Maternal vagal tone change in response to methadone is associated with neonatal abstinence syndrome severity in exposed neonates

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.

Maternal psychophysiology profiles: associations with prenatal opioid use, maternal emotion dysregulation, and newborn neurobehavior

BACKGROUND

Opioid use among pregnant women has more than quadrupled over the past 20 years; however, comorbid risk factors such as emotion dysregulation confound the developmental consequences of prenatal opioid use. Maternal respiratory sinus arrhythmia (RSA) may help to disentangle the comorbid risk factors of prenatal emotion dysregulation and substance use and isolate their consequences on newborn neurobehavior.

METHODS

We examined maternal RSA in response to a mild, infant-related stress task in pregnant people (N = 192; 30 on medications for opioid use disorder) recruited from hospitals and a specialty prenatal clinic for substance use disorder.

RESULTS

Three latent profiles emerged based on maternal RSA reactivity. Mothers with RSA increasing (Profile 3; more nervous system dysregulation) had higher levels of emotion dysregulation than mothers with RSA decreasing (Profile 1; well-regulated nervous system responses) but were not more likely to use opioids. Additionally, RSA profiles were associated with newborn neurobehavior, including attention, regulation, handling, and arousal.

CONCLUSIONS

Given the variability in opioid use across RSA profiles and profile associations with newborn neurodevelopment, future studies should examine protective factors in pregnant individuals using opioids who show more flexible RSA responses.

IMPACT

Our study examined maternal psychophysiology and newborn outcomes in a unique population with high levels of emotion dysregulation and opioid use. Three profiles of maternal respiratory sinus arrythmia (RSA) reactivity were identified during pregnancy: decreasing, blunted, and increasing. The RSA increasing and blunted profiles were associated with higher emotion dysregulation than the decreasing profile. Most pregnant people on medications for opioid use disorder (65%) were grouped into the blunted profile, suggesting they might be more at risk for dysregulated RSA reactivity. Differences in RSA profiles were associated with newborn outcomes, with increasing and blunted RSA predicting more newborn neurobehavioral dysregulation.

Gestational PBDE concentrations, persistent externalizing, and emerging internalizing behaviors in adolescents: The HOME study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental chemicals used as flame retardants in commercial and consumer products. Gestational PBDE concentrations are associated with adverse behaviors in children; however, the persistence of these associations into adolescence remains understudied.

OBJECTIVE

We estimated the association of gestational PBDE serum concentrations with early adolescent self- and caregiver-reported behaviors at age 12 years and determined the consistency with previously observed associations in childhood with caregiver-reported behaviors in a prospective pregnancy and birth cohort.

METHODS

We measured maternal serum concentrations of five individual PBDE congeners and created a summary exposure variable (∑5BDE: 28, -47, -99, -100 and -153) during pregnancy. At age 12 years, we assessed behaviors for 237 adolescents using self- and caregiver-reports with the Behavioral Assessment System for Children-3 (BASC3). We used multivariable linear regression models to estimate covariate-adjusted associations of lipid standardized, log10-transformed gestational PBDE concentrations with BASC3 scores. We obtained estimates and 95% confidence intervals through a bootstrapping approach. We evaluated potential effect measure modification (EMM) of adolescent sex by examining sex-stratified regression models and estimating the EMM p-values.

RESULTS

Gestational PBDE concentrations were positively associated with adolescent-reported BASC3 composite indices for inattention & hyperactivity (BDE-28, -47, -99, -100, ∑5BDE), internalizing problems (BDE-28, -47, -99), functional impairment (BDE-28, ∑5BDE), and emotional symptoms (BDE-28). Gestational PBDE concentrations were positively associated with caregiver-reported BASC3 composite indices for externalizing problems (BDE-28, -47, -99, -100, -153, ∑5BDE) and behavioral symptoms (BDE-99). For caregiver reported behaviors, we observed stronger associations with gestational BDE concentrations among males, especially for executive functioning (BDE-28, -47, -99, -100, ∑5BDE).

DISCUSSION

Gestational PBDE serum concentrations were associated with self-reported internalizing and externalizing behavior problems in early adolescence. Caregiver-reported externalizing behaviors recognized during childhood remain associated with gestational PBDE concentrations and persist into early adolescence. Internalizing behaviors were less recognized by caregivers.

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.

Effects of prenatal opioid exposure on infant sympathetic and parasympathetic nervous system activity

Prenatal opioid exposure has been associated with developmental problems, including autonomic nervous system dysregulation. However, little is known about the effects of prenatal opioid exposure on the autonomic nervous system beyond the first days of life, particularly across both the parasympathetic and sympathetic branches, and when accounting for exposure to other substances. The present study examined the effects of prenatal exposure to opioid agonist therapy (OAT, e.g., methadone) and other opioids on infant autonomic nervous system activity at rest and in response to a social stressor (the Still-Face Paradigm) at six months among 86 infants varying in prenatal opioid and other substance exposure. Results indicated that OAT and other opioids have unique effects on the developing autonomic nervous system that may further depend on subtype (i.e., methadone versus buprenorphine) and timing in gestation. Results are discussed in the context of theoretical models of the developing stress response system.

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.

Maternal Substance Use and Early-Life Adversity: Inducing Drug Dependence in Offspring, Interactions, Mechanisms, and Treatments

The likelihood of substance dependency in offspring is increased in cases when there is a family history of drug or alcohol use. Mothering is limited by maternal addiction because of the separation. Maternal separation (MS) leads to the development of behavioural and neuropsychiatric issues in the future. Despite the importance of this issue, empirical investigations of the influences of maternal substance use and separation on substance use problems in offspring are limited, and studies that consider both effects are rare. This study aims to review a few studies on the mechanisms, treatments, genetics, epigenetics, molecular and psychological alterations, and neuroanatomical regions involved in the dependence of offspring who underwent maternal addiction and separation. The PubMed database was used. A total of 95 articles were found, including the most related ones in the review. The brain's lateral paragigantocellularis (LPGi), nucleus accumbens (NAc), caudate-putamen (CPu), prefrontal cortex (PFC), and hippocampus, can be affected by MS. Dopamine receptor subtype genes, alcohol biomarker minor allele, and preproenkephalin mRNA may be affected by alcohol or substance use disorders. After early-life adversity, histone acetylation in the hippocampus may be linked to brain-derived neurotrophic factor (BDNF) gene epigenetics and glucocorticoid receptors (GRs). The adverse early-life experiences differ in offspring›s genders and rewire the brain›s dopamine and endocannabinoid circuits, making offspring more susceptible to dependence. Related psychological factors rooted in early-life stress (ELS) and parental substance use disorder (SUD). Treatments include antidepressants, histone deacetylase inhibitors, lamotrigine, ketamine, choline, modafinil, methadone, dopamine, cannabinoid 1 receptor agonists/antagonists, vitamins, oxytocin, tetrahydrocannabinol, SR141716A, and dronabinol. Finally, the study emphasizes the need for multifaceted strategies to prevent these outcomes.

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'.

Neonatal Outcomes after Combined Opioid and Nicotine Exposure in Utero: A Scoping Review

BACKGROUND

The majority of women who are pregnant with opioid use disorder (OUD) also smoke tobacco but are rarely offered tobacco cessation counseling. While the effects of exposure to opioids and nicotine in utero are well-understood separately, understanding the impact of the combined exposure to these substances on neonatal outcomes is lacking.

METHODS

A scoping review was conducted using PubMed and Scopus databases for studies addressing the combined exposure to opioids and nicotine during pregnancy published between 1 January 1980 and 9 July 2019. A total of 29 papers met the eligibility criteria for inclusion, with nine being identified as clinical trials (three from the MOTHER study) and two as secondary data analysis of clinical trial data.

RESULTS

Neonatal outcomes for infants who had a combined exposure to opioids and nicotine in utero indicated a reduction in birth weight and birth length. Findings in infants exposed to both nicotine and opioids were mixed with regard to the duration of neonatal abstinence syndrome (NAS), the likelihood of treatment for NAS, doses of medicine used to treat NAS, and NAS scores when compared with infants who had opioid exposure without nicotine.

CONCLUSIONS

The combined exposure to nicotine and opioids during pregnancy may lead to a reduction in neonatal birth weight and birth length and more severe NAS signs, compared with opioid use alone, but more research is necessary to identify the minimum dosage and length of nicotine exposure to accurately predict these outcomes.

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.

Gender Differences in the Outcome of Offspring Prenatally Exposed to Drugs of Abuse

Despite great efforts to warn pregnant women that drugs of abuse impact development of the embryo and the fetus, the use of legal and illegal drugs by childbearing women is still a major public health concern. In parallel with well-established teratogenic effects elicited by some drugs of abuse, epidemiological studies show that certain psychoactive substances do not induce birth defects but lead to subtle neurobehavioral alterations in the offspring that manifest as early as during infancy. Although gender differences in offspring susceptibility have not been fully investigated, a number of longitudinal studies indicate that male and female progeny exposed in utero to drugs of abuse show different vulnerabilities to deleterious effects of these substances in cognitive, executive, and behavioral domains. Here, we briefly review the existing literature focusing on gender differences in the neurobehavioral consequences of maternal exposure to drugs of abuse. Overall, the data strongly indicate that male exposed progeny are more susceptible than female to dysfunctions in cognitive processing and emotional regulation. However, insights into the mechanisms determining this natural phenomenon are not currently available. Our analysis prompts future investigations to implement clinical studies including the influence of gender/sex as a biological variable in the outcome of offspring prenatally exposed to drugs of abuse.

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.

Maternal buprenorphine treatment during pregnancy and maternal physiology

BACKGROUND

Buprenorphine, used for opioid use disorder (OUD) treatment during pregnancy, provides unknown effects on maternal physiological activity. The primary aim of this report is to document acute effects of buprenorphine administration on indicators of maternal autonomic functioning. Effects of maternal buprenorphine dose and other substance exposures on maternal measures were examined, as were neonatal abstinence syndrome (NAS) outcomes.

METHODS

Forty-nine pregnant, buprenorphine-maintained women yielded maternal physiologic information (heart rate and variability, electrodermal activity, and respiratory rate) at 24, 28, 32 and 36 weeks gestation. Monitoring at trough and peak maternal medication levels was implemented to ascertain acute physiologic effects of buprenorphine administration.

RESULTS

Buprenorphine administration accelerated maternal heart rate and reduced variability at two gestational ages (24 and 36 weeks) and suppressed sympathetic (electrodermal) activation at 24, 28 and 32 weeks at times of peak maternal medication levels. Maternal autonomic parameters were unrelated to polysubstance exposure with the exception of cigarette smoking. Heavier smoking dampened maternal heart rate variability across gestation and potentiated reactivity to buprenorphine at 24 and 36 weeks. Heavier smoking was also associated with reduced electrodermal activity at 36 weeks. Buprenorphine dose was unrelated to observed effects. Larger degree of maternal heart rate reactivity to buprenorphine administration was related to more severe NAS expression.

CONCLUSIONS

These findings detail the maternal autonomic response to buprenorphine administration but also illustrate the significant effect of concurrent cigarette use on maternal autonomic regulation. This suggests the importance of smoking-reduction strategies in the comprehensive, medication-assisted treatment of women with OUD.

In Utero Exposure to Norbuprenorphine, a Major Metabolite of Buprenorphine, Induces Fetal Opioid Dependence and Leads to Neonatal Opioid Withdrawal Syndrome

Buprenorphine is the preferred treatment of opioid use disorder during pregnancy but can cause fetal opioid dependence and neonatal opioid withdrawal syndrome (NOWS). Notably, withdrawal severity is independent of maternal buprenorphine dose, suggesting that interindividual variance in pharmacokinetics may influence risk and severity of NOWS. Using a rat model of NOWS, we tested the hypothesis that clinically relevant doses of the active metabolite norbuprenorphine (NorBUP) can induce in utero opioid dependence, manifested as naltrexone-precipitated withdrawal signs in the neonate. Pregnant Long-Evans rats were implanted with 14-day osmotic minipumps containing vehicle, morphine (positive control), or NorBUP (0.3-10 mg/kg per day) on gestation day 9. By 12 hours post-delivery, an intraperitoneal injection of the opioid antagonist naltrexone (1 or 10 mg/kg) or saline was administered to pups. Precipitated withdrawal signs were graded by raters blinded to treatment conditions. In a separate group, NorBUP concentrations in maternal and fetal blood and brain on gestation day 20 were determined by liquid chromatography-tandem mass spectrometry. Steady-state maternal blood concentrations of NorBUP in dams infused with 1 or 3 mg/kg per day were comparable to values reported in pregnant humans treated with buprenorphine (1.0 and 9.6 ng/ml, respectively), suggesting a clinically relevant dosing regimen. At these doses, NorBUP increased withdrawal severity in the neonate as shown by an evaluation of 10 withdrawal indicators. These findings support the possibility that NorBUP contributes to fetal opioid dependence and NOWS following maternal buprenorphine treatment during pregnancy.

Models of care for neonatal abstinence syndrome: What works?

Opioid use disorders and the prescription of long-acting medications for their treatment have increased dramatically over the last decade among pregnant women. Newborns who experience prolonged in utero opioid exposure may develop neonatal abstinence syndrome (NAS). Until recently, much of the focus on improving care for NAS has been on pharmacologically-based care models. Recent studies have illustrated the benefits of rooming-in and parental presence on NAS outcomes. Single center Quality Improvement (QI) initiatives demonstrate the benefits of non-pharmacologic care bundles and symptom prioritization in decreasing the proportion of infants pharmacologically treated and length of hospital stay. Little remains known about the impact of these varied cared models on maternal-infant attachment and mental health. In this review article, we will propose an optimal model of care to improve short- and long-term outcomes for newborns, their mothers and families, and perinatal care systems.

Neonatal Abstinence Syndrome

This review examines the continuum of care of opioid-exposed infants, including the assessment of the neonate, diagnosis of neonatal abstinence syndrome, management of the syndrome including nonpharmacologic and pharmacologic care, approach to breastfeeding, pediatric follow-up care, and integration of care of the mother-infant dyad.

Beyond the Finnegan scoring system: Novel assessment and diagnostic techniques for the opioid-exposed infant

Infants with in-utero opioid exposure are most commonly assessed using the Finnegan Neonatal Abstinence Scoring System (FNASS) or a modified version of that tool. Traditionally, the purpose of these tools has been to characterize the extent of withdrawal signs to guide the pharmacologic treatment for infants with neonatal opioid withdrawal syndrome (NOWS). In the past decade however, in response to some of the limitations of the FNASS tool, there has been an increasing emphasis on developing novel assessment tools not based on the FNASS in addition to the promotion of non-pharmacologic treatment options as the first line treatment for infants with opioid exposure. Additionally, several prediction tools that may be useful in determining which patients are at high or low risk for receiving pharmacologic therapy have been developed. In this review, we will evaluate the clinical utility of these novel tools and will consider new avenues for future research.

Early life stress and environmental influences on the neurodevelopment of children with prenatal opioid exposure

Prenatal opioid exposure has reached epidemic proportions. In the last 10 years, there has been a 242% increase in the number of babies born with the drug withdrawal syndrome known as Neonatal Opioid Withdrawal Syndrome (NOWS). Developmental outcome studies of infants with prenatal opioid exposure are limited by methodological issues including small sample sizes and lack of control for confounding variables such as exposure to poverty and maternal psychopathology. Thus, there is a critical gap in the literature that limits our ability to predict short-term effects of opioid exposure. Here we review direct neurotoxic, indirect, and stress-related pathophysiologies of prenatal opioid exposure. We describe the literature on short and long-term neurodevelopmental outcomes of children with prenatal opioid exposure, highlighting sex differences and the role of early life stress. We conclude by prioritizing avenues for future research for this group of underserved women and their children at risk for neurodevelopmental delays.

Ethical Considerations for Perinatal Toxicology Screening

Neonatal nurses frequently care for babies who have been exposed in utero to potentially harmful substances, both licit and illicit. The risks to the fetus from nicotine, marijuana, alcohol, and opiates are significant. Adverse effects from environmental factors may confound pharmacologic effects of substances. Nurses are called to shift the perception of substance use disorder from that of willful harm to the fetus to that of an opportunity to provide treatment assistance that can positively affect child health and development. Concerns for unethical practices in the toxicology screening of pregnant women and their babies by risk factors that are unproven or disproven are discussed, and three goals of toxicology screening based on the ethical principles of justice and beneficence are proposed. This article will help equip neonatal nurses to fulfill their professional responsibility to advocate for just screening and referral practices in their institutions and communities.

Male Sex Associated With Increased Risk of Neonatal Abstinence Syndrome

BACKGROUND

Neonatal abstinence syndrome (NAS) is a postnatal opioid withdrawal syndrome. Factors associated with development of the syndrome are poorly understood; however, infant sex may influence the risk of NAS. Our objective was to determine if infant sex was associated with the development or severity of the syndrome in a large population-based cohort.

METHODS

This retrospective cohort study used vital statistics and prescription, outpatient, and inpatient administrative data for mothers and infants enrolled in the Tennessee Medicaid program between 2009 and 2011. Multivariable logistic regression models were used to evaluate the association between male sex and diagnosis of NAS, accounting for potential demographic and clinical confounders. NAS severity, as evidenced by hospital length of stay, was modeled by using negative binomial regression.

RESULTS

Of 102 695 infants, 927 infants were diagnosed with NAS (484 male subjects and 443 female subjects). Adjustments were made for the following: maternal age, race, and education; maternal hepatitis C infection, anxiety, or depression; in utero exposure to selective serotonin reuptake inhibitors and cigarettes; infant birth weight, small for gestational age, and year; and the interaction between opioid type and opioid amount. Male infants were more likely than female infants to be diagnosed with NAS (adjusted odds ratio, 1.18 [95% confidence interval, 1.05-1.33]) and NAS requiring treatment (adjusted odds ratio, 1.24 [95% confidence interval, 1.04-1.47]). However, there was no sex-based difference in severity for those diagnosed with NAS.

CONCLUSIONS

Treatment of NAS should be tailored to an infant's individual risk for the syndrome. Clinicians should be mindful that male sex is an important risk factor in the diagnosis of NAS.

The gestational foundation of sex differences in development and vulnerability

Despite long-standing interest in the role of sex on human development, the functional consequences of fetal sex on early development are not well-understood. Here we explore the gestational origins of sex as a moderator of development. In accordance with the focus of this special issue, we examine evidence for a sex differential in vulnerability to prenatal and perinatal risks. Exposures evaluated include those present in the external environment (e.g., lead, pesticides), those introduced by maternal behaviors (e.g., alcohol, opioid use), and those resulting from an adverse intrauterine environment (e.g., preterm birth). We also provide current knowledge on the degree to which sex differences in fetal neurobehavioral development (i.e., cardiac and motor patterns) are present prior to birth. Also considered are contemporaneous and persistent sex of fetus effects on the pregnant woman. Converging evidence confirms that infant and early childhood developmental outcomes of male fetuses exposed to prenatal and perinatal adversities are more highly impaired than those of female fetuses. In certain circumstances, male fetuses are both more frequently exposed to early adversities and more affected by them when exposed than are female fetuses. The mechanisms through which biological sex imparts vulnerability or protection on the developing nervous system are largely unknown. We consider models that implicate variation in maturation, placental functioning, and the neuroendocrine milieu as potential contributors. Many studies use sex as a control variable, some analyze and report main effects for sex, but those that report interaction terms for sex are scarce. As a result, the true scope of sex differences in vulnerability is unknown.

Identification of early developmental deficits in infants with prenatal heroin, methadone, and other opioid exposure

OBJECTIVE

Study aims to examine development in infants following prenatal heroin, methadone, and opioid exposure, which adversely affects central and autonomic nervous systems. Abrupt discontinuation results in neurologic and behavioral findings as Neonatal Abstinence Syndrome (NAS).

METHOD

Following NAS treatment, 28 infants (mean age 55 days [range 21-98 days], 57% male) were assessed using Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) Cognitive, Language, and Motor subscales. Outcomes were compared with a historical control.

RESULTS

Mean Language and Cognition scores were significantly lower (P < .001) in the NAS group. Distributions of scores for Language (P < .001) and Cognition (P = .022) were also significantly different between NAS and historical control groups.

CONCLUSION

Prenatal heroin, methadone, and other opioid exposure is associated with weaknesses in language and cognition. This information has important public health implications, drawing attention to an otherwise healthy infant population which may benefit from early intervention services.

Treating tobacco use disorder in pregnant women in medication-assisted treatment for an opioid use disorder: a systematic review

Smoking is associated with adverse effects on pregnancy and fetal development, yet 88-95% of pregnant women in medication-assisted treatment for an opioid use disorder smoke cigarettes. This review summarizes existing knowledge about smoking cessation treatments for pregnant women on buprenorphine or methadone, the two forms of medication-assisted treatment for opioid use disorder indicated for prenatal use. We performed a systematic review of the literature using indexed terms and key words to capture the concepts of smoking, pregnancy, and opioid substitution and found that only three studies met search criteria. Contingency management, an incentive based treatment, was the most promising intervention: 31% of participants achieved abstinence within the 12-week study period, compared to 0% in a non-contingent behavior incentive group and a group receiving usual care. Two studies of brief behavioral interventions resulted in reductions in smoking but not cessation. Given the growing number of pregnant women in medication-assisted treatment for an opioid use disorder and the negative consequences of smoking on pregnancy, further research is needed to develop and test effective cessation strategies for this group.

Time to initiation of treatment for neonatal abstinence syndrome in neonates exposed in utero to buprenorphine or methadone

BACKGROUND

The recommended standard of care calls for treating opioid-dependent pregnant women with methadone and observing neonates exposed in utero for five to seven postnatal days to see if treatment for neonatal abstinence syndrome (NAS) is needed. Data from a large multi-site randomized clinical trial comparing buprenorphine vs. methadone for the treatment of opioid dependence during pregnancy suggest buprenorphine-exposed neonates had less severe NAS, but may require pharmacologic treatment for NAS later than methadone-exposed neonates. The present study examined whether time to pharmacologic treatment initiation differed in a relatively large non-blinded clinical sample of buprenorphine- vs. methadone-exposed neonates treated for NAS.

METHODS

Medical records for 75 neonates exposed to buprenorphine (n=47) or methadone (n=28) in utero who required treatment for NAS were examined. Time elapsed between birth and initiation of pharmacologic treatment was calculated for each neonate and time to treatment initiation compared between groups.

RESULTS

Median time to treatment initiation (hours:minutes, IQR) was significantly later in buprenorphine- vs. methadone-exposed neonates (71:02, 44:21-96:27 vs. 34:12, 21:00-55:41, respectively, p<.001). Estimates of mean time to treatment initiation from parametric analyses that adjusted for maternal and neonatal characteristics were very similar (73:10 (95% CI: 61:00-87:18) vs. 42:36 (95% CI: 33:06-53:30), respectively, p=.0005). This difference was not dependent on maternal age or neonatal sex, gestational age, or birth weight.

CONCLUSIONS

These findings confirm results from randomized clinical trials, adding generality to the observation that buprenorphine-exposed neonates require treatment significantly later than methadone-exposed neonates.

Babies breaking bad: neonatal and iatrogenic withdrawal syndromes

PURPOSE OF REVIEW

This review will summarize the symptoms, evaluation, and treatment of neonatal and iatrogenic withdrawal syndromes.

RECENT FINDINGS

Buprenorphine is emerging as the drug of choice for maintaining opioid-dependent women during pregnancy, because of its association with less severe withdrawal symptoms. Recent findings suggest it may be the drug of choice for treating the opioid-exposed neonate as well.

SUMMARY

Healthcare workers should be cognizant of the risk factors for neonatal abstinence syndrome (NAS), as well as its symptoms, so that nonpharmalogic and pharmacologic therapies can be initiated. With increased emphasis on pain control in children, it is likely that iatrogenic withdrawal will continue to be a concern, and healthcare workers should understand the similarities and differences between this and NAS.

Neonatal abstinence syndrome: treatment and pediatric outcomes

Recent rise in rates of opiate replacement therapy among pregnant women have resulted in increasing number of infants requiring treatment for neonatal abstinence syndrome (NAS). Short-term and long-term developmental outcomes associated with prenatal opiate exposure are discussed, including symptoms and severity of NAS, and early cognitive and motor delays. Maternal and infant risk factors are discussed, and include patterns of maternal substance use during pregnancy, genetic risk, polysubstance exposure pharmacological treatment for NAS and breastfeeding. The importance of characterizing corollary environmental risk factors is also considered.

Predicting treatment for neonatal abstinence syndrome in infants born to women maintained on opioid agonist medication

AIM

To identify factors that predict the expression of neonatal abstinence syndrome (NAS) in infants exposed to methadone or buprenorphine in utero.

DESIGN AND SETTING

Multi-site randomized clinical trial in which infants were observed for a minimum of 10 days following birth, and assessed for NAS symptoms by trained raters.

PARTICIPANTS

A total of 131 infants born to opioid dependent mothers, 129 of whom were available for NAS assessment.

MEASUREMENTS

Generalized linear modeling was performed using maternal and infant characteristics to predict: peak NAS score prior to treatment, whether an infant required NAS treatment, length of NAS treatment and total dose of morphine required for treatment of NAS symptoms.

FINDINGS

Of the sample, 53% (68 infants) required treatment for NAS. Lower maternal weight at delivery, later estimated gestational age (EGA), maternal use of selective serotonin re-uptake inhibitors (SSRIs), vaginal delivery and higher infant birthweight predicted higher peak NAS scores. Higher infant birthweight and greater maternal nicotine use at delivery predicted receipt of NAS treatment for infants. Maternal use of SSRIs, higher nicotine use and fewer days of study medication received also predicted total dose of medication required to treat NAS symptoms. No variables predicted length of treatment for NAS.

CONCLUSIONS

Maternal weight at delivery, estimated gestational age, infant birthweight, delivery type, maternal nicotine use and days of maternal study medication received and the use of psychotropic medications in pregnancy may play a role in the expression of neonatal abstinence syndrome severity in infants exposed to either methadone or buprenorphine.

The Opioid dependent mother and newborn dyad: non-pharmacologic care

Opioid dependent pregnant and post-partum women and their infants are a complex and vulnerable population requiring individualized, comprehensive and multidisciplinary treatment. Though methadone maintenance in the setting of comprehensive service provision during pregnancy significantly improves pregnancy outcomes for opioid dependent women, its use has implications for the infant, most notably the Neonatal Abstinence Syndrome (NAS). NAS is comprised of physiologic signs and behaviors that indicate a dysfunctional regulation of the central and autonomic nervous systems, and is variable in its expression in affected infants. The disorganized rather than adaptive behaviors displayed by each infant undergoing the effects of in-utero opioid exposure may impair basic functions such as feeding, sleeping, and the ability to be alert and communicate clear cues to caregivers. Understanding and responding to neurobehavioral dysfunction of the newborn may help to promote the infant's self-organization and self-regulating abilities. However, the substance abusing mother's physical and psychological wellbeing may be debilitated in the perinatal period, and her ability to recognize and respond to the newborn's cues may be limited. A multi-tiered comprehensive assessment and intervention of the methadone-maintained mother, her child, and the mother/infant dyad can improve early maternal nurturing interactions, a crucial component of early infant development, particularly in this vulnerable population. The purpose of this article is to review the contribution of maternal opioid dependency to the difficulties experienced by the mother-infant dyad and their treatment providers in the postnatal period, and the non-pharmacological treatment of the infants with suggestions for practical measures with emphasis on the treatment of the mother and baby as an interactional dyad.

Pharmacologic management of the opioid neonatal abstinence syndrome

Opioid use in pregnant women has increased over the last decade. Following birth, infants with in utero exposure demonstrate signs and symptoms of withdrawal known as the neonatal abstinence syndrome (NAS). Infants express a spectrum of disease, with most requiring the administration of pharmacologic therapy to ensure proper growth and development. Treatment often involves prolonged hospitalization. There is a general lack of high-quality clinical trial data to guide optimal therapy, and significant heterogeneity in treatment approaches. Emerging trends in the treatment of infants with NAS include the use of sublingual buprenorphine, transition to outpatient therapy, and pharmacogenetic risk stratification.

Methadone and perinatal outcomes: a prospective cohort study

AIMS

  Methadone use in pregnancy has been associated with adverse perinatal outcomes and neonatal abstinence syndrome (NAS). This study aimed to examine perinatal outcomes and NAS in relation to (i) concomitant drug use and (ii) methadone dose.

DESIGN

  Prospective cohort study.

SETTING

  Two tertiary care maternity hospitals.

PARTICIPANTS

  A total of 117 pregnant women on methadone maintenance treatment recruited between July 2009 and July 2010.

MEASUREMENTS

  Information on concomitant drug use was recorded with the Addiction Severity Index. Perinatal outcomes included pre-term birth (<37 weeks' gestation), small-for-gestational-age (<10th centile) and neonatal unit admission. NAS outcomes included: incidence of medically treated NAS, peak Finnegan score, cumulative dose of NAS treatment and duration of hospitalization.

FINDINGS

  Of the 114 liveborn infants 11 (9.6%) were born pre-term, 49 (42.9%) were small-for-gestational-age, 56 (49.1%) had a neonatal unit admission and 29 (25.4%) were treated medically for NAS. Neonates exposed to methadone-only had a shorter hospitalization than those exposed to methadone and concomitant drugs (median 5.0 days versus 6.0 days, P = 0.03). Neonates exposed to methadone doses ≥80 mg required higher cumulative doses of morphine treatment for NAS (median 13.2 mg versus 19.3 mg, P = 0.03). The incidence and duration of NAS did not differ between the two dosage groups.

CONCLUSIONS

  The incidence and duration of the neonatal abstinence syndrome is not associated with maternal methadone dose, but maternal opiate, benzodiazepine or cocaine use is associated with longer neonatal hospitalization.

Maternal drug use and its effect on neonates: a population-based study in Washington State

OBJECTIVE

To estimate the effect of maternal illicit and prescription drug use on neonates in Washington State between 2000 and 2008.

METHODS

We used state-linked birth certificate and hospital discharge (mother and neonate) data to calculate prenatal drug exposure and neonatal abstinence syndrome rates, and compared state neonatal abstinence syndrome rates with national-level data from the Nationwide Inpatient Sample. We identified the drugs of exposure, examined predictors of drug exposure and neonatal abstinence syndrome, and assessed perinatal outcomes among drug-exposed and neonatal abstinence syndrome-diagnosed neonates compared with unexposed neonates.

RESULTS

Drug exposure and neonatal abstinence syndrome rates increased significantly between 2000 and 2008, neonatal abstinence syndrome rates being consistently higher than national figures (3.3 compared with 2.8 per 1,000 births in 2008; P<.05). The proportion of neonatal abstinence syndrome-diagnosed neonates exposed prenatally to opioids increased from 26.4% in 2000 to 41.7% in 2008 (P<.05). Compared with unexposed neonates, drug-exposed and neonatal abstinence syndrome-diagnosed neonates had a lower mean birth weight, longer birth hospitalization, were more likely to be born preterm, experience feeding problems, and have respiratory conditions (all P<.001).

CONCLUSION

Maternal use of illicit and prescription drugs was associated with considerable neonatal morbidity and significantly higher rates of drug exposure and neonatal abstinence syndrome in recent years. Data suggest that opioid analgesics contributed to the increase in prenatal drug exposure and neonatal abstinence syndrome in Washington State. In accordance with current guidelines, our findings emphasize the need for clinicians to screen pregnant women for illicit and prescription drug use and minimize use of opioid analgesics during pregnancy.

LEVEL OF EVIDENCE

II.

Pregnancies exposed to methadone, methadone and other illicit substances, and poly-drugs without methadone: a comparison of fetal neurobehaviors and infant outcomes

BACKGROUND

It is suspected that there is a continuum of impairment among prenatally drug-exposed infants, such that opioid and/or poly-drug exposure confers the highest risk for adverse neonatal outcomes than other classes of substances or single substance exposures. Suitable control groups are difficult to identify. This study compared fetal neurobehavioral development and infant outcomes in offspring of three groups of pregnant women in drug treatment. Exposure groups include: Methadone+other illicit substances (MM+Poly) and two groups currently abstinent for poly drug exposures: Methadone only (MM/A) and Non-Methadone (NM/A).

METHODS

Forty-nine women (19 MM+Poly, 18 MM/A, and 12 NM/A) underwent fetal monitoring at 36 weeks gestation at peak and trough levels of methadone (MM+Poly; MM/A) or at comparable morning and afternoon times (NM/A). Fetal heart rate (FHR), heart rate variability (FHRV) and motor activity (FM) data were collected. Infant measures included birth outcomes and Neonatal Abstinence Syndrome (NAS) assessment.

RESULTS

As compared to the NM/A group, cardiac measures were decreased in methadone-exposed fetuses at peak levels. FHR was significantly more suppressed in the MM+Poly group. FM was significantly lower in the MM/A vs. the NM/A group at both peak and trough, indicative of more persistent exposure effects. The MM+Poly group delivered 1 week earlier and required NAS pharmacological treatment twice as often as the MM/A group.

CONCLUSIONS

Results support the notion that poly-drug exposure may potentiate the effects of methadone on the fetus and infant and highlights the need for intensified treatment for methadone-maintained women who abuse other substances.

Cardiac autonomic modulation during methadone therapy among heroin users: a pilot study

BACKGROUND

Methadone therapy benefits heroin users in both the medical and psychosocial dimensions. However, both heroin and methadone have cardiac toxicity. Only limited information is available describing the changes in cardiac autonomic function of heroin users and effects of methadone therapy. We conduct the current study to explore the cardiac vagal function in heroin users as well as the impact of lapse and methadone therapy.

METHODS

80 heroin users from a methadone therapy clinic were distributed into 31 compliant and 49 incompliant patients according to whether they lapsed into heroin use within 10 days. 40 healthy control subjects were recruited from the community. Participants underwent electrocardiographic recordings and the heroin users were further investigated before and after methadone therapy. Spectral analysis of heart rate variability (HRV) was computed for cardiac parasympathetic modulation (high-frequency power, HF) and cardiac sympathetic modulation (normalized low-frequency power, LF%).

RESULTS

The baseline HRV parameters found lower HF values for heroin users and lower RR interval values for patients with a recent lapse compared with the healthy control subjects. After 1h of methadone administration, heroin users who had lapsed showed a significant increase in HF but the heroin users who had not lapsed did not.

CONCLUSION

Our findings suggest that heroin users show decreased cardiac vagal activity and that methadone therapy immediately facilitates vagal regulation in patients with a recent lapse. The differential patterns of autonomic alteration under methadone between those with and without lapse might offer an objective measure of lapse.

Neonatal abstinence syndrome

PURPOSE OF REVIEW

This review will discuss the complex nature of maternal and other factors that can affect the infant's display of neonatal abstinence syndrome (NAS), clinical presentation and treatment of NAS, and the impact of recent findings on future directions for research.

RECENT FINDINGS

NAS has traditionally been described as a constellation of signs/symptoms displayed by the neonate upon withdrawal of gestational opioid exposure; however, recent research has advanced our understanding of this disorder. Other psychoactive substances, such as increasingly prescribed serotonin reuptake inhibitors, may produce an independent or synergistic discontinuation syndrome. The wide variability in NAS presentation has generated interest in the interplay of prenatal and postnatal environmental and genetic factors that may moderate or mediate its expression. Finally, recent advances in the treatment of opioid-dependent pregnant women have suggested buprenorphine as an alternative treatment to methadone during pregnancy, largely due to reduced NAS severity in exposed neonates.

SUMMARY

Physicians should be aware of the complexity of the maternal, fetal, and infant factors that combine to create the infant's display of NAS, and incorporate these aspects into comprehensive assessment and care of the dyad. Further research regarding the pathophysiology and treatment of NAS is warranted.

Cigarette Smoking and Neonatal Outcomes in Depressed and Non-Depressed Opioid-Dependent Agonist-Maintained Pregnant Patients

AIMS: To investigate whether cigarette smoking and/or depression contribute to neonatal abstinence syndrome (NAS) severity. DESIGN: Cohort study analyzing data from a randomized, controlled trial of methadone versus buprenorphine. SETTING: Seven study sites that randomized patients to study conditions and provided comprehensive addiction treatment to pregnant patients. PARTICIPANTS: 119 of 131 opioid-dependent pregnant patients who completed the MOTHER study. MEASUREMENTS: Smoking data and depression status were obtained from the Addiction Severity Index and Mini International Neuropsychiatric Interview, respectively. Neonatal outcomes (birth weight, preterm delivery and NAS pharmacologic treatment) were collected from the medical charts. Study site was a fixed-effect factor in all analyses. FINDINGS: Cigarette smoking was reported by 94% of participants and depression identified in 35%. Smoking was associated with low birth weight, preterm delivery, and NAS pharmacologic treatment in both depressed and non-depressed participants. The association between smoking and NAS treatment differed significantly between depressed and non-depressed participants. Among non-depressed participants, adjusting for site and illicit drug use, each additional average cigarette per day (CPD) increased the odds of NAS treatment by 12% [95%CI: (1.02-1.23), p=0.02]. Among depressed participants, each additional average CPD did not statistically increase the odds of NAS treatment [OR: 0.94, 95% CI: (0.84-1.04), p=0.23]. CONCLUSIONS: These results are consistent with the hypothesis that NAS expression is influenced by many factors. The relationship between CPD and NAS pharmacologic treatment is attenuated among depressed women in this study for reasons currently unknown. Further investigations are needed to clarify the complex relationships among maternal smoking, depression, and NAS.

Methadone and perinatal outcomes: a retrospective cohort study

OBJECTIVE

The purpose of this study was to examine the relationship among methadone maintenance treatment, perinatal outcomes, and neonatal abstinence syndrome.

STUDY DESIGN

This was a retrospective cohort study of 61,030 singleton births at a large maternity hospital from 2000-2007.

RESULTS

There were 618 (1%) women on methadone at delivery. Methadone-exposed women were more likely to be younger, to book late for antenatal care, and to be smokers. Methadone exposure was associated with an increased risk of very preterm birth <32 weeks of gestation (adjusted odds ratio [aOR], 2.47; 95% confidence interval [CI], 1.40-4.34), being small for gestational age <10th percentile (aOR, 3.27; 95% CI, 2.49-4.28), admission to the neonatal unit (aOR, 9.14; 95% CI, 7.21-11.57), and diagnosis of a major congenital anomaly (aOR, 1.94; 95% CI, 1.10-3.43). There was a dose-response relationship between methadone and neonatal abstinence syndrome.

CONCLUSION

Methadone exposure is associated with an increased risk of adverse perinatal outcomes, even when known adverse sociodemographic factors have been accounted for. Methadone dose at delivery is 1 of the determinants of neonatal abstinence syndrome.

Methadone dose and neonatal abstinence syndrome-systematic review and meta-analysis

AIM

To determine if there is a relationship between maternal methadone dose in pregnancy and the diagnosis or medical treatment of neonatal abstinence syndrome (NAS).

METHODS

PubMed, EMBASE, the Cochrane Library and PsychINFO were searched for studies reporting on methadone use in pregnancy and NAS (1966-2009). The relative risk (RR) of NAS was compared for methadone doses above versus below a range of cut-off points. Summary RRs and 95% confidence intervals (CI) were estimated using random effects meta-analysis. Sensitivity analyses explored the impact of limiting meta-analyses to prospective studies or studies using an objective scoring system to diagnose NAS.

RESULTS

A total of 67 studies met inclusion criteria for the systematic review; 29 were included in the meta-analysis. Any differences in the incidence of NAS in infants of women on higher compared with lower doses were statistically non-significant in analyses restricted to prospective studies or to those using an objective scoring system to diagnose NAS.

CONCLUSIONS

Severity of the neonatal abstinence syndrome does not appear to differ according to whether mothers are on high- or low-dose methadone maintenance therapy.

Infant neurobehavior following prenatal exposure to methadone or buprenorphine: results from the neonatal intensive care unit network neurobehavioral scale

This study examined the neurobehavioral functioning of neonates prenatally exposed to methadone (n = 11) or buprenorphine (n = 10), who underwent the Neonatal Intensive Care Unit Network Neurobehavioral Scale (NNNS) examinations on days 3, 5, 7, 10, and 14 post-delivery. Linear mixed model analyses revealed that NNNS scores of arousal and excitability showed significant differences between medications over time. Compared to neonates who did not require medication to treat neonatal abstinence syndrome (NAS), neonates receiving pharmacotherapy for NAS showed differences over time in quality of movement, excitability, and lethargy. Results suggest the NNNS may detect subtle differences over time between both neonates prenatally exposed to methadone or buprenorphine and neonates pharmacologically treated or untreated for NAS.

Methadone and buprenorphine toxicity in children

Recent years have seen very large increases in the prescribing of methadone and buprenorphine formulations for treatment of opioid addiction as well as the increasing utilization of methadone for the treatment of chronic pain. Coincident with the rise in the prescribing of these drugs has been a substantial increase in pediatric opioid toxicities and adverse events. This review will address the current state of methadone- and buprenorphine-related adverse events in children in the United States. We will also discuss treatment of opioid toxicity in pediatric populations and make recommendations aimed at reducing these occurrences.

Relationship between maternal methadone dose at delivery and neonatal abstinence syndrome

OBJECTIVE

To estimate the relationship between maternal methadone dose and the incidence of neonatal abstinence syndrome (NAS).

STUDY DESIGN

We performed a retrospective cohort study of pregnant women treated with methadone for opiate addiction who delivered live-born neonates between 1996 and 2006. Four dose groups, on the basis of total daily methadone dose, were compared (<or=80 mg/d, 81-120 mg/d, 121-160 mg/d, and >160 mg/d). The primary outcome was treatment for NAS. Symptoms of NAS were objectively measured with the Finnegan scoring system, and treatment was initiated for a score>24 during the prior 24 hours.

RESULTS

A total of 330 women treated with methadone and their 388 offspring were included. Average methadone dose at delivery was 117+/-50 mg/d (range, 20-340 mg/d). Overall, 68% of infants were treated for NAS. Of infants exposed to methadone doses<or=80 mg/d, 81-120 mg/d, 121-160 mg/d, and >160 mg/d, treatment for NAS was initiated for 68%, 63%, 70%, and 73% of neonates, respectively (P=.48). The rate of maternal illicit opiate abuse at delivery was 26%, 28%, 19%, and 11%, respectively (P=.04).

CONCLUSION

No correlation was found between maternal methadone dose and rate of NAS. However, higher doses of methadone were associated with decreased illicit opiate abuse at delivery.

Infant autonomic functioning and neonatal abstinence syndrome

BACKGROUND

Neonatal abstinence syndrome (NAS) expression is widely variable among affected infants and the reasons for this variability are largely unknown; mechanisms that predispose infants to NAS expression are not understood. It has been postulated that the regulatory problems of prenatally drug exposed infants are manifested in dysfunctional vagal regulation of autonomic processes. The current study examines whether cardiac vagal tone, an indicator of parasympathetic neuroregulation, provides a marker for autonomic dysregulation subsequently expressed as NAS in prenatally opioid-exposed newborns.

METHODS

Heart period (HP) and cardiac vagal tone (V) were derived from electrocardiogram data collected from 64 methadone-exposed infants on postnatal days 1 and 3. The postpartum NAS course was assessed serially.

RESULTS

Infants with lower V on day 1 had significantly higher NAS symptomatology on day 3. Boys had more severe NAS symptoms than girls through the first 4 days of life and, among infants receiving pharmacologic treatment for NAS, boys required longer treatment course and hospitalizations. Greater poly-drug exposure, detected through toxicology screening throughout pregnancy, and cocaine use in particular, were associated with lower V and shorter HP (faster heart rate) in newborns. Multiple regression models accounted for 25-35% of the variance in NAS symptoms and duration of hospitalization in methadone-exposed infants. Significant predictors included infant sex, SSRI/SNRI use, and cigarette smoking.

CONCLUSIONS

Results support the hypothesis of a biologic vulnerability of autonomic regulatory functioning in methadone-exposed infants and greater male infant vulnerability to maternal methadone use.

Maternal methadone dose during pregnancy and infant clinical outcome

In recent decades there has been an increase in the methadone dosages prescribed for opioid dependent women during pregnancy. Using prospective longitudinal data from a cohort of 32 methadone exposed and 42 non-methadone exposed infants, this study examined the relationship between maternal methadone dose during pregnancy and a range of infant clinical outcomes. Of particular interest was the extent to which any observed associations might reflect the direct causal effects of maternal methadone dose and/or the confounding effects of adverse maternal lifestyle factors correlated with methadone use during pregnancy. Findings revealed the presence of clear linear relationships between the mean methadone dose prescribed for mothers during pregnancy and a range of adverse infant clinical outcomes. With increasing maternal methadone dose there was a corresponding increase in infants' risk of being born preterm, being symmetrically smaller, spending longer periods in hospital and the need for treatment for Neonatal Abstinence Syndrome. After due allowance for potentially confounding maternal health and lifestyle factors, maternal methadone dose during pregnancy remained a significant predictor of preterm birth, growth, and the duration of infant hospitalization post delivery. These findings suggest a need to examine more closely the potential impacts of recent trends towards the use of higher methadone dose levels during pregnancy.

Prenatal methadone exposure and neonatal neurobehavioral functioning

Opioid-exposed infants display a wide and variable range of dysregulated neurobehavioral functioning, but the regulatory difficulties experienced by these infants outside the defined clusters of neonatal abstinence syndrome (NAS) have not been well described and may have implications for the infant's developmental course. This study describes the neurobehavioral functioning of neonates prenatally exposed to methadone, using the NICU Network Neurobehavioral Scale (NNNS), and explores the relationships between maternal factors and infant functioning. The relationship between NNNS measures, NAS severity, and need for pharmacotherapy for NAS was also evaluated. Infants who required pharmacologic treatment for NAS showed more dysregulated behavior and signs of stress and abstinence as indicated by NNNS scores, but NNNS scores were not significantly correlated with maternal methadone dose. The determination of the range of the methadone-exposed infant's neurobehavioral repertoire could guide the optimal treatment of all such infants, particularly those requiring only nonpharmacologic care.

Maternal methadone dosing schedule and fetal neurobehaviour

OBJECTIVE

Daily methadone maintenance is the standard of care for opiate dependency during pregnancy. Previous research has indicated that single-dose maternal methadone administration significantly suppresses fetal neurobehaviours. The purpose of this study was to determine if split-dosing would have less impact on fetal neurobehaviour than single-dose administration.

METHODS

Forty methadone-maintained women were evaluated at peak and trough maternal methadone levels on single- and split-dosing schedules. Monitoring sessions occurred at 36- and 37-weeks gestation in a counterbalanced study design. Fetal measures included heart rate, variability, accelerations, motor activity and fetal movement-heart rate coupling (FM-FHR). Maternal measures included heart period, variability, skin conductance, respiration and vagal tone. Repeated measure analysis of variance was used to evaluate within-subject changes between split- and single-dosing regimens.

RESULTS

All fetal neurobehavioural parameters were suppressed by maternal methadone administration, regardless of dosing regimen. Fetal parameters at peak were significantly lower during single versus split methadone administration. FM-FHR coupling was less suppressed from trough to peak during split-dosing versus single-dosing. Maternal physiologic parameters were generally unaffected by dosing condition.

CONCLUSION

Split-dosed fetuses displayed less neurobehavioural suppression from trough to peak maternal methadone levels as compared with single-dosed fetuses. Split-dosing may be beneficial for methadone-maintained pregnant women.

Treatment of opioid-dependent pregnant women: clinical and research issues

This article addresses common questions that clinicians face when treating pregnant women with opioid dependence. Guidance, based on both research evidence and the collective clinical experience of the authors, which include investigators in the Maternal Opioid Treatment: Human Experimental Research (MOTHER) project, is provided to aid clinical decision making. The MOTHER project is a double-blind, double-dummy, flexible-dosing, parallel-group clinical trial examining the comparative safety and efficacy of methadone and buprenorphine for the treatment of opioid dependence in pregnant women and their neonates. The article begins with a discussion of appropriate assessment during pregnancy and then addresses clinical management stages including maintenance medication selection, induction, and stabilization; opioid agonist medication management before, during, and after delivery; pain management; breast-feeding; and transfer to aftercare. Lastly, other important clinical issues including managing co-occurring psychiatric disorders and medication interactions are discussed.