Do maternal opioids reduce neonatal regional brain volumes? A pilot study

Antenatal Opioid Exposure and Global and Regional Brain Volumes in Newborns

Importance

Although antenatal opioid exposure is associated with impaired brain growth, previous studies are limited by small sample sizes and lack of controls. As a result, the impacts of opioid exposure on the developing brain remain poorly understood.

Objective

To compare global, regional, and tissue-specific brain volumes in opioid-exposed newborns vs unexposed controls.

Design, Setting, and Participants

In the OBOE (Outcomes of Babies with Opioid Exposure) study, term newborns with antenatal opioid exposure and unexposed controls were recruited at 4 sites in the US from August 2020 to December 2023. Data analysis was performed from August 2020 to December 2024.

Main Outcomes and Measures

The primary outcome was brain volumes in both groups, assessed via unsedated 3-dimensional (3-D) volumetric magnetic resonance imaging (MRI) in opioid-exposed and unexposed newborns prior to 8 weeks of age. T2-weighted MRI data were acquired on Siemens and Philips 3T scanners and harmonized across sites. Brains were segmented using DrawEM- and 3D U-Net-based pipelines and manual corrections. Brain volumes were compared between groups using analysis of covariance, adjusting for postmenstrual age at MRI, sex, birth weight, maternal smoking, and maternal education.

Results

A total of 173 newborns with antenatal opioid exposure and 96 unexposed controls were studied. MRIs were performed at a mean (SD) age of 42.84 (2.11) postmenstrual weeks, and 117 newborns (43.5%) were female. The opioid-exposed group had significantly smaller total brain volume (387.51 vs 407.06 cm3; difference, 19.55; 95% CI, 8.75-30.35) and cortical (167.07 vs 176.35 cm3; difference, 9.28; 95% CI, 3.86-14.70), deep gray matter (27.22 vs 28.76 cm3; difference, 1.54; 95% CI, 0.66-2.43), white matter (159.90 vs 166.65 cm3; difference, 6.76; 95% CI, 1.71-11.81), cerebellar (23.47 vs 24.99 cm3; difference, 1.52; 95% CI, 0.67-2.36), brainstem (6.80 vs 7.18 cm3; difference, 0.38; 95% CI, 0.19-0.57), and amygdala volumes (left: 0.48 vs 0.51 cm3; difference, 0.03; 95% CI, 0.004-0.05; right: 0.51 vs 0.55 cm3; difference, 0.04; 95% CI, 0.08-0.07) compared to controls. Methadone-exposed newborns showed significantly smaller white matter volume compared to controls, while buprenorphine-exposed newborns showed significantly smaller right amygdala volume than controls. Compared to controls, newborns exposed to opioids only and those exposed to opioids plus other substances both showed significant reductions in volumes of cortical and deep gray matter, cerebellum, brainstem, right amygdala, and total brain. Polysubstance-exposed newborns additionally showed smaller volumes in white matter and the left amygdala compared to controls.

Conclusions and Relevance

In a large cohort of antenatally opioid-exposed newborns, there were significant reductions in global and regional brain volumes compared to unexposed controls. These data suggest vulnerability of the developing brain to antenatal opioid exposure, with varying effects depending on the type and number of substances.

Trial Registration

ClinicalTrials.gov Identifier: NCT04149509.

Head Ultrasound Findings in Infants with Birth Weight >1,500 g and Gestational Age >32 Weeks Exposed to Prenatal Opioids

This study aimed to evaluate the effects of prenatal exposure to opioids on head ultrasound (HUS) and to determine the need for routine HUS evaluation in infants exposed to prenatal opioids.This is a retrospective cohort study performed at a level III NICU. Infants >32 weeks gestational age and >1,500 g birth weight with prenatal opioid exposure (n = 127) were included in this study. Data including demographic information and HUS results were recorded.Twenty (16%) infants were exposed to opioids only whereas the rest of the infants (84%) were exposed to opioids plus other drugs (polysubstance) in utero. Sixteen of 127 infants (13%) had abnormal initial HUS. Sub-ependymal hemorrhage or grade 1 intraventricular hemorrhage was the most common abnormal finding. Absent septum pellucidum was seen in three infants.A relatively large proportion (13%) of infants in this study had abnormal HUS findings; however, further studies are required to correlate HUS findings with a specific drug of exposure, duration of exposure, polysubstance use, umbilical cord drug concentration levels, and neurodevelopmental outcomes. · Limited data exists regarding HUS findings in infants with prenatal opioid exposure.. · A relatively large proportion of infants exposed to opioids in utero had abnormal HUS.. · Subependymal hemorrhages or grade I intraventricular hemorrhage was the most common abnormal finding..

Children had smaller brain volumes and cortical surface areas after prenatal opioid maintenance therapy exposure

AIM

The studies have shown that infants with prenatal OMT exposure had smaller brain volumes than non-exposed controls, but long-term outcome data are lacking. We examined 5-13-year-old OMT-exposed children with brain MRI and tested motor and visual-motor functions and possible associations between brain morphology and outcome.

METHODS

To this retrospective cohort study, we recruited 55 children with prenatal OMT exposure and 59 age- and gender-matched controls. They were examined with brain MRI, Movement-ABC and Beery-VMI. MRI images were processed with the Free Surfer® software to obtain volumetrics and estimates of cortical surface area and thickness. We used a general linear regression model (GLM) to calculate group differences.

RESULTS

The children in the OMT group had smaller mean total intracranial volume (ICV), 1407 cm3 (CI 95% 1379-1434) versus 1450 cm3 (CI 95% 1423-1476) in the control group (p = 0.026). After adjusting for ICV, significant group differences persisted for volumes of amygdala, basal ganglia and mid-posterior part of corpus callosum. Cortical surface area was smaller in the left caudal middle frontal gyrus and the right inferior parietal lobule in the OMT-group. Visual-motor function was significantly correlated with ICV.

CONCLUSION

Prenatal OMT exposure may alter early brain development with possible negative long-term functional consequences.

Impact of Intrauterine Insults on Fetal and Postnatal Cerebellar Development in Humans and Rodents

Many children suffer from neurodevelopmental aberrations that have long-term effects. To understand the consequences of pathological processes during particular periods in neurodevelopment, one has to understand the differences in the developmental timelines of brain regions. The cerebellum is one of the first brain structures to differentiate during development but one of the last to achieve maturity. This relatively long period of development underscores its vulnerability to detrimental environmental exposures throughout gestation. Moreover, as postnatal functionality of the cerebellum is multifaceted, enveloping sensorimotor, cognitive, and emotional domains, prenatal disruptions in cerebellar development can result in a large variety of neurological and mental health disorders. Here, we review major intrauterine insults that affect cerebellar development in both humans and rodents, ranging from abuse of toxic chemical agents, such as alcohol, nicotine, cannabis, and opioids, to stress, malnutrition, and infections. Understanding these pathological mechanisms in the context of the different stages of cerebellar development in humans and rodents can help us to identify critical and vulnerable periods and thereby prevent the risk of associated prenatal and early postnatal damage that can lead to lifelong neurological and cognitive disabilities. The aim of the review is to raise awareness and to provide information for obstetricians and other healthcare professionals to eventually design strategies for preventing or rescuing related neurodevelopmental disorders.

Improving neurological and mental health outcomes for children with prenatal drug exposure

Prenatal drug exposure is a global public health problem that will never be completely eliminated. Some drugs are essential for maternal health but many others are used recreationally and for non-medical reasons. Both legal and illegal drugs of addiction and dependency have the potential to cause permanent and even intergenerational harm to the developing child and understanding the direct impact of drugs of addiction on child neurodevelopmental and mental health is difficult and confounded by many social, environmental and possibly, genetic factors. Furthermore, many drugs are not clear neuroteratogens and their impact on the child may be indolent and not appreciated for a long time after exposure has occurred. Despite this, there are numerous windows of opportunity to improve the eventual outcomes of the child including utilising the enormous benefits of neuroplasticity and general principles of basic health care and support. This chapter will discuss current understanding of the impact of drugs of addiction on the growing child and offer possible mitigation strategies to improve outcomes.

Ultrasound evaluation of brain parenchyma in preterm infants with prenatal opioid exposure

OBJECTIVE

To evaluate whether preterm infants with prenatal opioid exposure had differences in brain size on head ultrasounds (HUS) in comparison to non-exposed infants.

STUDY DESIGN

Preterm infants ≤34 weeks with prenatal opioid exposure (n = 47) and matched non-exposed infants (n = 62) with early HUSs were examined. Fifteen brain measurements were made and linear regression models performed to evaluate differences.

RESULTS

Brain measurements were smaller in the right ventricular index [β = -0.18 mm (95% CI -0.32, -0.03]), left ventricular index [β = -0.04 mm (95% CI -0.08, -0.003)], left basal ganglia insula [β = -0.10 mm (95% CI -0.15, -0.04)], right basal ganglia insula [β = -0.08 mm (95% CI -0.14, -0.03)], corpus callosum fastigium length [β = -0.16 mm (95% CI -0.25, -0.06)], intracranial height index [β = -0.31 mm (95% CI -0.44, -0.18)], and transcerebellar measurements [β = -0.13 (95% CI -0.25, -0.02)] in the opioid-exposed group.

CONCLUSIONS

Preterm infants with prenatal opioid exposure have smaller brain sizes compared to non-exposed infants, potentially increasing their risk for neurodevelopmental abnormalities.

Intrauterine exposure to maternal opioid maintenance treatment and associated risk factors may impair child growth

AIM

How maternal opioid maintenance treatment (OMT) affects children is under-researched. This population-based registry study investigated child growth and somatic health following intrauterine exposure to this treatment.

METHODS

Children born between 1 March 2011 and 30 May 2021 to mothers who used buprenorphine, buprenorphine-naloxone, or methadone throughout their pregnancies were followed for 2 years at the Helsinki University Hospital, Finland. Appropriate statistical tests were used to compare the treatment groups.

RESULTS

Of the 67 neonates, 52% were male, 96% were born full-term and 63% were treated for neonatal opioid withdrawal syndrome. Otherwise, the children were predominantly healthy, although relatively small: 22% were small for gestational age, the methadone group children being the smallest. Foetal exposure to maternal methadone treatment, illicit drugs, hepatitis C and smoking were associated with small for gestational age; the former two were also associated with later slower growth, especially head growth and weight gain (p < 0.001). However, 29% were overweight at 2 years.

CONCLUSION

Using child growth as the outcome, we found that buprenorphine-naloxone and buprenorphine-monotherapy had equal effects as forms of maternal OMT. Exposure to multiple risk factors may harm foetal and subsequent growth. We recommend long-term follow-up of children exposed to maternal OMT.

Neural and behavioral indicators of cognitive control in preschoolers with and without prenatal opioid exposure

Prenatal opioid exposure is one consequence of the opioid epidemic, but effects on child development remain poorly understood. There is emerging evidence that children exposed to opioids in utero exhibit elevated emotional and behavioral problems, which may be partially due to alterations in cognitive control. Using multiple methods (i.e., neuropsychological, behavioral, and event-related potential [ERP] assessments), the present study examined differences in emotional, behavioral, and cognitive control difficulties in preschool-aged children with (n = 21) and without (n = 23) prenatal opioid exposure (Mage = 4.30, SD = 0.77 years). Child emotional and behavioral problems were measured with a caregiver questionnaire, indicators of cognitive control were measured using developmentally appropriate behavioral (i.e., delay discounting, Go/No-Go) and neuropsychological (i.e., Statue) tasks, and electroencephalogram was recorded to error and correct responses in a Go/No-Go task. ERP analyses focused on the error-related negativity (ERN), an ERP that reflects error monitoring, and correct-response negativity (CRN), a component reflecting performance monitoring more generally. Opioid exposure was associated with elevated difficulties across domains and a blunted ERN, reflecting altered cognitive control at the neural level, but groups did not significantly differ on behavioral measures of cognitive control. These result replicate prior studies indicating an association between prenatal opioid exposure and behavioral problems in preschool-aged children. Further, our findings suggest these differences may be partially due to children with prenatal opioid exposure exhibiting difficulties with cognitive control at the neural level. The ERN is a potential target for future research and intervention efforts to address the sequelae of prenatal opioid exposure.

Development, Insults and Predisposing Factors of the Brain's Predictive Coding System to Chronic Perceptual Disorders-A Life-Course Examination

The predictive coding theory is currently widely accepted as the theoretical basis of perception and chronic perceptual disorders are explained as the maladaptive compensation of the brain to a prediction error. Although this gives us a general framework to work with, it is still not clear who may be more susceptible and/or vulnerable to aberrations in this system. In this paper, we study changes in predictive coding through the lens of tinnitus and pain. We take a step back to understand how the predictive coding system develops from infancy, what are the different neural and bio markers that characterise this system in the acute, transition and chronic phases and what may be the factors that pose a risk to the aberration of this system. Through this paper, we aim to identify people who may be at a higher risk of developing chronic perceptual disorders as a reflection of aberrant predictive coding, thereby giving future studies more facets to incorporate in their investigation of early markers of tinnitus, pain and other disorders of predictive coding. We therefore view this paper to encourage the thinking behind the development of preclinical biomarkers to maladaptive predictive coding.

Neonatal opioid toxicity: opioid withdrawal (abstinence) syndrome with emphasis on pharmacogenomics and respiratory depression

The increasing use of opioids in pregnant women has led to an alarming rise in the number of cases of neonates with drug-induced withdrawal symptoms known as neonatal opioid withdrawal syndrome (NOWS). NOWS is a toxic heterogeneous condition with many neurologic, autonomic, and gastrointestinal symptoms including poor feeding, irritability, tachycardia, hypertension, respiratory defects, tremors, hyperthermia, and weight loss. Paradoxically, for the management of NOWS, low doses of morphine, methadone, or buprenorphine are administered. NOWS is a polygenic disorder supported by studies of genomic variation in opioid-related genes. Single-nucleotide polymorphisms (SNPs) in CYP2B6 are associated with variations in NOWS infant responses to methadone and SNPs in the OPRM1, ABCB1, and COMT genes are associated with need for treatment and length of hospital stay. Epigenetic gene changes showing higher methylation levels in infants and mothers have been associated with more pharmacologic treatment in the case of newborns, and for mothers, longer infant hospital stays. Respiratory disturbances associated with NOWS are not well characterized. Little is known about the effects of opioids on developing neonatal respiratory control and respiratory distress (RD), a potential problem for survival of the neonate. In a rat model to test the effect of maternal opioids on the developing respiratory network and neonatal breathing, maternal-derived methadone increased apneas and lessened RD in neonates at postnatal (P) days P0 and P1. From P3, breathing normalized with age suggesting reorganization of respiratory rhythm-generating circuits at a time when the preBötC becomes the dominant inspiratory rhythm generator. In medullary slices containing the preBötC, maternal opioid treatment plus exposure to exogenous opioids showed respiratory activity was maintained in younger but not older neonates. Thus, maternal opioids blunt centrally controlled respiratory frequency responses to exogenous opioids in an age-dependent manner. In the absence of maternal opioid treatment, exogenous opioids abolished burst frequencies at all ages. Prenatal opioid exposure in children stunts growth rate and development while studies of behavior and cognitive ability reveal poor performances. In adults, high rates of attention deficit disorder, hyperactivity, substance abuse, and poor performances in intelligence and memory tests have been reported.

Decreased myelin-related gene expression in the nucleus accumbens during spontaneous neonatal opioid withdrawal in the absence of long-term behavioral effects in adult outbred CFW mice

Prenatal opioid exposure is a major health concern in the United States, with the incidence of neonatal opioid withdrawal syndrome (NOWS) escalating in recent years. NOWS occurs upon cessation of in utero opioid exposure and is characterized by increased irritability, disrupted sleep patterns, high-pitched crying, and dysregulated feeding. The main pharmacological strategy for alleviating symptoms is treatment with replacement opioids. The neural mechanisms mediating NOWS and the long-term neurobehavioral effects are poorly understood. We used a third trimester-approximate model in which neonatal outbred pups (Carworth Farms White; CFW) were administered once-daily morphine (15 mg/kg, s.c.) from postnatal day (P) day 1 through P14 and were then assessed for behavioral and transcriptomic adaptations within the nucleus accumbens (NAc) on P15. We also investigated the long-term effects of perinatal morphine exposure on adult learning and reward sensitivity. We observed significant weight deficits, spontaneous thermal hyperalgesia, and altered ultrasonic vocalization (USV) profiles following repeated morphine and during spontaneous withdrawal. Transcriptome analysis of NAc from opioid-withdrawn P15 neonates via bulk mRNA sequencing identified an enrichment profile consistent with downregulation of myelin-associated transcripts. Despite the neonatal behavioral and molecular effects, there were no significant long-term effects of perinatal morphine exposure on adult spatial memory function in the Barnes Maze, emotional learning in fear conditioning, or in baseline or methamphetamine-potentiated reward sensitivity as measured via intracranial self-stimulation. Thus, the once daily third trimester-approximate exposure regimen, while inducing NOWS model traits and significant transcriptomic effects in neonates, had no significant long-term effects on adult behaviors.

HIGHLIGHTS

We replicated some NOWS model traits via 1x-daily morphine (P1-P14).We found a downregulation of myelination genes in nucleus accumbens on P15.There were no effects on learning/memory or reward sensitivity in adults.

Outcomes of Babies with Opioid Exposure (OBOE): protocol of a prospective longitudinal cohort study

BACKGROUND

While the health, social, and economic impacts of opioid addiction on adults and their communities are well known, the impact of maternal opioid use on the fetus exposed in utero is less well understood.

METHODS

This paper presents the protocol of the ACT NOW Outcomes of Babies with Opioid Exposure (OBOE) Study, a multi-site prospective longitudinal cohort study of infants with antenatal opioid exposure and unexposed controls. Study objectives are to determine the impact of antenatal opioid exposure on brain development and neurodevelopmental outcomes over the first 2 years of life and explore whether family, home, and community factors modify developmental trajectories during this critical time period.

RESULTS

Primary outcomes related to brain development include cortical volumes, deep cerebral gray matter volumes, resting-state functional connectivity measures, and structural connectivity measures using diffusion tensor imaging. Primary neurodevelopmental outcomes include visual abnormalities, cognitive, language, and motor skills measured using the Bayley Scales of Infant Development and social-emotional and behavioral problems and competence measured by the Brief Infant-Toddler Social and Emotional Assessment.

CONCLUSIONS

The OBOE study has been designed to overcome challenges of previous studies and will help further understanding of the effects of antenatal opioid exposure on early infant development.

IMPACT

This study will integrate MRI findings and comprehensive neurodevelopmental assessments to provide early insights into the functional topography of the brain in this high-risk population and assess MRI as a potential biomarker. Rather than conducting neuroimaging at a single time point, the study will include serial MRI assessments from birth to 2 years, allowing for the examination of trajectories throughout this period of rapid brain development. While previous studies often have had limited information on exposures, this study will use umbilical cord assays to accurately measure amounts of opioids and other substances from 20 weeks of gestation to birth.

Shaping the risk for late-life neurodegenerative disease: A systematic review on prenatal risk factors for Alzheimer's disease-related volumetric brain biomarkers

Environmental exposures including toxins and nutrition may hamper the developing brain in utero, limiting the brain's reserve capacity and increasing the risk for Alzheimer's disease (AD). The purpose of this systematic review is to summarize all currently available evidence for the association between prenatal exposures and AD-related volumetric brain biomarkers. We systematically searched MEDLINE and Embase for studies in humans reporting on associations between prenatal exposure(s) and AD-related volumetric brain biomarkers, including whole brain volume (WBV), hippocampal volume (HV) and/or temporal lobe volume (TLV) measured with structural magnetic resonance imaging (PROSPERO; CRD42020169317). Risk of bias was assessed using the Newcastle Ottawa Scale. We identified 79 eligible studies (search date: August 30th, 2020; Ntotal=24,784; median age 10.7 years) reporting on WBV (N = 38), HV (N = 63) and/or TLV (N = 5) in exposure categories alcohol (N = 30), smoking (N = 7), illicit drugs (N = 14), mental health problems (N = 7), diet (N = 8), disease, treatment and physiology (N = 10), infections (N = 6) and environmental exposures (N = 3). Overall risk of bias was low. Prenatal exposure to alcohol, opioids, cocaine, nutrient shortage, placental dysfunction and maternal anemia was associated with smaller brain volumes. We conclude that the prenatal environment is important in shaping the risk for late-life neurodegenerative disease.

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.

Prenatal heroin exposure alters brain morphology and connectivity in adolescent mice

The United States is experiencing a dramatic increase in maternal opioid misuse and, consequently, the number of individuals exposed to opioids in utero. Prenatal opioid exposure has both acute and long-lasting effects on health and wellbeing. Effects on the brain, often identified at school age, manifest as cognitive impairment, attention deficit, and reduced scholastic achievement. The neurobiological basis for these effects is poorly understood. Here, we examine how in utero exposure to heroin affects brain development into early adolescence in a mouse model. Pregnant C57BL/6J mice received escalating doses of heroin twice daily on gestational days 4-18. The brains of offspring were assessed on postnatal day 28 using 9.4 T diffusion MRI of postmortem specimens at 36 μm resolution. Whole-brain volumes and the volumes of 166 bilateral regions were compared between heroin-exposed and control offspring. We identified a reduction in whole-brain volume in heroin-exposed offspring and heroin-associated volume changes in 29 regions after standardizing for whole-brain volume. Regions with bilaterally reduced standardized volumes in heroin-exposed offspring relative to controls include the ectorhinal and insular cortices. Regions with bilaterally increased standardized volumes in heroin-exposed offspring relative to controls include the periaqueductal gray, septal region, striatum, and hypothalamus. Leveraging microscopic resolution diffusion tensor imaging and precise regional parcellation, we generated whole-brain structural MRI diffusion connectomes. Using a dimension reduction approach with multivariate analysis of variance to assess group differences in the connectome, we found that in utero heroin exposure altered structure-based connectivity of the left septal region and the region that acts as a hub for limbic regulatory actions. Consistent with clinical evidence, our findings suggest that prenatal opioid exposure may have effects on brain morphology, connectivity, and, consequently, function that persist into adolescence. This work expands our understanding of the risks associated with opioid misuse during pregnancy and identifies biomarkers that may facilitate diagnosis and treatment.

Prenatal Opioid Exposure and Neurodevelopmental Outcomes

The opioid epidemic in the United States has resulted in a significant increase in opioid use disorder among pregnant women and a concomitant increase in the incidence of neonatal opioid withdrawal syndrome. The long-term consequences of prenatal opioid exposure on neurodevelopmental outcomes are not fully understood. Animal studies indicate increased neuronal apoptosis and decreased neuronal proliferation and myelination with opioid exposure in-utero. Meta-analyses of human studies suggest decreased cognition and psychomotor performance in infancy and deficits in cognition and language in preschool. However, current studies have primarily focused on heroin or methadone exposure and have been limited by small sample size, inadequate comparison groups, and the inability to account for additional risk factors and exposures such as polysubstance abuse, poor prenatal care, neonatal withdrawal and treatment with opioids, and unsupportive home environment. Future studies should aim to better understand the potential impact of these confounding factors on the neurodevelopmental trajectory of exposed infants. This review discusses the up-to-date literature, current gaps in knowledge, and considerations for future studies in the arena of prenatal opioid exposure and neurodevelopmental outcomes.

Body size and brain volumetry in the rat following prolonged morphine administration in infancy and adulthood

Background

Prolonged morphine treatment in infancy is associated with a high incidence of opioid tolerance and dependence, but our knowledge of the long-term consequences of this treatment is sparse. Using a rodent model, we examined the (1) short- and (2) long-term effects of prolonged morphine administration in infancy on body weight and brain volume, and (3) we evaluated if subsequent dosing in adulthood poses an increased brain vulnerability.

Methods

Newborn rats received subcutaneous injections of either morphine or equal volume of saline twice daily for the first two weeks of life. In adulthood, animals received an additional two weeks of saline or morphine injections before undergoing structural brain MRI. After completion of treatment, structural T2-weigthed MRI images were acquired on a 7 T preclinical scanner (Bruker) using a RARE FSE sequence. Total and regional brain volumes were manually extracted from the MRI images using ITK-SNAP (v.3.6). Regions of interest included the brainstem, the cerebellum, as well as the forebrain and its components: the cerebral cortex, hippocampus, and deep gray matter (including basal ganglia, thalamus, hypothalamus, ventral tegmental area). Absolute (cm³) and normalized (as % total brain volume) values were compared using a one-way ANOVA with Tukey HSD post-hoc test.

Results

Prolonged morphine administration in infancy was associated with lower body weight and globally smaller brain volumes, which was not different between the sexes. In adulthood, females had lower body weights than males, but no difference was observed in brain volumes between treatment groups. Our results are suggestive of no long-term effect of prolonged morphine treatment in infancy with respect to body weight and brain size in either sex. Interestingly, prolonged morphine administration in adulthood was associated with smaller brain volumes that differed by sex only in case of previous exposure to morphine in infancy. Specifically, we report significantly smaller total brain volume of female rats on account of decreased volumes of forebrain and cortex.

Conclusions

Our study provides insight into the short- and long-term consequences of prolonged morphine administration in an infant rat model and suggests brain vulnerability to subsequent exposure in adulthood that might differ with sex.

The immediate and long-term effects of prenatal opioid exposure

The opioid epidemic has adversely affected neonates and children, yet the mechanisms by which it impacts this population are not well understood. Not only does prenatal opioid exposure result in short-term consequences shortly after birth, it also creates long-term sequelae that may predispose these children to physical, emotional, psychiatric, cognitive, and socioeconomic problems in the future. This article provides a scoping overview of the long-term effects of antenatal opioid exposure on neonates and children as well as quality improvement and research efforts to understand and mitigate this major public health concern.

Alterations of brain microstructures in a mouse model of prenatal opioid exposure detected by diffusion MRI

Growing opioid use among pregnant women is fueling a crisis of infants born with prenatal opioid exposure. A large body of research has been devoted to studying the management of opioid withdrawal during the neonatal period in these infants, but less substantive work has explored the long-term impact of prenatal opioid exposure on neurodevelopment. Using a translationally relevant mouse model of prenatal methadone exposure (PME), the aim of the study is to investigate the cerebral microstructural differences between the mice with PME and prenatal saline exposure (PSE). The brains of eight-week-old male offspring with either PME (n = 15) or PSE (n = 15) were imaged using high resolution in-vivo diffusion magnetic resonance imaging on a 9.4 Tesla small animal scanner. Brain microstructure was characterized using diffusion tensor imaging (DTI) and Bingham neurite orientation dispersion and density imaging (Bingham-NODDI). Voxel-based analysis (VBA) was performed using the calculated microstructural parametric maps. The VBA showed significant (p < 0.05) bilateral alterations in fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD), orientation dispersion index (ODI) and dispersion anisotropy index (DAI) across several cortical and subcortical regions, compared to PSE. Particularly, in PME offspring, FA, MD and AD were significantly higher in the hippocampus, dorsal amygdala, thalamus, septal nuclei, dorsal striatum and nucleus accumbens. These DTI-based results suggest widespread bilateral microstructural alterations across cortical and subcortical regions in PME offspring. Consistent with the observations in DTI, Bingham-NODDI derived ODI exhibited significant reduction in PME offspring within the hippocampus, dorsal striatum and cortex. NODDI-based results further suggest reduction in dendritic arborization in PME offspring across multiple cortical and subcortical regions. To our best knowledge, this is the first study of prenatal opioid exposure to examine microstructural organization in vivo. Our findings demonstrate perturbed microstructural complexity in cortical and subcortical regions persisting into early adulthood which could interfere with critical neurodevelopmental processes in individuals with prenatal opioid exposure.

Brain structural connectome in neonates with prenatal opioid exposure

Introduction

Infants with prenatal opioid exposure (POE) are shown to be at risk for poor long-term neurobehavioral and cognitive outcomes. Early detection of brain developmental alterations on neuroimaging could help in understanding the effect of opioids on the developing brain. Recent studies have shown altered brain functional network connectivity through the application of graph theoretical modeling, in infants with POE. In this study, we assess global brain structural connectivity through diffusion tensor imaging (DTI) metrics and apply graph theoretical modeling to brain structural connectivity in infants with POE.

Methods

In this prospective observational study in infants with POE and control infants, brain MRI including DTI was performed before completion of 3 months corrected postmenstrual age. Tractography was performed on the whole brain using a deterministic fiber tracking algorithm. Pairwise connectivity and network measure were calculated based on fiber count and fractional anisotropy (FA) values. Graph theoretical metrics were also derived.

Results

There were 11 POE and 18 unexposed infants included in the analysis. Pairwise connectivity based on fiber count showed alterations in 32 connections. Pairwise connectivity based on FA values showed alterations in 24 connections. Connections between the right superior frontal gyrus and right paracentral lobule and between the right superior occipital gyrus and right fusiform gyrus were significantly different after adjusting for multiple comparisons between POE infants and unexposed controls. Additionally, alterations in graph theoretical network metrics were identified with fiber count and FA value derived tracts.

Conclusion

Comparisons show significant differences in fiber count in two structural connections. The long-term clinical outcomes related to these findings may be assessed in longitudinal follow-up studies.

Cerebral perfusion and neurological examination characterise neonatal opioid withdrawal syndrome: a prospective cohort study

OBJECTIVE

To test the hypothesis that cerebral blood flow (CBF) assessed with arterial spin labelling (ASL) MRI is increased and standardised neurological examination is altered in infants with neonatal opioid withdrawal syndrome (NOWS) compared with those without.

DESIGN

Prospective cohort study.

SETTING

Level IV neonatal intensive care unit and outpatient primary care centre.

PARTICIPANTS

Infants with NOWS receiving pharmacological treatment and unexposed controls matched for gestational age at birth and post-menstrual age at MRI.

MAIN OUTCOMES

CBF assessed by ASL on non-sedated 3-Tesla MRI and standardised Hammersmith Neonatal Neurological Examination (HNNE) within 14 days of birth.

RESULTS

Thirty infants with NOWS and 31 control infants were enrolled and included in the final analysis. Global CBF across the brain was higher in the NOWS group compared with controls (14.2 mL/100 g/min±5.5 vs 10.7 mL/100 g/min±4.3, mean±SD, Cohen's d=0.72). HNNE total optimality score was lower in the NOWS group compared with controls (25.9±3.6 vs 28.4±2.4, mean±SD, Cohen's d=0.81). A penalised logistic regression model including both CBF and HNNE items discriminated best between the two groups.

CONCLUSIONS

Increased cerebral perfusion and neurological examination abnormalities characterise infants with NOWS compared with those without intrauterine drug exposure and suggest prenatal substance exposure affects fetal brain development. Identifying neurological and neuroimaging characteristics of infants with NOWS can contribute to understanding mechanisms underlying later outcomes and to designing potential new treatments.

Perinatal methadone exposure attenuates myelination and induces oligodendrocyte apoptosis in neonatal rat brain

Methadone (MTD) is a commonly prescribed treatment for opioid use disorder in pregnancy, despite limited information on the effects of passive exposure on fetal brain development. Animal studies suggest a link between perinatal MTD exposure and impaired white matter development. In this study, we characterized the effect of perinatal MTD exposure through the evaluation of oligodendrocyte development and glial cell activation in the neonatal rat brain. Six pregnant Sprague Dawley rat dams were randomized to MTD (0.2 mL/L) or untreated drinking water from embryonic day 7. Pups were terminated at postnatal day 7 and tissue sections were harvested from six randomly selected pups (one male and one female per litter) of each experimental group for immunohistochemistry in areas of corpus callosum (CC), lateral CC, external capsule (EC), and cerebellar white matter. In the MTD-exposed rat pups, myelination was significantly decreased in the CC, lateral CC, EC, and arbor vitae compared with the controls. The increased density and percentage of oligodendrocyte precursor cells (OPCs) were observed in the CC and cerebellar white matter. The highly active proliferation of OPCs as well as decreased density and percentage of differentiated oligodendrocytes were found in the cerebellum but no differences in the cerebrum. Apoptotic activities of both differentiated oligodendrocytes and myelinating oligodendrocytes were significantly increased in all regions of the cerebrum and cerebellum after MTD exposure. There was no quantitative difference in astrocyte, however, cell density and/or morphologic difference consistent with activation were observed in microglia throughout MTD-exposed CC and cerebellum. Taken together, perinatal MTD exposure reveals global attenuation of myelination, accelerated apoptosis of both differentiated and myelinating oligodendrocytes, and microglia activation, supporting an association between antenatal MTD exposure and impaired myelination in the developing brain.

Adverse Prenatal Exposures and Fetal Brain Development: Insights From Advanced Fetal Magnetic Resonance Imaging

Converging evidence from clinical and preclinical studies suggests that fetal vulnerability to adverse prenatal exposures increases the risk for neuropsychiatric diseases such as autism spectrum disorder, schizophrenia, and depression. Recent advances in fetal magnetic resonance imaging have allowed us to characterize typical fetal brain growth trajectories in vivo and to interrogate structural and functional alterations associated with intrauterine exposures, such as maternal stress, environmental toxins, drugs, and obesity. Here, we review proposed mechanisms for how prenatal influences disrupt neurodevelopment, including the role played by maternal and fetal inflammatory responses. We summarize insights from magnetic resonance imaging research in fetuses, highlight recent discoveries in normative fetal development using quantitative magnetic resonance imaging techniques (i.e., three-dimensional volumetry, proton magnetic resonance spectroscopy, placental diffusion imaging, and functional imaging), and discuss how baseline trajectories are shaped by prenatal exposures.

Thalamocortical functional connectivity in infants with prenatal opioid exposure correlates with severity of neonatal opioid withdrawal syndrome

PURPOSE

Prenatal opioid exposure (POE) is a growing public health concern due to its associated adverse outcomes including neonatal opioid withdrawal syndrome (NOWS). The aim of this study was to assess alterations in thalamic functional connectivity in neonates with POE using resting-state functional magnetic resonance imaging (rs-fMRI) and identify whether these altered connectivity measures were associated with NOWS severity.

METHODS

In this prospective, IRB-approved study, we performed rs-fMRI in 19 infants with POE and 20 healthy control infants without POE. Following standard pre-processing, we performed seed-based functional connectivity analysis with the right and left thalamus as the regions of interest. We performed post hoc analysis in the prenatal opioid exposure group to identify associations of altered thalamocortical connectivity with severity of NOWS. P value of < .05 was considered statistically significant.

RESULTS

There were several regions of significantly altered thalamic to cortical functional connectivity in infants with POE compared to the healthy infants. Distinct regions of thalamocortical functional connectivity correlated with maximum modified Finnegan score. Association between thalamocortical connectivity and severity of NOWS was nominally modified by maternal psychological conditions and polysubstance use.

CONCLUSION

Our findings reveal prenatal opioid exposure-related alterations in thalamic functional connectivity in the infant brain that are correlated with severity of NOWS. Future studies may benefit from evaluation of thalamocortical resting state functional connectivity in infants with POE to help  stratify risk of long term neurodevelopmental outcomes.

Pilot study of fetal brain development and morphometry in prenatal opioid exposure and smoking on fetal MRI

PURPOSE

The purpose of this study was to assess for any differences in brain maturation, structure and morphometry in fetuses exposed to opioids in utero, compared to non-opioid exposed fetuses on fetal MRI.

METHODS

We performed a prospective study in pregnant women using opioids and healthy pregnant women without prenatal opioid use. We evaluated brain maturation, structure, and morphometry on second or third trimester fetal MRI and assessed group differences.

RESULTS

28 pregnant women were enrolled, 12 with opioid exposure (average gestational age 33.67, range 28-39 w), 9 of whom also smoked, and 16 without opioid exposure (average gestational age 32.53, range 27-38 w). There was a significant difference in the anteroposterior diameter of the fetal cerebellar vermis in the opioid exposed fetuses compared to non-opioid exposed fetuses (p = 0.004). There were no significant differences in brain biparietal diameter, fronto-occipital diameter, transverse cerebellar diameter and anteroposterior dimension of the pons in opioid exposed fetuses compared to non-opioid exposed fetuses. There were no abnormalities in brain maturation and no major brain structural abnormalities in the opioid exposed fetuses.

CONCLUSION

Smaller fetal anteroposterior cerebellar vermian dimension was associated with in utero opioid exposure. There were no abnormalities in brain maturation or major structural abnormalities in fetuses exposed to opioids.

Global Brain Functional Network Connectivity in Infants With Prenatal Opioid Exposure

BACKGROUND

Infants with prenatal opioid and substance exposure are at higher risk of poor neurobehavioral outcomes in later childhood. Early brain imaging in infancy has the potential to identify early brain developmental alterations that may help predict behavioral outcomes in these children. In this study, using resting-state functional MRI in early infancy, we aim to identify differences in global brain network connectivity in infants with prenatal opioid and substance exposure compared to healthy control infants.

METHODS AND MATERIALS

In this prospective study, we recruited 23 infants with prenatal opioid exposure and 29 healthy opioid naïve infants. All subjects underwent brain resting-state functional MRI before 3 months postmenstrual age. Covariate Assisted Principal (CAP) regression was performed to identify brain networks within which functional connectivity was associated with opioid exposure after adjusting for sex and gestational age. Associations of these significant networks with maternal comorbidities were also evaluated. Additionally, graph network metrics were assessed in these CAP networks.

RESULTS

There were four CAP network components that were significantly different between the opioid exposed and healthy control infants. Two of these four networks were associated with maternal psychological factors. Intra-network graph metrics, namely average flow coefficient, clustering coefficient and transitivity were also significantly different in opioid exposed infants compared to healthy controls.

CONCLUSION

Prenatal opioid exposure is associated with alterations in global brain functional networks compared to non-opioid exposed infants, with intra-network alterations in graph network modeling. These network alterations were also associated with maternal comorbidity, especially mental health. Large-scale longitudinal studies can help in understanding the clinical implications of these early brain functional network alterations in infants with prenatal opioid exposure.

Co-occurrence of preconception maternal childhood adversity and opioid use during pregnancy: Implications for offspring brain development

Understanding of the effects of in utero opioid exposure on neurodevelopment is a priority given the recent dramatic increase in opioid use among pregnant individuals. However, opioid abuse does not occur in isolation-pregnant individuals abusing opioids often have a significant history of adverse experiences in childhood, among other co-occurring factors. Understanding the specific pathways in which these frequently co-occurring factors may interact and cumulatively influence offspring brain development in utero represents a priority for future research in this area. We highlight maternal history of childhood adversity (CA) as one such co-occurring factor that is more prevalent among individuals using opioids during pregnancy and which is increasingly shown to affect offspring neurodevelopment through mechanisms beginning in utero. Despite the high incidence of CA history in pregnant individuals using opioids, we understand very little about the effects of comorbid prenatal opioid exposure and maternal CA history on fetal brain development. Here, we first provide an overview of current knowledge regarding effects of opioid exposure and maternal CA on offspring neurodevelopment that may occur during gestation. We then outline potential mechanistic pathways through which these factors might have interactive and cumulative influences on offspring neurodevelopment as a foundation for future research in this area.

Consequences of Parental Opioid Exposure on Neurophysiology, Behavior, and Health in the Next Generations

Substance abuse and the ongoing opioid epidemic represents a large societal burden. This review will consider the long-term impact of opioid exposure on future generations. Prenatal, perinatal, and preconception exposure are reviewed with discussion of both maternal and paternal influences. Opioid exposure can have long-lasting effects on reproductive function, gametogenesis, and germline epigenetic programming, which can influence embryogenesis and alter the developmental trajectory of progeny. The potential mechanisms by which preconception maternal and paternal opioid exposure produce deleterious consequences on the health, behavior, and physiology of offspring that have been identified by clinical and animal studies will be discussed. The timing, nature, dosing, and duration of prenatal opioid exposure combined with other important environmental considerations influence the extent to which these manipulations affect parents and their progeny. Epigenetic inheritance refers to the transmission of environmental insults across generations via mechanisms independent of the DNA sequence. This topic will be further explored in the context of prenatal, perinatal, and preconception opioid exposure for both the maternal and paternal lineage.

Prenatal methadone exposure and child developmental outcomes in 2-year-old children

AIM

To examine the developmental outcomes of children born to opioid-dependent females enrolled in methadone maintenance and identify pre- and postnatal factors that place these children at developmental risk.

METHOD

Ninety-nine methadone-maintained females and their 100 infants (42 females, 58 males, mean gestational age 38.8wks) were recruited during pregnancy/at birth and studied to age 2 years alongside a regionally representative comparison group of 108 non-methadone-maintained females and their 110 infants (62 females, 48 males, mean gestational age 39.2wks). Information about perinatal exposure was collected from medical records, maternal urine and infant meconium toxicological analysis, maternal interviews (at birth and at 18mo), and a home visit (at 18mo). At age 2 years, child neuromotor function, cognition, language, and emotional/behavioral dysregulation were assessed.

RESULTS

Opioid-exposed children achieved lower motor, cognitive, and language scores and had poorer self, emotional, eating/feeding, and sensory processing regulation than unexposed children. After adjustment for maternal education and other substance use in pregnancy, between-group differences in child motor, cognitive, and overall dysregulation remained. Postnatal parental and family factors explained a further 40% to 52% of between-group differences in child outcomes.

INTERPRETATION

These children and families are extremely high-risk and need antenatal and postnatal support. Children exposed to opioids during pregnancy have pervasive developmental difficulties by age 2 years. These challenges are largely explained by adverse pregnancy and socio-environmental exposures, emphasizing the importance of specialist prenatal care and postnatal intervention support. What this paper adds Children born to opioid-dependent females are at high risk of pervasive developmental problems. These problems span a range of functional domains, including motor, cognitive, language, and behavioral/emotional dysregulation. Contributing factors include other adverse pregnancy exposures, postnatal environmental factors, and the direct effects of prenatal opioid exposure.

Prenatal methadone exposure impairs adolescent cognition and GABAergic neurodevelopment in a novel rat model of maternal methadone treatment

Methadone maintenance treatment (MMT) is the most common treatment for opioid-dependent pregnant women worldwide. Despite its widespread use, MMT is associated with a variety of adverse neurodevelopmental outcomes in exposed offspring, particularly cognitive impairments. The neurobiological abnormalities underlying these cognitive impairments are, however, poorly understood. This is, in part, due to a lack of animal models that represents the standard of care that methadone is administered in the clinic, with inconsistencies in the timing, doses and durations of treatment. Here we describe the characterisation of a clinically relevant rat model of MMT in which the long-term behavioural and neurobiological effects of prenatal methadone exposure can be assessed in adolescent offspring. Female Sprague-Dawley rats were treated orally with an ascending methadone dosage schedule (5, 10, 15, 20, 25 and 30 mg/kg/day), self-administered in drinking water prior to conception, throughout gestation and lactation. Pregnancy success, maternal gestational weight gain, litter survival and size were not significantly altered in methadone-exposed animals. Methadone-exposed offspring body and brain weights were significantly lower at birth. Novel object recognition tests performed at adolescence revealed methadone-exposed offspring had impaired recognition memory. Furthermore, the rewarded T-maze alternation task demonstrated that methadone-exposed female, but not male, offspring also exhibit working memory and learning deficits. Immunoblots of the adolescent prefrontal cortex and hippocampus showed methadone-exposed offspring displayed reduced levels of mature BDNF, in addition to the GABAergic proteins, GAD67 and parvalbumin, in a sex- and brain region-specific fashion. This rat model closely emulates the clinical scenario in which methadone is administered to opioid-dependent pregnant woman and provides evidence MMT can cause cognitive impairments in adolescent offspring that may be underlined by perturbed neurodevelopment of the GABAergic system.

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.

Maternal opioid use disorder: Placental transcriptome analysis for neonatal opioid withdrawal syndrome

Excessive prenatal opioid exposure may lead to the development of Neonatal Opioid Withdrawal Syndrome (NOWS). RNA-seq was done on 64 formalin-fixed paraffin-embedded placental tissue samples from 32 mothers with opioid use disorder, with newborns with NOWS that required treatment, and 32 prenatally unexposed controls. We identified 93 differentially expressed genes in the placentas of infants with NOWS compared to unexposed controls. There were 4 up- and 89 downregulated genes. Among these, 7 genes CYP1A1, APOB, RPH3A, NRXN1, LINC01206, AL157396.1, UNC80 achieved an FDR p-value of <0.01. The remaining 87 genes were significant with FDR p-value <0.05. The 4 upregulated, CYP1A1, FP671120.3, RAD1, RN7SL856P, and the 10 most significantly downregulated genes were RNA5SP364, GRIN2A, UNC5D, DMBT1P1, MIR3976HG, LINC02199, LINC02822, PANTR1, AC012178.1, CTNNA2. Ingenuity Pathway Analysis identified the 7 most likely to play an important role in the etiology of NOWS. Our study expands insights into the genetic mechanisms of NOWS development.

Prenatal opioid exposure is associated with smaller brain volumes in multiple regions

BACKGROUND

The impact of prenatal opioid exposure on brain development remains poorly understood.

METHODS

We conducted a prospective study of term-born infants with and without prenatal opioid exposure. Structural brain MRI was performed between 40 and 48 weeks postmenstrual age. T2-weighted images were processed using the Developing Human Connectome Project structural pipeline. We compared 63 relative regional brain volumes between groups.

RESULTS

Twenty-nine infants with prenatal opioid exposure and 42 unexposed controls were included. The groups had similar demographics, except exposed infants had lower birth weights, more maternal smoking and maternal Hepatitis C, fewer mothers with a college degree, and were more likely non-Hispanic White. After controlling for sex, postmenstrual age at scan, birth weight, and maternal education, exposed infants had significantly smaller relative volumes of the deep gray matter, bilateral thalamic ventrolateral nuclei, bilateral insular white matter, bilateral subthalamic nuclei, brainstem, and cerebrospinal fluid. Exposed infants had larger relative volumes of the right cingulate gyrus white matter and left occipital lobe white matter.

CONCLUSIONS

Infants with prenatal opioid exposure had smaller brain volumes in multiple regions compared to controls, with two regions larger in the opioid-exposed group. Further research should focus on the relative contributions of maternal opioids and other exposures.

IMPACT

Prenatal opioid exposure is associated with developmental and behavioral consequences, but the direct effects of opioids on the developing human brain are poorly understood. Prior small studies using MRI have shown smaller regional brain volumes in opioid-exposed infants and children. After controlling for covariates, infants with prenatal opioid exposure scanned at 40-48 weeks postmenstrual age had smaller brain volumes in multiple regions compared to controls, with two regions larger in the opioid-exposed group. This adds to the literature showing potential impact of prenatal opioid exposure on the developing brain.

Neuroimaging in infants with prenatal opioid exposure: Current evidence, recent developments and targets for future research

Prenatal opioid exposure (POE) has shown to be a risk factor for adverse long-term cognitive and behavioral outcomes in offspring. However, the neural mechanisms of these outcomes remain poorly understood. While preclinical and human studies suggest that these outcomes may be due to opioid-mediated changes in the fetal and early postnatal brain, other maternal, social, and environmental factors are also shown to play a role. Recent neuroimaging studies reveal brain alterations in children with POE. Early neuroimaging and novel methodology could provide an in vivo mechanistic understanding of opioid mediated alterations in developing brain. However, this is an area of ongoing research. In this review we explore recent imaging developments in POE, with emphasis on the neonatal and infant brain, and highlight some of the challenges of imaging the developing brain in this population. We also highlight evidence from animal models and imaging in older children and youth to understand areas where future research may be targeted in infants with POE.

Neonatal Opioid Withdrawal Syndrome (NOWS): A Transgenerational Echo of the Opioid Crisis

The incidence of neonatal opioid withdrawal syndrome (NOWS) has increased substantially in the setting of the opioid epidemic, a major public health problem in the United States. At present, NOWS has commonly used assessment and treatment protocols, but new protocols have questioned old practices. However, because of limited access to opioid use disorder (OUD) treatment and socioeconomic factors, many pregnant (and postpartum) women with OUD do not receive treatment. The pathophysiology of NOWS is not completely understood, although limited research studies have been conducted in humans and animals to better understand its etiology. Moreover, there is evidence that epigenetic and genetic factors play a role in the development of NOWS, but further study is needed. Animal models have suggested that there are deleterious effects of in utero opioid exposure later in life. Clinical research has revealed the harmful long-term sequelae of NOWS, with respect to cognitive function and childhood development. Many psychiatric disorders begin during adolescence, so as infants born with NOWS approach adolescence, additional clinical and molecular studies are warranted to identify biologic and psychosocial risk factors and long-term effects of NOWS. Additionally, access to specialized OUD treatment for pregnant women must be more readily available in the United States, especially in rural areas.

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.

Prenatal opioid exposure - Increasing evidence of harm

Prenatal opioid exposure adversely impacts upon fetal growth and places the newborn at risk of neonatal opioid withdrawal. The severity and duration of opioid withdrawal cannot be predicted in the individual baby and may be contributed to by other drugs including benzodiazepines and alcohol as well as cigarette smoking. Mitigating factors include breastfeeding, rooming in and absence of maternal polypharmacy. Less well recognised are a variety of other complications associated with prenatal opioid exposure including epigenetic changes, effects on neurophysiological function and structural alterations to the developing brain. The visual system is significantly affected, with changes to both clinical and electrophysiological function persisting at least to mid-childhood. Longer term neurodevelopmental and behavioural outcomes are confounded by multiple factors including poverty, parent-child interaction and small study numbers, but systematic reviews consistently demonstrate poorer outcomes for those children and young people prenatally exposed to opioids. Crucially, manifestation of neonatal withdrawal is not a prerequisite for important long term problems including behavioural, emotional or motor function disorder, sensory or speech disorder, strabismus and nystagmus. A body of evidence supports an independent adverse effect of prenatal opioid exposure upon fetal brain development, mediated via a systemic neuro-inflammatory process. Children prenatally exposed to opioids should remain under appropriate follow up, at least until school entry, as difficulties may only become apparent in mid-childhood. Future studies of the management of opioid use disorder in pregnancy, including maintenance methadone, must include longer term outcomes for the baby.

Resting state functional MRI in infants with prenatal opioid exposure-a pilot study

PURPOSE

Exposure to prenatal opioids may adversely impact the developing brain networks. The aim of this pilot study was to evaluate alterations in amygdalar functional connectivity in human infants with prenatal opioid exposure.

METHODS

In this prospective IRB approved study, we performed resting state functional MRI (rs-fMRI) in 10 infants with prenatal opioid exposure and 12 infants without prenatal drug exposure at < 48 weeks corrected gestational age. Following standard preprocessing, we performed seed-based functional connectivity analysis with the right and left amygdala as the regions of interest after correcting for maternal depression and infant sex. We compared functional connectivity of the amygdala network between infants with and without prenatal opioid exposure.

RESULTS

There were significant differences in connectivity of the amygdala seed regions to the several cortical regions including the medial prefrontal cortex in infants who had prenatal opioid exposure when compared with opioid naïve infants.

CONCLUSION

This finding of increased amygdala functional connectivity in infants with in utero opioid exposure suggests a potential role of maternal opioid exposure on infants' altered amygdala function. This association with prenatal exposure needs to be replicated in future larger studies.

Prenatal exposure to methadone or buprenorphine alters µ-opioid receptor binding and downstream signaling in the rat brain

There is a growing concern related to the use of opioid maintenance treatment during pregnancy. Studies in both humans and animals have reported reduced cognitive functioning in offspring prenatally exposed to methadone or buprenorphine; however, little is known about the neurobiological mechanisms underlying these impairments. To reveal possible neurobiological effects of such in utero exposure, we examined brain tissue from methadone- and buprenorphine-exposed rat offspring previously shown to display impaired learning and memory. We studied µ-opioid receptor (MOR) and N-methyl-D-aspartate receptor (NMDAR) binding in the rat offspring cerebrum during development and in the hippocampus at young adulthood. Moreover, we examined activation of the Ca2+ /calmodulin-dependent protein kinase II (CaMKII) and the extracellular signal-regulated kinase (ERK), which are central in the downstream signaling of these receptors. The methadone- and buprenorphine-exposed rat pups displayed reduced MOR binding up to two weeks after birth, whereas the NMDAR binding was unaffected. Prenatal exposure to methadone or buprenorphine also resulted in decreased activation of CaMKII and/or ERK during development, while young adult offspring displayed increased hippocampal ERK activation. In conclusion, our findings suggest that prenatal exposure to exogenous opioids, such as methadone or buprenorphine, may disturb the endogenous opioid system during development, with long-term effects on proteins important for cognitive functioning.

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.

Neurodevelopmental Outcomes of Children Born to Opioid-Dependent Mothers: A Systematic Review and Meta-Analysis

BACKGROUND

Children born to opioid-dependent mothers are at risk of adverse neurodevelopment. The magnitude of this risk remains inconclusive.

OBJECTIVE

To conduct a meta-analysis of studies that assessed neurodevelopmental outcomes of children aged 0 to 12 years born to opioid-dependent mothers, compared with children born to nonopioid-dependent mothers, across general cognitive, language, motor, and social-emotional domains.

DATA SOURCES

PubMed, CINAHL, PsycINFO, and Google Scholar databases.

STUDY ELIGIBILITY CRITERIA

English-language publications between January 1993 and November 2018, including prenatally opioid-exposed and nonopioid-exposed comparison children, reporting outcomes data on standardized assessments.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers independently extracted data. Pooled standardized mean differences (SMDs) were analyzed using random effects models. Risk of bias was assessed with the Newcastle-Ottawa Quality Assessment Scale.

RESULTS

Across 16 studies, individual domain outcomes data were examined for between 93 to 430 opioid-exposed and 75 to 505 nonopioid-exposed infants/children. Opioid-exposed infants and children performed more poorly than their nonopioid-exposed peers across all outcomes examined, demonstrated by lower infant cognitive (SMD = 0.77) and psychomotor scores (SMD = 0.52), lower general cognition/IQ (SMD = 0.76) and language scores (SMD = 0.65-0.74), and higher parent-rated internalizing (SMD = 0.42), externalizing (SMD = 0.66), and attention problems (SMD = 0.72).

LIMITATIONS

Most studies examined early neurodevelopment; only 3 reported school-age outcomes thereby limiting the ability to assess longer-term impacts of prenatal opioid exposures.

CONCLUSIONS AND IMPLICATIONS OF FINDINGS

Children born to opioid-dependent mothers are at modest- to high-risk of adverse neurodevelopment at least to middle childhood. Future studies should identify specific clinical and social factors underlying these challenges to improve outcomes.

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.

Opioids affect the fetal brain: reframing the detoxification debate

Medication-assisted treatment is recommended for individuals with an opioid use disorder, including pregnant women. Medication-assisted treatment during pregnancy provides benefits to the mother and fetus, including better pregnancy outcomes, reduced illicit drug use, and improved prenatal care. An alternative approach, medically supervised withdrawal (detoxification), has, in recent reports, demonstrated a low risk of fetal death and low rates of relapse and neonatal abstinence syndrome. The rates of relapse and neonatal abstinence syndrome are questioned by many who view medically supervised withdrawal as unacceptable based on the concern for the potential adverse consequences of relapse to mother and baby. The impact of opioids on the fetal brain have not been integrated into this debate. Studies in animals and human brain tissues demonstrate opioid receptors in neurons, astroglia, and oligodendrocytes. Age-specific normative data from infants, children, and adults have facilitated investigation of the impact of opioids on the human brain in vivo. Collectively, these studies in animals, human neural tissue, adult brains, and the brains of children and newborns demonstrate that opioids adversely affect the human brain, primarily the developing oligodendrocyte and the processes of myelinization (white matter microstructure), connectivity between parts of the brain, and the size of multiple brain regions, including the basal ganglia, thalamus, and cerebellar white matter. These in vivo studies across the human lifespan suggest vulnerability of specific fronto-temporal-limbic and frontal-subcortical (basal ganglia and cerebellum) pathways that are also likely vulnerable in the human fetal brain. The long-term impact of these reproducible changes in the fetal brain in vivo is unclear, but the possibility of lasting injury has been suggested. In light of the recent data on medically supervised withdrawal and the emerging evidence suggesting adverse effects of opioids on the developing fetal brain, a new paradigm of care is needed that includes the preferred option of medication-assisted treatment but also the option of medically supervised opioid withdrawal for a select group of women. Both these treatment options should offer mental health and social services support throughout pregnancy. More research on both opioid exposure on the developing human brain and the impact of medically supervised withdrawal is required to identify appropriate candidates, optimal dose reduction regimens, and gestational age timing for initiating medically supervised withdrawal.

White Matter Injury and Structural Anomalies in Infants with Prenatal Opioid Exposure

Previous studies have not found structural injury or brain malformations in infants and children with prenatal opioid exposure. As part of an ongoing study evaluating neuroimaging in infants with prenatal opioid exposure, we reviewed structural brain MR imaging in 20 term infants with prenatal opioid exposure and 20 term controls at 4-8 weeks of age. We found that 8 of the 20 opioid-exposed infants had punctate white matter lesions or white matter signal abnormality on structural MR imaging, and 2 of the opioid-exposed infants had a septopreoptic fusion anomaly. No controls had white matter injury or structural malformations. Our findings underscore the importance of clinical neurodevelopmental follow-up and the need for more comprehensive imaging and long-term outcomes research following prenatal opioid exposure.

Persistent feeding difficulties among infants with fetal opioid exposure: mechanisms and clinical reasoning

Aims: Infants with fetal exposure to opioids have varying pattern of feeding difficulties mainly manifesting as difficulties with aerodigestive adaptation and disruptive feeding behavior. The reasons are unclear; in a pilot study, we determined basal and adaptive pharyngo-esophageal motility in a group of infants with fetal exposure to opioids and persistent feeding difficulties impeding their discharge. Methods: Six infants with fetal opioid exposure compared to 12 controls who underwent basal and adaptive pharyngo-esophageal manometry to characterize the basis for their symptoms. Spontaneous swallows (N = 180) and pharyngeal stimuli (N = 113)-induced swallowing responses were analyzed. Results: Resting upper esophageal sphincter (UES) pressure was similar in both the groups, but resting lower esophageal sphincter (LES) pressure was significantly high and it relaxed slowly and inadequately in opioid-exposed infants (p < .05). Upon pharyngeal provocation, opioid-exposed infants had higher LES nadir pressure, increased duration of esophageal body contraction at proximal-, mid-, and distal-esophagus, as well as greater area under the curve with distal esophageal waveforms, compared to controls (all p < .05). Conclusions: These pilot observations are suggestive of up-regulation of central vagal effects with heightened cholinergic excitatory responses and inadequate relaxation responses at the foregut, and may form the basis for persistent feeding difficulties in opioid-exposed infants. Abnormality with both sensory and motor aspects of vagal reflexes may be contributory.

Educational achievement at age 9.5 years of children born to mothers maintained on methadone during pregnancy

Recent research shows that preschool children born to opioid-dependent mothers are at increased risk for cognitive, psychomotor, attention, and social-emotional adjustment problems. But very little is known about their school-age functioning, particularly their educational achievement. This analysis examined the educational outcomes of a regional cohort of 100 prenatally methadone-exposed children who were prospectively studied from birth to age 9.5 years alongside a comparison group of 110 randomly identified non-exposed children born between 2003 and 2008. At age 9.5, as part of a comprehensive neurodevelopmental evaluation, children's teachers rated their achievement across the school curriculum, and children completed the Woodcock Johnson-III Tests of Achievement (WJ-III). Detailed information about the birth mother's social background, pregnancy substance use, and mental health was also collected during pregnancy/at term. Infant clinical data were collected after birth. Methadone-exposed children performed less well than non-exposed children across seven school curriculum areas rated by teachers (ps ≤.001), performed less well than non-exposed children on all reading and mathematics subtests of the WJ-III, and had higher rates of any educational delay on the WJ-III (57% vs. 15%), OR = 7.47 (3.71-15.02). Results were similar when children with severe intellectual impairment were excluded. After adjusting for confounding factors, methadone-exposed children had increased odds of educational delay, but this was only marginally significant (OR = 3.62, [1.01-13.01], p = .049). Maternal educational attainment level (OR = 0.69, [0.50-0.89], p = .006), and maternal benzodiazepine use during pregnancy (OR = 2.70 [1.03-7.12], p = .044) were also associated with later educational risk. Findings suggest that children born to opioid-dependent women enrolled in methadone maintenance are at high risk of educational delay by age 9.5 years. Children's academic difficulties appeared to reflect the effects of both adverse prenatal exposures and postnatal social risk.

After NAS

Mothers have used opioids for thousands of years but neonatal abstinence syndrome (NAS) or rather, survivors of NAS, is a modern phenomenon. Unrecognized and/or untreated opioid withdrawal was almost always fatal but with greater awareness and standardization of treatment, NAS is now an uncommon direct cause of infant death. However, opioids are now increasingly accessible and potent and the outcomes of children after the neonatal period are of great concern, especially when coupled with multiple other social and health risks. Complex individual, environmental and genetic factors need to be considered when assessing outcomes or future research for babies with NAS. Any intervention or research efforts must address these multifactorial complexities. This review will discuss pertinent post neonatal outcomes, including mortality, physical and mental health and social functioning of children with a history of NAS.