.c.), significantly reduced USVs in FVB/NJ females, but not males during spontaneous morphine withdrawal. Furthermore, the KOR agonist, U50,488h (0.625 mg/kg, s.c.), was sufficient to increase USVs on P10 (both sexes) and P14 (females only) in FVB/NJ mice.

Conclusions

We identified an elevated USV syllable, Complex 3, and a female-specific recruitment of the dynorphin/KOR system in increased USVs associated with neonatal opioid withdrawal severity.

Differences in withdrawal symptoms, microglia activity, and cognitive functioning in rats exposed to continuous low-dose heroin in-utero

INTRODUCTION

Opioid use during pregnancy and subsequent neonatal opioid withdrawal syndrome (NOWS) have been associated with poor developmental outcomes including cognitive functioning. Less is known about the underlying molecular effects of prenatal opioid exposure and subsequent withdrawal; however, given the recent increase in NOWS cases, there is a pressing need to better understand these effects, which may partially explain cognitive deficits that have been observed in both preclinical NOWS models and patients with NOWS. This study evaluated the effects of prenatal heroin exposure and subsequent precipitated withdrawal symptoms on microglial reactivity in the nucleus accumbens (NAc), dorsal hippocampus (HC), and ventral tegmental area (VTA) in rat neonates, as well as cognitive functioning at three developmental time points using the Morris Water Maze (MWM) task.

METHODS

Heroin or saline (2 mg/kg) was randomly assigned and administered to six pregnant Sprague Dawley rat dams via osmotic minipump. A total of 63 rat neonates underwent naloxone-precipitated (5 mg/kg, subcutaneous injection) withdrawal testing at postnatal day 10 (PN10). Following withdrawal testing, neonates were randomly assigned to undergo perfusion and subsequent immunohistochemistry experiments to fluoresce Iba-1 for microglia detection, or to undergo the MWM task at three separate developmental time points (PN21-23; PN37; PN60) for cognitive testing.

RESULTS

Results suggest that in-utero heroin exposure led to an increase in ultrasonic vocalizations during naloxone-precipitated withdrawal; a sensitive index of withdrawal in rat neonates. Additional results suggest increased microglial reactivity in the HC and VTA, but not the NAc, as well as reduced performance during the MWM in the group exposed to heroin in-utero.

DISCUSSION

Together, these data suggest that in-utero opioid exposure is associated with microglial reactivity in brain regions associated with learning and memory, and may be associated with later cognitive deficits. Further research is needed to characterize these findings, which may inform future therapeutic strategies for this vulnerable population.

Effects of prenatal exposure to methadone or buprenorphine and maternal separation on anxiety-like behavior in rats

BACKGROUND

The use of medications for opioid use disorder such as methadone or buprenorphine is increasing among pregnant women. However, long-term effects of this treatment on the children's health are not well understood. A key challenge is distinguishing the effects of opioid exposure from other confounding factors associated with human opioid use, such as reduced maternal care. In this study, we therefore used a multi-risk factor design to examine anxiety-like behavior in rats prenatally exposed to methadone or buprenorphine, with or without maternal separation the first two weeks after birth.

METHODS

Female Sprague Dawley rats were exposed to methadone (10mg/kg/day), buprenorphine (1mg/kg/day) or sterile water throughout gestation. Half of the offspring in each litter experienced maternal separation for 3h per day from postnatal day 2 to 12. Male and female offspring (6-9 weeks) were tested in the open field, light-dark transition and elevated plus maze tests to assess anxiety-like behavior.

RESULTS

Offspring exposed to buprenorphine and not subjected to maternal separation displayed increased anxiety-like behavior in 3 out of 6 outcomes in the light-dark transition and elevated plus maze tests. Maternal separation did not exacerbate, but rather diminished this behavior. Males and females responded differently to methadone, with a trend towards reduced anxiety for males and increased anxiety for females.

CONCLUSIONS

Prenatal exposure to methadone or buprenorphine may increase the risk of developing anxiety-like behavior later in life, but the effect depends on specific subgroup characteristics. Further research is required to draw definitive conclusions.

Inpatient Growth in Infants Requiring Pharmacologic Treatment for Neonatal Opioid Withdrawal Syndrome

Aim: To assess inpatient growth parameter trajectories and to identify the type of opioid exposure and treatment characteristics influencing growth parameters of infants admitted to the newborn intensive care unit (NICU) for pharmacological treatment of neonatal opioid withdrawal syndrome (NOWS). Methods: Charts of term infants with NOWS admitted to NICU from 2012 to 2019, who received pharmacologic treatment, were reviewed. Intake (volume: mL/kg/day; calorie: kcal/kg/day) and growth parameter trajectories (weight, head circumference, and length) were analyzed based on the type of prenatal opioid exposure (short-acting opioids (SAOs), long-acting opioids (LAOs), and polysubstance), pharmacologic treatment, and sex. Growth measurement patterns over time were compared between groups using longitudinal mixed-effects models. Results: One hundred nineteen infants were included in the study with median birth weight Z-score of -0.19 at birth and decreased to a median of -0.72 at discharge. Exposure to SAO was associated with an increase in Z-scores nearing discharge across all growth parameters (Z-score for weight p = 0.03). Polysubstance exposure was associated with a decrease in Z-scores for length and head circumference throughout hospitalization. Infants with adjunct clonidine treatment had an increase in Z-score for weight trends. Male infants had a decrease in Z-scores for weight (male -0.96, female -0.59, interaction p = 0.06) and length (male -1.17, female -0.57, interaction p = 0.003) at Day 28. Despite the difference in growth trajectories, intake in terms of amount (mL/kg/day) and calorie intake (kcal/kg/day) was similar based on prenatal exposure, treatment, and sex. Conclusion: Infants with NOWS requiring pharmacologic treatment have a decrease in Z-scores for weight, length, and head circumference at birth and at hospital discharge. Infants with prenatal polysubstance exposure were at particular risk for poorer inpatient growth relative to infants exposed to SAO and LAO, indicated by lower Z-scores for length and occipital frontal circumference (OFC).

Sex-Related Differences in the Severity of Neonatal Opioid Withdrawal Syndrome: A Single-Center, Retrospective Cohort Study

OBJECTIVE

 Factors associated with the development and expression of Neonatal Opioid Withdrawal Syndrome (NOWS) are poorly understood. There are conflicting data on the role of infant sex in NOWS. Some studies have suggested that infant sex predicts NOWS severity and adverse outcomes, with male infants being more vulnerable. This study aimed to analyze if infant sex is associated with the severity of NOWS among those who require pharmacologic treatment.

STUDY DESIGN

 This is a retrospective cohort study of term and late-preterm infants (≥35 weeks gestation) exposed to in utero opioids, born between September 2006 and August 2022, and required pharmacologic treatment for NOWS. Maternal and infant demographics were collected. Indicators of the severity of NOWS (duration of medical treatment (DOT), duration of hospitalization, maximum dose of opioid treatment, and use of secondary medications) were compared between male and female infants. Standard statistical tests and regression analysis were used to establish the differences in outcomes after accounting for confounders and baseline differences.

RESULTS

 Out of the 1,074 infants included in the study, 47.9% were female, and 52.1% were male. There was no significant difference in demographic and baseline clinical characteristics between groups except for anthropometry (birth weight, head circumference, and length) and Apgar score at 5 minutes. The median DOT (25 days [14, 39] vs. 23 days [13, 39], p = 0.57), length of hospital stay (31.5 days [20, 44] vs. 28 days [20, 44], p = 0.35), treatment with phenobarbital (24.7 vs. 26.3%, p = 0.56), and clonidine (3.9 vs. 3.8%, p = 0.9) were similar in both groups. The differences remained nonsignificant after adjusting for birth anthropometric measurements, gestational age, 5-minute Apgar score, small for gestational age status, and maternal exposure to benzodiazepines.

CONCLUSION

 In this cohort of neonates, sex-related differences were not identified to influence the severity of NOWS among those who required pharmacological treatment.

KEY POINTS

· Vulnerability to NOWS is multifactorial.. · The role of infant sex in the severity of NOWS is not concrete.. · We noted that sex did not impact NOWS severity in those treated..

Risk of Death at 1 Year Following Postpartum Opioid Exposure

OBJECTIVE

Opioids are commonly prescribed to women for acute pain following childbirth. Postpartum prescription opioid exposure is associated with adverse opioid-related morbidities but the association with all-cause mortality is not well studied. This study aimed to examine the association between postpartum opioid prescription fills and the 1-year risk of all-cause mortality among women with live births.

METHODS

In a retrospective cohort study of live births among women enrolled in Tennessee Medicaid (TennCare) between 2007 and 2015, we compared women who filled two or more postpartum outpatient opioid prescriptions (up to 41 days of postdelivery discharge) to women who filled one or fewer opioid prescription. Women were followed from day 42 postdelivery discharge through 365 days of follow-up or date of death. Deaths were identified using linked death certificates (2007-2016). We used Cox's proportional hazard regression and inverse probability of treatment weights to compare time to death between exposure groups while adjusting for relevant confounders. We also examined effect modification by delivery route, race, opioid use disorder, use of benzodiazepines, and mental health condition diagnosis.

RESULTS

Among 264,135 eligible births, 216,762 (82.1%) had one or fewer maternal postpartum opioid fills and 47,373 (17.9%) had two or more fills. There were 182 deaths during follow-up. The mortality rate was higher in women with two or more fills (120.5 per 100,000 person-years) than in those with one or fewer (57.7 per 100,000 person-years). The risk of maternal death remained higher in participants exposed to two or more opioid fills after accounting for relevant covariates using inverse probability of treatment weighting (adjusted hazard ratio: 1.46 [95% confidence interval: 1.01, 2.09]). Findings from stratified analyses were consistent with main findings.

CONCLUSION

Filling two or more opioid prescriptions during the postpartum period was associated with a significant increase in 1-year risk of death among new mothers.

KEY POINTS

· Opioid prescribing in the postpartum period is common.. · Prior studies show that >1 postnatal opioid fill is associated with adverse opioid-related events.. · > 1 opioid fill within 42 days of delivery was associated with an increase in 1-year risk of death..

Impact of sex, race, and social determinants of health on neonatal outcomes

Despite the global improvements in neonatal outcomes, mortality and morbidity rates among preterm infants are still unacceptably high. Therefore, it is crucial to thoroughly analyze the factors that affect these outcomes, including sex, race, and social determinants of health. By comprehending the influence of these factors, we can work towards reducing their impact and enhancing the quality of neonatal care. This review will summarize the available evidence on sex differences, racial differences, and social determinants of health related to neonates. This review will discuss sex differences in neonatal outcomes in part I and racial differences with social determinants of health in part II. Research has shown that sex differences begin to manifest in the early part of the pregnancy. Hence, we will explore this topic under two main categories: (1) Antenatal and (2) Postnatal sex differences. We will also discuss long-term outcome differences wherever the evidence is available. Multiple factors determine health outcomes during pregnancy and the newborn period. Apart from the genetic, biological, and sex-based differences that influence fetal and neonatal outcomes, racial and social factors influence the health and well-being of developing humans. Race categorizes humans based on shared physical or social qualities into groups generally considered distinct within a given society. Social determinants of health (SDOH) are the non-medical factors that influence health outcomes. These factors can include a person's living conditions, access to healthy food, education, employment status, income level, and social support. Understanding these factors is essential in developing strategies to improve overall health outcomes in communities.

Sex differences in neonatal outcomes following prenatal opioid exposure

The impact of the opioid epidemic on pregnant people and children is a growing public health crisis. Understanding how opioids affect the developing brain during pregnancy and postnatally remains a critical area of investigation. Biological sex plays a crucial role in all physiologic processes, with the potential for a significant impact on neonatal outcomes, including those infants with opioid exposure. Here, we aim to explore current literature on the effect of sex on neonatal outcomes following prenatal opioid exposure. Sex differences in adults with opioid use disorder have been well studied, including increased mortality among males and higher rates of psychiatric comorbidities and likelihood of relapse in females. However, such differences are not yet well understood in neonates. Emerging clinical data suggest sex-specific effects in infants with prenatal opioid exposure on the expression of genes related to feeding regulation and reward signaling pathways. Increased susceptibility to white matter injury has also been noted in female infants following prenatal opioid exposure. Understanding the impact of sex as a biological variable on neonatal outcomes following prenatal opioid exposure is paramount to improving the health and well-being of infants, children, and adults impacted by the opioid epidemic.

Interaction between buprenorphine and norbuprenorphine in neonatal opioid withdrawal syndrome

Buprenorphine (BUP) is the preferred treatment for opioid use disorder during pregnancy but can cause neonatal opioid withdrawal syndrome (NOWS). Norbuprenorphine (NorBUP), an active metabolite of BUP, is implicated in BUP-associated NOWS. We hypothesized that BUP, a low-efficacy agonist of mu opioid receptors, will not antagonize NorBUP, a high-efficacy agonist of mu opioid receptors, in producing NOWS. To test this hypothesis, we treated pregnant Long-Evans rats with BUP (0, 0.01, 0.1 or 1mg/kg/day) ± NorBUP (1mg/kg/day) from gestation day 9 until pup delivery, and tested pups for opioid dependence using our established NOWS model. We used LC-MS-MS to quantify brain concentrations of BUP, NorBUP, and their glucuronide conjugates. BUP had little effect on NorBUP-induced NOWS, with the exception of 1mg/kg/day BUP significantly increasing NorBUP-induced NOWS by 58% in females. BUP and NorBUP brain concentrations predicted NOWS in multiple linear regression models. Interestingly, NorBUP contributed more to NOWS in females (βNorBUP = 51.34, p = 0.0001) than in males (βNorBUP = 19.21, P = 0.093), while BUP was similar for females (βBUP = 10.62, P = 0.0017) and males (βBUP = 11.38, P = 0.009). We are the first to report that NorBUP induces NOWS in the presence of BUP and it is more influential in females than males in the contribution of NorBUP to BUP-associated NOWS. These findings suggest that females are more susceptible to NorBUP-induced NOWS, and that treatment strategies that reduce prenatal NorBUP exposure may be more effective for females than males.

The impact of gender medicine on neonatology: the disadvantage of being male: a narrative review

This narrative non-systematic review addresses the sex-specific differences observed both in prenatal period and, subsequently, in early childhood. Indeed, gender influences the type of birth and related complications. The risk of preterm birth, perinatal diseases, and differences on efficacy for pharmacological and non-pharmacological therapies, as well as prevention programs, will be evaluated. Although male newborns get more disadvantages, the physiological changes during growth and factors like social, demographic, and behavioural reverse this prevalence for some diseases. Therefore, given the primary role of genetics in gender differences, further studies specifically targeted neonatal sex-differences will be needed to streamline medical care and improve prevention programs.

Potential problems and solutions of opioid-based treatment in neonatal opioid withdrawal syndrome (NOWS): a scoping review protocol

INTRODUCTION

Rates of neonatal opioid withdrawal syndrome (NOWS) have paralleled the rise of opioid use during pregnancy. While short-term phenotypic symptoms of NOWS are well defined, molecular implications and long-term effects are not well understood. Preferred and first-line of treatment for NOWS includes non-pharmacological interventions; however, more than half of the NOWS neonates will need pharmacologics, with opioids as the primary pharmacological treatment. While effective at reducing symptoms, treating NOWS with opioids is paradoxical given that molecular and long-term developmental consequences with such exposure are unknown. There is a pressing need for a synthesis of current and potential/ novel treatment options for NOWS.

METHODS AND ANALYSIS

Following a published framework, a scoping review will be conducted to evaluate NOWS treatment, including established treatment methods and novel methods that may warrant future research and consideration. Using broad search terms, as well as Medical Subject Headings terms, a comprehensive search of PubMed, Cochrane Library, Google Scholar, CINAHL, Web of Science and Scopus, as well as references of selected literature, will take place, followed by a screening procedure to identify included and excluded articles. Included studies must address NOWS treatment, or opioid withdrawal treatment of any age group, that may or may not have been tested in preclinical or clinical models. Results will summarise the current pharmacological and non-pharmacological treatment methods for NOWS, as well as potential novel treatments with a specific interest in non-opioid pharmacological interventions.

ETHICS AND DISSEMINATION

This scoping review aims to broadly search preclinical and clinical literature as it relates to treatment of NOWS, including potential novel treatments with a specific interest in non-opioid pharmacological interventions. Given that this study does not directly involve human subjects or animal subjects research, Institutional Review Board (IRB) or Institutional Animal Care and Use Committee (IACUC) approval is not required. Results of this scoping review will be disseminated at conferences and submitted for publication in a peer-reviewed journal.

A review of the genomics of neonatal abstinence syndrome

Neonatal abstinence syndrome (NAS) is a constellation of signs of withdrawal occurring after birth following in utero exposure to licit or illicit opioids. Despite significant research and public health efforts, NAS remains challenging to diagnose, predict, and manage due to highly variable expression. Biomarker discovery in the field of NAS is crucial for stratifying risk, allocating resources, monitoring longitudinal outcomes, and identifying novel therapeutics. There is considerable interest in identifying important genetic and epigenetic markers of NAS severity and outcome that can guide medical decision making, research efforts, and public policy. A number of recent studies have suggested that genetic and epigenetic changes are associated with NAS severity, including evidence of neurodevelopmental instability. This review will provide an overview of the role of genetics and epigenetics in short and longer-term NAS outcomes. We will also describe novel research efforts using polygenic risk scores for NAS risk stratification and salivary gene expression to understand neurobehavioral modulation. Finally, emerging research focused on neuroinflammation from prenatal opioid exposure may elucidate novel mechanisms that could lead to development of future novel therapeutics.

Sex-specific inflammatory and white matter effects of prenatal opioid exposure: a pilot study

BACKGROUND

Preclinical data demonstrate that opioids modulate brain reward signaling through an inflammatory cascade, but this relationship has yet to be studied in opioid-exposed neonates.

METHODS

Saliva samples of 54 opioid-exposed and sex- and age-matched non-exposed neonates underwent transcriptomic analysis of inflammatory and reward genes. A subset of 22 neonates underwent brain magnetic resonance imaging (MRI) to evaluate white matter injury commonly associated with inflammatory response. Gene expression and brain MRI were compared between opioid- and non-exposed neonates and further stratified by sex and pharmacotherapy need.

RESULTS

Opioid-exposed females regardless of pharmacotherapy need had higher expression of inflammatory genes than their male counterparts, with notable differences in the expression of CCL2 and CXCL1 in females requiring pharmacotherapy (p = 0.01 and 0.06, respectively). Opioid-exposed males requiring pharmacotherapy had higher expression of DRD2 than exposed females (p = 0.07), validating our prior research. Higher expression of IL1β, IL6, TNFα, and IL10 was seen in opioid-exposed neonates with T1 white matter hyperintensity (WMH) compared to exposed neonates without WMH (p < 0.05).

CONCLUSION

Prenatal opioid exposure may promote inflammation resulting in changes in reward signaling and white matter injury in the developing brain, with unique sex-specific effects. The actions of opioids through non-neuronal pathways need further investigation.

IMPACT

Opioid-exposed neonates are at risk for punctate T1 white matter hyperintensity (WMH). Females carry a greater propensity for WMH. Salivary transcriptomic data showed significantly higher expression of inflammatory genes in opioid-exposed neonates with WMH than those without WMH, irrespective of pharmacotherapy need. Adding to prior studies, our findings suggest that prenatal opioid exposure may modulate white matter injury and reward signaling through a pro-inflammatory process that is sex specific. This novel study highlights the short-term molecular and structural effects of prenatal opioids and the need to elucidate the long-term impact of prenatal opioid exposure.

Effects of prenatal opioid exposure on synaptic adaptations and behaviors across development

In this review, we focus on prenatal opioid exposure (POE) given the significant concern for the mental health outcomes of children with parents affected by opioid use disorder (OUD) in the view of the current opioid crisis. We highlight some of the less explored interactions between developmental age and sex on synaptic plasticity and associated behavioral outcomes in preclinical POE research. We begin with an overview of the rich literature on hippocampal related behaviors and plasticity across POE exposure paradigms. We then discuss recent work on reward circuit dysregulation following POE. Additional risk factors such as early life stress (ELS) could further influence synaptic and behavioral outcomes of POE. Therefore, we include an overview on the use of preclinical ELS models where ELS exposure during key critical developmental periods confers considerable vulnerability to addiction and stress psychopathology. Here, we hope to highlight the similarity between POE and ELS on development and maintenance of opioid-induced plasticity and altered opioid-related behaviors where similar enduring plasticity in reward circuits may occur. We conclude the review with some of the limitations that should be considered in future investigations. This article is part of the Special Issue on 'Opioid-induced addiction'.

Prediction model for nonopiate-induced neonatal abstinence syndrome

BACKGROUND

Neonatal abstinence syndrome (NAS) induced by opiate use is common worldwide. Psychiatric drugs are a more common cause of NAS in Japan but infants of mothers taking psychiatric medications do not always develop NAS. The purpose of this study was to develop a practical model for predicting the onset of nonopiate-induced NAS, using variables available at birth.

METHODS

In this diagnostic study, prediction models were developed using multivariable logistic regression with retrospective data collected at our hospital between 2010 and 2019. The NAS diagnosis was based on the Isobe score, and maternal medications were converted to dose equivalents.

RESULTS

A total of 164 maternal and infant dyads met the inclusion criteria; 91 were included in the analysis, of whom 29 infants (32%) were diagnosed with NAS. Final models were created with and without the drug indices. The model without the drug indices consisted of neonatal head circumference in z-scores and Apgar scores at 5 min < 9, and the model with the drug indices included these, as well as antipsychotics and hypnotics indices. The C-statistics were 0.747 (95% CI: 0.638-0.856), and 0.795 (95% CI: 0.683-0.907), respectively, indicating that the models possessed good predictive accuracy for NAS onset.

CONCLUSIONS

This study developed models that predicted nonopiate-induced NAS accurately. They may be further improved through the use of drug indices.

Perinatal Morphine Exposure Leads to Sex-Dependent Executive Function Deficits and Microglial Changes in Mice

Children exposed prenatally to opioids are at an increased risk for behavioral problems and executive function deficits. The prefrontal cortex (PFC) and amygdala (AMG) regulate executive function and social behavior and are sensitive to opioids prenatally. Opioids can bind to toll-like receptor 4 (TLR4) to activate microglia, which may be developmentally important for synaptic pruning. Therefore, we tested the effects of perinatal morphine exposure on executive function and social behavior in male and female mouse offspring, along with microglial-related and synaptic-related outcomes. Dams were injected once daily subcutaneously with saline (n = 8) or morphine (MO; 10 mg/kg; n = 12) throughout pregestation, gestation, and lactation until offspring were weaned on postnatal day 21 (P21). Male MO offspring had impairments in attention and accuracy in the five-choice serial reaction time task, while female MO offspring were less affected. Targeted gene expression analysis at P21 in the PFC identified alterations in microglial-related and TLR4-related genes, while immunohistochemical analysis in adult brains indicated decreased microglial Iba1 and phagocytic CD68 proteins in the PFC and AMG in males, but females had an increase. Further, both male and female MO offspring had increased social preference. Overall, these data demonstrate male vulnerability to executive function deficits in response to perinatal opioid exposure and evidence for disruptions in neuron-microglial signaling.

A population-based descriptive study of neonatal abstinence syndrome using hospital discharge and birth certificate data

BACKGROUND

Neonatal abstinence syndrome (NAS), largely a consequence of prenatal opioid exposure, results in substantial morbidity. Population-based studies of NAS going beyond Medicaid populations and hospital discharge data (HDD) alone are limited. Using statewide Tennessee (TN) HDD and birth certificate (BC) data, we examined trends and evaluated maternal and infant factors associated with NAS.

METHODS

We conducted a population-based descriptive study during 2013-2017 in TN. NAS infants were identified with International Classification of Diseases (ICD)-9-Clinical Modification (CM) and ICD-10-CM codes in HDD and linked to BC data using iterative deterministic matching algorithms. Descriptive analyses were conducted for infant and maternal factors (exposures) by NAS (outcome). Multivariable logistic regression models were used to estimate adjusted ORs and 95% CIs.

RESULTS

NAS incidence increased from 13.4 to 15.4 per 1,000 live births between 2013-2017 (15% increase; ptrend<0.001), but remained stable in 2017. In adjusted models, maternal factors associated with reduced odds of NAS included breastfeeding (OR:0.55, 95%CI:0.52-0.59) and prenatal care (OR:0.36, 95%CI:0.32-0.41). Smoking, preterm birth and lower birthweight were associated with increased odds of NAS.

CONCLUSIONS

This study highlights the value of utilizing surveillance data to monitor trends and correlates of NAS to inform prevention efforts and targeting of public health resources.

Elucidating the Relationship Between Maternal Diabetes and Neonatal Abstinence Syndrome: A 2017-2018 Project WATCH Study in Rural Appalachia

BACKGROUND

Previous research indicated that diabetes during pregnancy results in a more permeable placenta. Based on this data, we hypothesized that women with maternal diabetes were more likely to have infants who developed neonatal abstinence syndrome (NAS).

PURPOSE

The purpose of the study was to examine the association between maternal diabetes and NAS in a cohort of women reporting substance use during pregnancy.

METHODS

This study used data from a population-based cohort of all newborns born in 2017 and 2018 (N = 36,974) in the state of West Virginia and restricted the analysis to those infants with intrauterine substance exposure (14%, n = 5188). Multiple logistic regression was performed to analyze the adjusted relationship between maternal diabetes and NAS while controlling for maternal and infant covariates.

RESULTS

Just over 28% of women with diabetes had an infant who developed NAS, whereas 34.8% of women without diabetes had an infant who developed NAS. The adjusted odds ratio of infants developing NAS born to women with diabetes was 0.70 (95% confidence interval: 0.51, 0.94) compared with those born to mothers without diabetes after controlling for covariates. Contrary to our hypothesis, the study suggests that maternal diabetes during pregnancy is associated with a decreased risk of an infant developing NAS.

IMPLICATIONS FOR PRACTICE

Future research generating from this hypothesis may lead to potential implications for practice for infants born to mothers with substance use during pregnancy and diabetes.

IMPLICATIONS FOR RESEARCH

More research should be conducted to investigate the relationship between glucose metabolism and NAS.

Neonatal Opioid Withdrawal Syndrome: A Comparison of As-Needed Pharmacotherapy

BACKGROUND AND OBJECTIVE

Methadone and morphine are commonly administered medications for neonatal opioid withdrawal syndrome (NOWS). Infants are increasingly treated with as-needed or "pro re nata" (PRN) medication. The optimal pharmacologic agent for PRN treatment of NOWS has not been examined. This study's objective is to compare NOWS hospital outcomes between infants treated with PRN methadone versus morphine.

METHODS

We performed a retrospective cohort study of infants pharmacologically treated for NOWS across 4 Massachusetts hospitals between January 2018 and February 2021. Infants born ≥36 weeks gestation with prenatal opioid exposure treated with PRN methadone or morphine were included. Mixed effects logistic and linear regression models were employed to evaluate differences in transition rates to scheduled dosing, length of stay, and number of PRN doses administered depending on PRN treatment agent.

RESULTS

There were 86 infants in the methadone group and 52 in the morphine group. There were no significant differences in NOWS hospital outcomes between groups in adjusted models: transition to scheduled dosing (methadone 31.6% vs morphine 28.6%, adjusted odds ratio 1.21, 95% confidence interval [CI] 0.87-1.19), mean length of stay (methadone 15.5 vs morphine 14.3 days, adjusted risk ratio 1.06, 95% CI 0.80-1.41), and the mean number of PRN doses (methadone 2.3 vs morphine 3.4, adjusted risk ratio 0.65, 95% CI 0.41-1.02). There was an association with nonpharmacologic care practices and improved NOWS hospital outcomes.

CONCLUSIONS

There were no significant differences in NOWS hospitalization outcomes based on pharmacologic agent type; nonpharmacologic care practices were most strongly associated with improved NOWS hospitalization outcomes.

Prenatal opioid-exposed infant extracellular miRNA signature obtained at birth predicts severity of neonatal opioid withdrawal syndrome

Prenatal opioid exposure (POE) is commonly associated with neonatal opioid withdrawal syndrome (NOWS), which is characterized by a broad variability in symptoms and severity. Currently there are no diagnostic tools to reliably predict which infants will develop severe NOWS, while risk stratification would allow for proactive decisions about appropriate clinical monitoring and interventions. The aim of this prospective cohort study was to assess if extracellular microRNAs (miRNAs) in umbilical cord plasma of infants with POE could predict NOWS severity. Participants (n = 58) consisted of pregnant women receiving medications for opioid use disorder and their infants. NOWS severity was operationalized as the need for pharmacologic treatment and prolonged hospitalization (≥ 14 days). Cord blood miRNAs were assessed using semi-quantitative qRT-PCR arrays. Receiver operating characteristic curves and area under the curve (AUC) were estimated. The expression of three miRNAs (miR-128-3p, miR-30c-5p, miR-421) predicted need for pharmacologic treatment (AUC: 0.85) and prolonged hospitalization (AUC: 0.90). Predictive validity improved after two miRNAs (let-7d-5p, miR-584-5p) were added to the need for pharmacologic treatment model (AUC: 0.94) and another two miRNAs (let-7b-5p, miR-10-5p) to the prolonged hospitalization model (AUC: 0.99). Infant cord blood extracellular miRNAs can proactively identify opioid-exposed neonates at high-risk for developing severe NOWS.

Severity of neonatal opioid withdrawal syndrome with prenatal exposure to serotonin reuptake inhibitors

OBJECTIVE

To evaluate the severity of neonatal opioid withdrawal syndrome (NOWS) in infants prenatally exposed to medications for opioid use disorder (MOUD) and serotonin reuptake inhibitors (SRI).

METHODS

A prospective cohort included 148 maternal-infant pairs categorized into MOUD (n = 127) and MOUD + SRI (n = 27) groups. NOWS severity was operationalized as the infant's need for pharmacologic treatment with opioids, duration of hospitalization, and duration of treatment. The association between prenatal SRI exposure and the need for pharmacologic treatment (logistic regression), time-to-discharge, and time-to-treatment discontinuation (Cox proportional hazards modeling) was examined after adjusting for the type of maternal MOUD, use of hydroxyzine, other opioids, benzodiazepines/sedatives, alcohol, tobacco, marijuana, gestational age, and breastfeeding.

RESULTS

Infants in the MOUD + SRI group were more likely to receive pharmacologic treatment for NOWS (OR = 3.58; 95% CI: 1.31; 9.76) and had a longer hospitalization (median: 11 vs. 6 days; HR = 0.54; 95% CI: 0.33; 0.89) compared to the MOUD group. With respect to time-to-treatment discontinuation, no association was observed in infants who received treatment (HR = 0.59; 95% CI: 0.26, 1.32); however, significant differences were observed in the entire sample (HR = 0.55; 95% CI: 0.34, 0.89).

CONCLUSIONS

Use of SRIs among pregnant women on MOUD might be associated with more severe NOWS.

IMPACT

A potential drug-drug interaction between maternal SRIs and opioid medications that inhibit the reuptake of serotonin has been hypothesized but not carefully evaluated in clinical studies. Results of this prospective cohort indicate that the use of SRIs among pregnant women on MOUD is associated with more severe neonatal opioid withdrawal syndrome. This is the first prospective study which carefully examined effect modification between the type of maternal MOUD and SRI use on neonatal outcomes. This report lays the foundation for treatment optimization in pregnant women with co-occurring mental health and substance use disorders.

Does Maternal Incarceration Impact Infants with Neonatal Abstinence Syndrome?

OBJECTIVES

Opioid exposed infants born to incarcerated women represent a vulnerable and understudied subset of infants with neonatal abstinence syndrome (NAS). The impact of maternal incarceration on length of stay (LOS) for infants with NAS is unknown. We hypothesized that infants with NAS born to incarcerated women have longer hospitalizations compared to infants with NAS born to non-incarcerated women.

METHODS

This is a retrospective cohort study of infants with NAS born between 2011 and 2018 at the primary delivery site for Connecticut's only women's prison. Opioid exposed infants were assessed by Finnegan Scores for withdrawal and received morphine as a first line agent and phenobarbital as a second line agent. LOS was compared using Poisson regression.

RESULTS

Of 206 infants identified, 166 were included in the analysis, with 28 born to incarcerated women and 138 to non-incarcerated women. Incarcerated women were more likely to report prenatal alcohol use, 14.3% vs 2.2% p = 0.016 and benzodiazepine use 21.4% vs 7.3% p = 0.032. Infants of incarcerated women were less likely to be fed breast milk at discharge, 3.6% vs 37% p < 0.001. Adjusted mean LOS was longer among infants born to incarcerated women, 18.5 vs 16.6 days (p = 0.009).

CONCLUSIONS FOR PRACTICE

Infants with NAS born to incarcerated women in Connecticut had longer LOS, lower rates of being fed breast milk, and different prenatal substance exposures than infants with NAS born to non-incarcerated women. Supporting the maternal-infant dyad until infant discharge may mitigate the potential negative impact of maternal incarceration on the care of infants with NAS.

Association between punitive policies and neonatal abstinence syndrome among Medicaid-insured infants in complex policy environments

AIMS

To estimate the association between punitive policies for women with substance use during pregnancy and odds of neonatal abstinence syndrome (NAS) diagnosis among Medicaid-insured infants, and to estimate this association controlling for the presence of four other policies related to substance use in pregnancy.

DESIGN, SETTING AND PARTICIPANTS

Analysis of live births in Medicaid claims data from 39 US states in varying years between 2006 and 2014 using weighted generalized linear models with clustered standard errors and state and year fixed-effects.

MEASUREMENTS

NAS rates in states without punitive policies were compared with rates in states with policies before and after policy enactment using logistic regression models adjusted for individual and county-level factors and including state and year fixed-effects. We estimated odds of NAS controlling for the presence of a potentially treatment-deterring policy requiring reporting of suspected prenatal substance use, and three treatment-supportive policies that create targeted programs for pregnant and postpartum women, prioritize pregnant women's access to substance use disorder treatment programs and prohibit discrimination towards pregnant women in treatment programs.

FINDINGS

Among 9 714 798 weighted live births (1 896 082 unweighted), 49 670 (0.51%) had an NAS diagnosis. The findings were inconclusive as to whether or not punitive policies were associated with odds of NAS either in the short or long term. Odds of NAS among infants born in states with reporting policies were lower than those born in states without such policies [adjusted odds ratio (aOR) = 0.77, 95% confidence interval (CI) = 0.61-0.98].

CONCLUSIONS

In the United States, punitive policies for women with substance use during pregnancy do not appear to be associated with lower odds of neonatal abstinence syndrome (NAS). Reporting policies, which are heterogenous in their components and implementation, appear to be associated with lower odds of NAS when controlling for other relevant policies.

Sex Differences in Behavioral and Brainstem Transcriptomic Neuroadaptations following Neonatal Opioid Exposure in Outbred Mice

The opioid epidemic led to an increase in the number of neonatal opioid withdrawal syndrome (NOWS) cases in infants born to opioid-dependent mothers. Hallmark features of NOWS include weight loss, severe irritability, respiratory problems, and sleep fragmentation. Mouse models provide an opportunity to identify brain mechanisms that contribute to NOWS. Neonatal outbred Swiss Webster Cartworth Farms White (CFW) mice were administered morphine (15 mg/kg, s.c.) twice daily from postnatal day 1 (P1) to P14, an approximation of the third trimester of human gestation. Female and male mice underwent behavioral testing on P7 and P14 to determine the impact of opioid exposure on anxiety and pain sensitivity. Ultrasonic vocalizations (USVs) and daily body weights were also recorded. Brainstems containing pons and medulla were collected during morphine withdrawal on P14 for RNA sequencing. Morphine induced weight loss from P2 to P14, which persisted during adolescence (P21) and adulthood (P50). USVs markedly increased at P7 in females, emerging earlier than males. On P7 and P14, both morphine-exposed female and male mice displayed hyperalgesia on the hot plate and tail-flick assays, with females showing greater hyperalgesia than males. Morphine-exposed mice exhibited increased anxiety-like behavior in the open-field arena on P21. Transcriptome analysis of the brainstem, an area implicated in opioid withdrawal and NOWS, identified pathways enriched for noradrenergic signaling in females and males. We also found sex-specific pathways related to mitochondrial function and neurodevelopment in females and circadian entrainment in males. Sex-specific transcriptomic neuroadaptations implicate unique neurobiological mechanisms underlying NOWS-like behaviors.

Prenatal exposure to opioids: Associations between the caregiving environment and externalizing behaviors

Maternal opioid use during pregnancy is a rapidly growing public health crisis and is associated with a range of adverse developmental outcomes including externalizing behaviors among exposed children. Recent work has highlighted the role of indirect pathways from prenatal opioid exposure to behavioral outcomes through aspects of the caregiving environment, including parenting. This review highlights maternal sensitivity and related aspects of the caregiving environment that may impact the development of externalizing behaviors among children with a history of prenatal exposure to opioids. We conclude by providing suggestions for future directions in research examining development among children with prenatal opioid exposure.

Predictors of pharmacologic therapy for neonatal opioid withdrawal syndrome: a retrospective analysis of a statewide database

OBJECTIVE

Identify factors associated with the need for pharmacologic therapy (PT) among opioid exposed newborn (OENs).

STUDY DESIGN

Retrospective analysis of a statewide database of OENs from 2017 through 2019. Multivariable mixed-effects logistic regression modeled the association of maternal characteristics, infant characteristics, and family engagement practices on the receipt of PT.

RESULTS

Of 2098 OENs, 44.8% required PT for NOWS. Higher odds of PT were associated with in-utero exposure to medication treatment for opioid use disorder (MOUD) and non-prescribed opioids in addition to MOUD; nicotine, benzodiazepines, SSRIs; male; out-born infants and mother's ineligibility to provide breast-milk. Lower odds were associated with increasing birth year, skin-to-skin (STS) care, and rooming-in.

CONCLUSION

Male, out-born infants exposed to MOUD with additional non-prescribed opioids, nicotine, benzodiazepines and SSSRIs with mothers ineligible to provide breast-milk were more likely to require PT, while modifiable care practices including STS care, and rooming-in decreased the likelihood of PT.

Project Console: a quality improvement initiative for neonatal abstinence syndrome in a children's hospital level IV neonatal intensive care unit

Objective

To improve care for infants with neonatal abstinence syndrome.

Design

Infants with a gestational age of ≥35 weeks with prenatal opioid exposure were eligible for our quality improvement initiative. Interventions in our Plan–Do–Study–Act cycles included physician consensus, re-emphasis on non-pharmacological treatment, the Eat Sleep Console method to measure functional impairment, morphine as needed, clonidine and alternative soothing methods for parental unavailability (volunteer cuddlers and automated sleeper beds). Pre-intervention and post-intervention outcomes were compared.

Results

Length of stay decreased from 31.8 to 10.5 days (p<0.0001) without an increase in readmissions. Composite pharmacotherapy exposure days decreased from 28.7 to 5.5 (p<0.0001). This included reductions in both morphine exposure days (p<0.0001) and clonidine exposure days (p=0.01). Fewer infants required pharmacotherapy (p=0.02).

Conclusions

Our study demonstrates how a comprehensive initiative can improve care for infants with neonatal abstinence syndrome in an open-bay or a high-acuity neonatal intensive care unit when rooming-in is not available or other comorbidities are present.

Maternal and iatrogenic neonatal opioid withdrawal syndrome: Differences and similarities in recognition, management, and consequences

Opioids are potent analgesics used to manage pain in both young and old, but the increased use in the pregnant population has significant individual and societal implications. Infants dependent on opioids, either through maternal or iatrogenic exposure, undergo neonatal opioid withdrawal syndrome (NOWS), where they may experience withdrawal symptoms ranging from mild to severe. We present a detailed and original review of NOWS caused by maternal opioid exposure (mNOWS) and iatrogenic opioid intake (iNOWS). While these two entities have been assessed entirely separately, recognition and treatment of the clinical manifestations of NOWS overlap. Neonatal risk factors such as age, genetic predisposition, drug type, and clinical factors like type of opioid, cumulative dose of opioid exposure, and disease status affect the incidence of both mNOWS and iNOWS, as well as their severity. Recognition of withdrawal is dependent on clinical assessment of symptoms, and the use of clinical assessment tools designed to determine the need for pharmacotherapy. Treatment of NOWS relies on a combination of non-pharmacological therapies and pharmacological options. Long-term consequences of opioids and NOWS continue to generate controversy, with some evidence of anatomic brain changes, but conflicting animal and human clinical evidence of significant cognitive or behavioral impacts on school-age children. We highlight the current knowledge on clinically relevant recognition, treatment, and consequences of NOWS, and identify new advances in clinical management of the neonate. This review brings a unique clinical perspective and critically analyzes gaps between the clinical problem and our preclinical understanding of NOWS.

Phenobarbital and Clonidine as Secondary Medications for Neonatal Opioid Withdrawal Syndrome

BACKGROUND AND OBJECTIVES

Despite the neonatal opioid withdrawal syndrome (NOWS) epidemic in the United States, evidence is limited for pharmacologic management when first-line opioid medications fail to control symptoms. The objective with this study was to evaluate outcomes of infants receiving secondary therapy with phenobarbital compared with clonidine, in combination with morphine, for the treatment of NOWS.

METHODS

We performed a retrospective cohort study of infants with NOWS from 30 hospitals. The primary outcome measures were the length of hospital stay, duration of opioid treatment, and peak morphine dose. Outcomes were compared by group by using analysis of variance and multivariable linear regression controlling for relevant confounders.

RESULTS

Of 563 infants with NOWS treated with morphine, 32% (n = 180) also received a secondary medication. Seventy-two received phenobarbital and 108 received clonidine. After adjustment for covariates, length of hospital stay was 10 days shorter, and, in some models, duration of morphine treatment was 7.5 days shorter in infants receiving phenobarbital compared with those receiving clonidine, with no difference in peak morphine dose. Infants were more likely to be discharged from the hospital on phenobarbital than clonidine (78% vs 29%, P < .0001).

CONCLUSIONS

Among infants with NOWS receiving morphine and secondary therapy, those treated with phenobarbital had shorter length of hospital stay and shorter morphine treatment duration than clonidine-treated infants but were discharged from the hospital more often on secondary medication. Further investigation is warranted to determine if the benefits of shorter hospital stay and shorter duration of morphine therapy justify the possible neurodevelopmental consequences of phenobarbital use in infants with NOWS.

Ontogenetic Oxycodone Exposure Affects Early Life Communicative Behaviors, Sensorimotor Reflexes, and Weight Trajectory in Mice

Nationwide, opioid misuse among pregnant women has risen four-fold from 1999 to 2014, with commensurate increase in neonates hospitalized for neonatal abstinence syndrome (NAS). NAS occurs when a fetus exposed to opioids in utero goes into rapid withdrawal after birth. NAS treatment via continued post-natal opioid exposure has been suggested to worsen neurodevelopmental outcomes. We developed a novel model to characterize the impact of in utero and prolonged post-natal oxycodone (Oxy) exposure on early behavior and development. Via subcutaneous pump implanted before breeding, C57BL/6J dams were infused with Oxy at 10 mg/kg/day from conception through pup-weaning. At birth, in utero oxy-exposed pups were either cross-fostered (paired with non-Oxy exposed dams) to model opioid abstinence (in utero Oxy) or reared by their biological dams still receiving Oxy to model continued post-natal opioid exposure (prolonged Oxy). Offspring from vehicle-exposed dams served as cross-fostered (in utero Veh) or biologically reared (prolonged Veh) controls. In utero Oxy exposure resulted in sex-dependent weight reductions and altered spectrotemporal features of isolation-induced ultrasonic vocalization (USV). Meanwhile, prolonged Oxy pups exhibited reduced weight and sex-differential delays in righting reflex. Specifically, prolonged Oxy female offspring exhibited increased latency to righting. Prolonged Oxy pups also showed decreases in number of USV calls and changes to spectrotemporal USV features. Overall, ontogenetic Oxy exposure was associated with impaired attainment of gross and sensorimotor milestones, as well as alterations in communication and affective behaviors, indicating a need for therapeutic interventions. The model developed here will enable studies of withdrawal physiology and opioid-mediated mechanisms underlying these neurodevelopmental deficits.

Development and Validation of a Model to Predict Neonatal Abstinence Syndrome

OBJECTIVES

To develop and validate clinical risk prediction tools for neonatal abstinence syndrome (NAS).

STUDY DESIGN

We developed prediction models for NAS based on a set of 30 demographic and antenatal exposure covariates collected during pregnancy. Data (outpatient prescription, vital, and administrative records), were obtained from enrollees in the Tennessee Medicaid Program from 2009 to 2014. Models were created using logistic regression and backward selection based on improvement in the Akaike information criterion, and internally validated using bootstrap cross-validation.

RESULTS

A total of 218 020 maternal and infant dyads met inclusion criteria, of whom 3208 infants were diagnosed with NAS. The general population model included age, hepatitis C virus infection, days of opioid used by type, number of cigarettes used daily, and the following medications used in the last 30 day of pregnancy: bupropion, antinausea medicines, benzodiazepines, antipsychotics, and gabapentin. Infant characteristics included birthweight, small for gestational age, and infant sex. A high-risk model used a smaller number of predictive variables. Both models discriminated well with an area under the curve of 0.89 and were well-calibrated for low-risk infants.

CONCLUSIONS

We developed 2 predictive models for NAS based on demographics and antenatal exposure during the last 30 days of pregnancy that were able to risk stratify infants at risk of developing the syndrome.

Aberrant Feeding and Growth in Neonates With Prenatal Opioid Exposure: Evidence of Neuromodulation and Behavioral Changes

Opioid use disorder (OUD) among pregnant women over the last decade has led to more than a fivefold increase in the number of neonates born with withdrawal signs known as Neonatal Abstinence Syndrome (NAS) or Neonatal Opioid Withdrawal Syndrome (NOWS). The impact of prenatal opioid exposure on these neonates remains a public health and research priority due to both its short and long-term effects on offspring. Among the adverse long-term effects associated with OUD is a metabolic syndrome with accompanying cardiovascular comorbidities. The susceptibility to metabolic diseases may begin as early as conception. Neonates born in a setting of prenatal opioid exposure are known to have aberrant early growth, e.g., lower birth weight and smaller head size, and dysregulated feeding behavior that ranges from feeding difficulty to hyperphagia which may predispose these neonates to metabolic syndrome in adulthood. However, studies on this topic are lacking. In this article, we describe the reported association between OUD and metabolic syndrome in adults, animal data linking opioid receptors with the development of diet-induced obesity, the inflammatory modulation of opioids and finally, neonatal salivary transcriptomic data from our laboratory that highlighted the sex-specific impact of opioids on the hypothalamic and reward receptors that regulate feeding behavior in opioid-exposed neonates. There is a great need for future research linking opioids with epigenetic and gene expression changes, as well as neuromodulatory effects in the developing brain, that may underlie the dysregulated feeding, growth, and long-term metabolic and cardiovascular risks for these neonates.

Racial and Ethnic Disparities in Maternal and Infant Outcomes Among Opioid-Exposed Mother-Infant Dyads in Massachusetts (2017-2019)

Objectives. To examine the extent to which differences in medication for opioid use disorder (MOUD) in pregnancy and infant neonatal opioid withdrawal syndrome (NOWS) outcomes are associated with maternal race/ethnicity.Methods. We performed a secondary analysis of a statewide quality improvement database of opioid-exposed deliveries from January 2017 to April 2019 from 24 hospitals in Massachusetts. We used multivariable mixed-effects logistic regression to model the association between maternal race/ethnicity (non-Hispanic White, non-Hispanic Black, or Hispanic) and prenatal receipt of MOUD, NOWS severity, early intervention referral, and biological parental custody at discharge.Results. Among 1710 deliveries to women with opioid use disorder, 89.3% (n = 1527) were non-Hispanic White. In adjusted models, non-Hispanic Black women (AOR = 0.34; 95% confidence interval [CI] = 0.18, 0.66) and Hispanic women (AOR = 0.43; 95% CI = 0.27, 0.68) were less likely to receive MOUD during pregnancy compared with non-Hispanic White women. We found no statistically significant associations between maternal race/ethnicity and infant outcomes.Conclusions. We identified significant racial/ethnic differences in MOUD prenatal receipt that persisted in adjusted models. Research should focus on the perspectives and treatment experiences of non-Hispanic Black and Hispanic women to ensure equitable care for all mother-infant dyads.

Neonatal Abstinence Syndrome Severity Index Predicts 18-Month Neurodevelopmental Outcome in Neonates Randomized to Morphine or Methadone

OBJECTIVE

To develop an index to determine which opioid-exposed neonates have the most severe neonatal abstinence syndrome (NAS).

STUDY DESIGN

Full-term neonates with NAS (n = 116) from mothers maintained on methadone or buprenorphine were enrolled from 8 sites into a randomized clinical trial of morphine vs methadone. Ninety-nine (85%) were evaluated at hospital discharge using the NICU Network Neurobehavioral Scale (NNNS). At 18 months, 83 of 99 (83.8%) were evaluated with the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III), and 77 of 99 (77.7%) were evaluated with the Child Behavior Checklist (CBCL).

RESULTS

Cluster analysis was used to define high (n = 21) and low (n = 77) NAS severity. Compared with infants in the low NAS severity cluster, infants in the high NAS severity cluster had a longer length of stay (P < .001), longer length of stay due to NAS (P < .001), longer duration of treatment due to NAS (P < .001), and higher total dose of the study drug (P < .001) and were more likely to have received phenobarbital (P < .001), to have been treated with morphine (P = .020), and to have an atypical NNNS profile (P = .005). The 2 groups did not differ in terms of maximum Finnegan score. At 18 months, in unadjusted analyses, compared with the high-severity cluster, the low-severity cluster had higher scores on the Bayley-III Cognitive (P = .013), Language (P < .001), and Motor (P = .041) composites and less total behavior problems on the CBCL (P = .028). In adjusted analyses, the difference in the Bayley-III Language composite remained (P = .013).

CONCLUSIONS

Presumptive measures of NAS severity can be aggregated to develop an index that predicts developmental outcomes at age 18 months.

Clinical and basic research investigations into the long-term effects of prenatal opioid exposure on brain development

Coincident with the opioid epidemic in the United States has been a dramatic increase in the number of children born with neonatal abstinence syndrome (NAS), a form of withdrawal resulting from opioid exposure during pregnancy. Many research efforts on NAS have focused on short-term care, including acute symptom treatment and weaning of the infants off their drug dependency prior to authorizing their release. However, investigations into the long-term effects of prenatal opioid exposure (POE) on brain development, from the cellular to the behavioral level, have not been as frequent. Given the importance of the perinatal period for human brain development, opioid-induced disturbances in the formation and function of nascent synaptic networks and glia have the potential to impact brain connectivity and cognition long after the drug supply is cutoff shortly after birth. In this review, we will summarize the current state of NAS research, bringing together findings from human studies and preclinical animal models to highlight what is known about how POE can induce significant, prolonged deficits in brain structure and function. With rates of NAS continuing to rise, particularly in regions that already face substantial socioeconomic challenges, we speculate as to the most promising avenues for future research to alleviate this growing multigenerational threat.

Association of a Simplified Finnegan Neonatal Abstinence Scoring Tool With the Need for Pharmacologic Treatment for Neonatal Abstinence Syndrome

IMPORTANCE

Observer-rated scales, such as the Finnegan Neonatal Abstinence Scoring Tool (FNAST), are used to quantify the severity of neonatal abstinence syndrome (NAS) and guide pharmacologic therapy. The FNAST, a comprehensive 21-item assessment tool, was developed for research and subsequently integrated into clinical practice; a simpler tool, designed to account for clinically meaningful outcomes, is urgently needed to standardize assessment.

OBJECTIVES

To identify FNAST items independently associated with the decision to use pharmacologic therapy and to simplify the FNAST while minimizing loss of information for the treatment decision.

DESIGN, SETTING, AND PARTICIPANTS

This multisite cohort study included 424 neonates with opioid exposure who had a gestational age of at least 36 weeks with follow-up from birth to hospital discharge in the derivation cohort and 109 neonates with opioid exposure from the Maternal Opioid Treatment: Human Experimental Research Study in the validation cohort. Neonates in the derivation cohort were included in a medical record review at the Universities of Louisville and Kentucky or in a randomized clinical trial and observational study conducted at Tufts University (2014-2018); the Maternal Opioid Treatment: Human Experimental Research was conducted from 2005 to 2008. Data analysis was conducted from May 2017 to August 2019.

EXPOSURES

Prenatal opioid exposure.

MAIN OUTCOMES AND MEASURES

All FNAST items were dichotomized as present or not present, and logistic regression was used to identify binary items independently associated with pharmacologic treatment. The final model was validated with an independent cohort of neonates with opioid exposure.

RESULTS

Among 424 neonates (gestational age, ≥36 weeks; 217 [51%] female infants), convulsions were not observed, and high-pitched cry and hyperactive Moro reflex had extremely different frequencies across cohorts. Therefore, these 3 FNAST items were removed from further analysis. The 2 tremor items were combined, and 8 of the remaining 17 items were independently associated with pharmacologic treatment, with an area under the curve of 0.86 (95% CI, 0.82-0.89) compared with 0.90 (95% CI, 0.87-0.94) for the 21-item FNAST. External validation of the 8 items resulted in an area under the curve of 0.86 (95% CI, 0.79-0.93). Thresholds of 4 and 5 on the simplified scale yielded the closest agreement with FNAST thresholds of 8 and 12 (weighted κ = 0.55; 95% CI, 0.48-0.61).

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that 8 signs of NAS may be sufficient to assess whether a neonate meets criteria for pharmacologic therapy. A focus on these signs could simplify the FNAST tool and may enhance its clinical utility.

Prenatal Exposures Are Associated With Worse Neurodevelopmental Outcomes in Infants With Neonatal Opioid Withdrawal Syndrome

Aim: To define a developmental trajectory in infants with neonatal opioid withdrawal syndrome (NOWS) and determine whether the impacted developmental domain varies with the type of antenatal exposure. Methods: We performed a retrospective cohort study of infants treated pharmacologically for NOWS and assessed using a standardized schedule for follow-up visits. We compared outcomes of the study population to published norms using one-sample t-tests. Multivariable models examined associations with exposures in addition to opioids. Results: In our cohort of 285 infants with 9-12-months testing, 164 (55.7%) were seen at 3-4 months, and 125 (44%), at 15-18 months. The majority (58%) had intrauterine drug exposures in addition to opioids. Neurodevelopmental scores of infants with NOWS at 3-4 and 9-12 months were not different from published norms. Cognitive and language scores at 15-18 months were worse than published norms. Male sex, older maternal age, and additional barbiturate or alcohol exposure were associated with worse outcomes. Conclusion: Infants with pharmacologically treated NOWS had development similar to unexposed infants during the 1st year but worse cognitive and language scores during the 2nd year. These data support the need for a prospective follow-up of large cohorts of infants with NOWS, with systematic assessments and an evaluation of contributing factors.

Neonatal Abstinence Syndrome: Review of Epidemiology, Care Models, and Current Understanding of Outcomes

The incidence of neonatal abstinence syndrome owing to prenatal opioid exposure has grown rapidly in recent decades and it disproportionately affects rural, non-white, and public insurance-dependent populations. Treatment consists of pharmacologic and nonpharmacologic interventions with wide variability in approaches across the United States. Standardizing clinical assessment, minimizing unnecessary interruptions, and prioritizing nonpharmacologic and family-centered care seems to improve hospital outcomes. Neonatal abstinence syndrome may have long-term developmental and biological effects, but understanding is limited owing in part confounding biosocial factors. Early intervention and longitudinal support of the infant and family promote better outcomes.

Risk Factors Associated with the Occurrence of Neonatal Opioid Withdrawal Syndrome: A Review

In a number of countries, the prevalence of neonatal opioid withdrawal syndrome (NOWS) is increasing. While NOWS is ultimately the result of opioid exposure in utero, a wide range of risk factors have been associated with the prevalence of NOWS, extending beyond just drug exposure. This article reviews the available literature on factors associated with the incidence of NOWS in opioid-exposed neonates. A range of risk factors have been associated with NOWS, including features of neonatal drug exposure, maternal and neonatal characteristics, aspects of labor and delivery, and genetics. Increased length of gestation and higher birth weight were consistently associated with an increased risk of NOWS, while breast feeding and 'rooming-in' were associated with a reduced risk of NOWS. Additionally, several genetic factors have also been associated with NOWS severity. There is conflicting evidence on the association between NOWS and other risk factors including opioid dose, neonate sex, and the use of some medications during pregnancy. This may be in part attributable to differences in how NOWS is diagnosed and the variety of methodologies across studies. While a large number of risk factors associated with NOWS are non-modifiable, encouraging pregnant women to reduce other drug use (including smoking), breast feed their child, and the judicious use of medications during pregnancy may help reduce the prevalence of NOWS. The presence or absence of NOWS in an opioid-exposed neonate is associated with a wide range of factors. Some of these modifiable risk factors may be potential targets for the primary prevention of NOWS.

Association of Punitive and Reporting State Policies Related to Substance Use in Pregnancy With Rates of Neonatal Abstinence Syndrome

IMPORTANCE

Despite the rapidly changing policy environment regarding substance use during pregnancy, information is lacking on the association of state policies with neonatal abstinence syndrome (NAS).

OBJECTIVE

To determine if punitive or reporting state policies related to substance use during pregnancy are associated with NAS rates.

DESIGN, SETTING, AND PARTICIPANTS

This repeated cross-sectional study used retrospective, difference-in-difference analysis of live births in the State Inpatient Databases from 8 US states in varying years between January 1, 2003, and December 31, 2014. States without punitive or reporting policies were compared with states with policies before and after policy enactment using logistic regression models adjusted for individual and county-level factors and state and year fixed effects. Analyses were conducted from April 10, 2019, to July 30, 2019.

EXPOSURES

Time since enactment of state policies related to substance use in pregnancy, county-level rurality and unemployment, and presence of specialized treatment programs for pregnant and postpartum women in a county.

MAIN OUTCOME AND MEASURES

Rates of NAS.

RESULTS

Among 4 567 963 live births, 23 377 neonates (0.5%) received a diagnosis of NAS. Among neonates with NAS, 3394 (14.5%) lived in counties without any treatment programs specifically for pregnant and postpartum women, 20 323 (86.9%) lived in metropolitan counties, and 8135 (34.8%) lived in counties in the highest unemployment quartile. In adjusted analyses among neonates in states with punitive policies, odds of NAS were significantly greater during the first full calendar year after enactment (adjusted odds ratio, 1.25; 95% CI, 1.06-1.46; P = .007) and more than 1 full year after enactment (adjusted odds ratio, 1.33; 95% CI, 1.17-1.51; P < .001). After regression adjustment, the annual NAS rate was 46 (95% CI, 43-48) neonates with NAS per 10 000 live births in states without punitive policies; 57 (95% CI, 48-65) neonates with NAS per 10 000 live births in states with punitive policies during the first full year after enactment; and 60 (95% CI, 56-65) neonates with NAS per 10 000 live births in states with punitive policies in effect for more than 1 full year. There was no association between reporting policies and odds of NAS.

CONCLUSIONS AND RELEVANCE

In this repeated cross-sectional analysis of 8 states, states with punitive policies were associated with greater odds of NAS immediately and in the longer term, but there was no association between NAS and states with reporting policies.

Sex-Dependent Gene Expression in Infants with Neonatal Opioid Withdrawal Syndrome

OBJECTIVES

To evaluate salivary biomarkers that elucidate the molecular mechanisms by which in utero opioid exposure exerts sex-specific effects on select hypothalamic and reward genes driving hyperphagia, a hallmark symptom of infants suffering from neonatal opioid withdrawal syndrome (NOWS).

STUDY DESIGN

We prospectively collected saliva from 50 newborns born at ≥34 weeks of gestational age with prenatal opioid exposure and 50 sex- and gestational age-matched infants without exposure. Saliva underwent transcriptomic analysis for 4 select genes involved in homeostatic and hedonic feeding regulation (neuropeptide Y2 receptor [NPY2R], proopiomelanocortin [POMC], leptin receptor [LEPR], dopamine type 2 receptor [DRD2]). Normalized gene expression data were stratified based on sex and correlated with feeding volume on day of life 7 and length of stay in infants with NOWS requiring pharmacotherapy.

RESULTS

Expression of DRD2, a hedonistic/reward regulator, was significantly higher in male newborns compared with female newborns with NOWS (Δ threshold cycle 10.8 ± 3.8 vs 13.9 ± 3.7, P = .01). In NOWS requiring pharmacotherapy expression of leptin receptor, an appetite suppressor, was higher in male subjects than female subjects (Δ threshold cycle 8.4 ± 2.5 vs 12.4 ± 5.1, P = .05), DRD2 expression significantly correlated with intake volume on day of life 7 (r = 0.58, P = .02), and expression of NPY2R, an appetite regulator, negatively correlated with length of stay (r = -0.24, P = .05).

CONCLUSIONS

Prenatal opioid exposure exerts sex-dependent effects on hypothalamic feeding regulatory genes with clinical correlations. Neonatal salivary gene expression analyses may predict hyperphagia, severity of withdrawal state, and length of stay in infants with NOWS.

Drivers of Hospital Length of Stay in Medicaid and Commercially Insured Mother-Infant Pairs With a Diagnosis of Neonatal Abstinence Syndrome

BACKGROUND

The occurrence of neonatal abstinence syndrome (NAS) mirrors the growing opioid epidemic in the United States. As Medicaid covers a majority of cases, the commercially insured population has largely been ignored for NAS risk.

OBJECTIVE

The objective of this study was to examine Medicaid and commercially insured mother-infant pairs to determine demographic and clinical characteristics associated with NAS length of stay (LOS).

RESEARCH DESIGN

This observational, descriptive case-series study utilized administrative claims from HealthCore Integrated Research Database to measure maternal characteristics for 6 months before delivery, and neonatal characteristics and health care service utilization for 3 months after NAS diagnosis. Bootstrapped regressions were used to model LOS.

RESULTS

The sample included 1807 mother-infant pairs. Most infants (79%) had Medicaid coverage (Medicaid: N=1419; Commercial: N=388). Although all infants had NAS, Medicaid-insured mothers had more prevalent drug abuse (70.8% vs. 41.0%; P<0.0001), but fewer used prescription opioids (45.3% vs. 60.8%; P<0.0001) compared with commercially insured mothers. Commercially insured infants were sicker, with a higher prevalence of complex chronic conditions, and yet Medicaid-insured infants were admitted to neonatal intensive care unit at a much higher rate (91.1% vs. 78.9%; P<0.0001). After adjustment, neonatal intensive care unit admission (+6.7 d, 95% confidence interval: 4.5-9.3) and chronic complex conditions (+5.2 d, 95% confidence interval: 3.8-6.6) contributed most to LOS.

CONCLUSION

A re-evaluation of obstetrical management towards a focus on the history of possible opioid and substance use regardless of insurance type and demographic background might inform efforts to reduce LOS.

Surveillance, Epidemiology, and Estimated Burden of Neonatal Abstinence Syndrome, Tennessee, 2013-2016

OBJECTIVES

Between 2003 and 2013, the rate of neonatal abstinence syndrome (NAS)-a postnatal drug withdrawal syndrome-in Tennessee increased approximately 10-fold. NAS surveillance is relatively new, and underestimation associated with surveillance has not been described. We compared data from the Tennessee NAS public health surveillance system (TNSS) with a second source of NAS data, hospital discharge data system (HDDS), and estimated the true number of infants with NAS using capture-recapture methods.

METHODS

We obtained NAS data on cases of NAS among Tennessee infants from TNSS and HDDS from January 1, 2013, through December 31, 2016. We matched cases of NAS identified in TNSS to cases identified in HDDS. We estimated the true number of infants with NAS by using the Lincoln-Peterson estimator capture-recapture methodology.

RESULTS

During the study period, 4070 infants with NAS were reported to TNSS, and 5321 infants with NAS were identified in HDDS; 2757 were in both data sets. Using capture-recapture methods, the total estimated number of infants with NAS during the study period was 7855 (annual mean = 1972; estimated range = 1531-2427), which was 93% more than in TNSS and 48% more than in HDDS. Drugs used for the medication-assisted treatment of substance use disorder were the most commonly reported substances associated with NAS (n = 2389, 59%).

CONCLUSIONS

TNSS underestimated the total burden of NAS based on the capture-recapture estimate. Case-based public health surveillance is important for monitoring the burden of and risk factors for NAS and helping guide public health interventions.

Maternal hair cortisol levels as a novel predictor of neonatal abstinence syndrome severity: A pilot feasibility study

Neonatal abstinence syndrome (NAS) after in-utero opioid exposure remains a poorly understood condition with multiple factors contributing to severity. Exposure to maternal stress may be one contributing factor. Hair cortisol measurement represents a novel technique for assessing prenatal stress. In this pilot study, the association between maternal hair cortisol levels and NAS severity was examined in 70 postpartum women with opioid use disorder within 72 hr of delivery. Infants were monitored for NAS and treated according to institutional protocol. Forty-four (63%) of the infants were pharmacologically treated for NAS, with a mean length of hospital stay (LOS) for all infants of 14.2 (SD 9.0) days. The mean cortisol level in the mothers was 131.8 pg/mg (SD 124.7). In bivariate analysis, higher maternal hair cortisol levels were associated with shorter infant LOS (R = -.26, p = .03) and fewer infant opioid treatment days (R = -.28, p = .02). Results were no longer statistically significant in regression models after adjusting for maternal opioid and smoking. In conclusion, we demonstrated the feasibility of hair cortisol assaying within the first few days after delivery in mothers with opioid use disorder as a novel marker for NAS. The findings suggest that maternal stress may impact the severity of infant opioid withdrawal.

Increased Severity of Neonatal Abstinence Syndrome Associated With Concomitant Antenatal Opioid and Benzodiazepine Exposure

BACKGROUND

Polysubstance use is common among opioid-using women, yet its association with pharmacotherapy for neonatal abstinence syndrome (NAS) remains unclear. We hypothesized that benzodiazepine exposure would increase risk of an infant developing pharmacologically treated NAS.

METHODS

We conducted a retrospective cohort study of maternal-infant dyads enrolled in Tennessee Medicaid, using individual-level data linkage of vital records and administrative (ie, outpatient, inpatient, and prescription) data from 2009 to 2011. These data underwent chart review from 2013 to 2016 to obtain clinically relevant exposure data (eg, toxicology testing). The association of antenatal exposures with pharmacologically treated NAS was evaluated by using multivariable logistic regression, controlling for maternal and infant factors and clustered by hospital.

RESULTS

Among 112 029 maternal-infant dyads, we confirmed 822 cases of NAS, of which 598 (72.7%) were cases of pharmacologically treated NAS. Infants who developed pharmacologically treated NAS were more likely to have been exposed to antenatal benzodiazepines compared with infants with confirmed NAS not treated pharmacologically (40.9% vs 30.8%; P = .008). In adjusted analyses, benzodiazepine exposure was associated with greater risk of developing pharmacologically treated NAS (odds ratio: 1.51; 95% confidence interval: 1.04-2.21). Alternatively, exposure to tobacco, marijuana, cocaine, gabapentin, and selective serotonin reuptake inhibitors were not associated with increased risk of developing pharmacologically treated NAS.

CONCLUSIONS

Among a population of infants with intrauterine polysubstance exposure, benzodiazepine exposure was an independent predictor of an infant developing pharmacologically treated NAS. Obtaining history of antenatal benzodiazepine exposure among opioid-exposed infants may allow for risk stratification and development of personalized care plans.

Novel biomarkers to assess in utero effects of maternal opioid use: First steps toward understanding short- and long-term neurodevelopmental sequelae

Maternal opioid use disorder is common, resulting in significant neonatal morbidity and cost. Currently, it is not possible to predict which opioid-exposed newborns will require pharmacotherapy for neonatal abstinence syndrome. Further, little is known regarding the effects of maternal opioid use disorder on the developing human brain. We hypothesized that novel methodologies utilizing fetal central nervous system-derived extracellular vesicles isolated from maternal blood can address these gaps in knowledge. Plasma from opioid users and controls between 9 and 21 weeks was precipitated and extracellular vesicles were isolated. Mu opioid and cannabinoid receptor levels were quantified. Label-free proteomics studies and unbiased small RNA next generation sequencing was performed in paired fetal brain tissue. Maternal opioid use disorder increased mu opioid receptor protein levels in extracellular vesicles independent of opioid equivalent dose. Moreover, cannabinoid receptor levels in extracellular vesicles were upregulated with opioid exposure indicating cross talk with endocannabinoids. Maternal opioid use disorder was associated with significant changes in extracellular vesicle protein cargo and fetal brain micro RNA expression, especially in male fetuses. Many of the altered cargo molecules and micro RNAs identified are associated with adverse clinical neurodevelopmental outcomes. Our data suggest that assays relying on extracellular vesicles isolated from maternal blood extracellular vesicles may provide information regarding fetal response to opioids in the setting of maternal opioid use disorder. Prospective clinical studies are needed to evaluate the association between extracellular vesicle biomarkers, risk of neonatal abstinence syndrome and neurodevelopmental outcomes.

How Might Maternal Poverty Impact the Course of Neonatal Opioid Withdrawal Syndrome?

: Neonatal Opioid Withdrawal Syndrome (NOWS) is an increasing problem in the midst of the current opioid epidemic, frequently associated with pharmacologic treatment and prolonged hospitalizations. NOWS is a highly variable condition with many clinical and genetic variables contributing to the clinical course. Social variables such as maternal poverty remain understudied. In this commentary, we review one of the first studies of the association between maternal poverty and infant hospital length of stay in infants with NOWS. This has important implications for designing population level interventions to improve NOWS outcomes.

Optimal Timing to Utilize Olfactory Stimulation with Maternal Breast Milk to Improve Oral Feeding Skills in the Premature Newborn

Background: Olfactory maturation is essential for successful oral feeding. Previous studies have suggested that olfactory stimulation with maternal breast milk may expedite oral feeding skills in the premature infant; however, the optimal developmental window to utilize this intervention and sex-specific responses to stimuli are largely unknown. Objectives: To determine individual responses to olfactory stimulation with mother's own milk (MOM) on feeding outcomes in premature newborns. Materials and Methods: Infants born between 28 0/7 and 33 6/7 weeks' gestation (n = 36) were randomized to receive either MOM or water (sham) stimulus during the learning process of oral feeding. Clinical and feeding outcomes were recorded. Statistical analyses examined the effect of stimulation with MOM on feeding outcomes stratified for age and sex. Results: Overall, there was no significant difference between sham infants compared with MOM infants in mean postmenstrual age of full oral feeds (sham: 35 5/7 versus MOM 36 0/7; p = 0.37). However, when stratified by gestational age (GA), infants born <31 weeks' gestation who received MOM stimulation learned to feed sooner than controls (p = 0.06), whereas infants born ≥31 weeks' gestation learned to feed later than controls (p = 0.20) with a significant interaction (p = 0.02) between the stimulus (MOM versus sham) and dichotomized GA (<31 versus ≥31 weeks). There were no sex differences in response to olfactory stimulus. Conclusions: Infants born <31 weeks' GA who received MOM stimulation learned to feed sooner than control infants and the impact of MOM is significantly different between infants born before or after 31 weeks GA. These data suggest there may be an optimal time in development to utilize maternal breast milk to expedite oral feeding maturation in the premature newborn.