Concepts in teratology and developmental toxicology derived from animal research

Influence of prenatal cannabinoid exposure on early development and beyond

Public perception surrounding whether cannabis use is harmful during pregnancy often diverges greatly from the recommendations of doctors and healthcare providers. In contrast to the medical guidance of abstinence before, during, and after pregnancy, many women of reproductive age believe cannabis use during pregnancy is associated with little potential harm. Legalization and social cues support public perceptions that cannabis use during pregnancy is safe. Moreover, pregnant women may consider cannabis to be a safe alternative for treating pregnancy related ailments, including morning sickness. Compounding the problem is a lack of medical and federal guidance on safe, low, or high-risk levels of cannabis use. These issues mirror the continuing debate surrounding alcohol use and health, in particular, whether there are safe or lower risk levels of alcohol consumption during pregnancy. Clinical studies to date suffer from several limitations. First, most human studies are correlative in nature, meaning that causal associations cannot be made between in utero cannabis exposure and health and behavioral outcomes later in life. Due to obvious ethical constraints, it is not possible to randomly assign pregnant mothers to cannabis or other drug exposure conditions-a requirement needed to establish causality. In addition, clinical studies often lack quantitative information on maternal exposure (i.e., dose, frequency, and duration), include a small number of individuals, lack replication of outcome measures across cohorts, rely on self-report to establish maternal drug use, and suffer from unmeasured or residual confounding factors. Causal associations between maternal cannabis exposure and offspring outcomes are possible in preclinical cohorts but there is a large amount of heterogeneity across study designs and developmental differences between rodents and humans may limit translatability. In this review, we summarize research from human and preclinical models to provide insight into potential risks associated with prenatal cannabinoid exposure (PCE). Finally, we highlight gaps in knowledge likely to contribute to the growing divide between medical guidance and public attitudes regarding cannabis use during pregnancy.

Morphine Perinatal Exposure Induces Long-Lasting Negative Emotional States in Adult Offspring Rodents

Psychoactive substances during pregnancy and lactation is a key problem in contemporary society, causing social, economic, and health disturbance. In 2010, about 30 million people used opioid analgesics for non-therapeutic purposes, and the prevalence of opioids use during pregnancy ranged from 1% to 21%, representing a public health problem. This study aimed to evaluate the long-lasting neurobehavioral and nociceptive consequences in adult offspring rats and mice exposed to morphine during intrauterine/lactation periods. Pregnant rats and mice were exposed subcutaneously to morphine (10 mg/kg/day) during 42 consecutive days (from the first day of pregnancy until the last day of lactation). Offspring were weighed on post-natal days (PND) 1, 5, 10, 15, 20, 30, and 60, and behavioral tasks (experiment 1) or nociceptive responses (experiment 2) were assessed at 75 days of age (adult life). Morphine-exposed female rats displayed increased spontaneous locomotor activity. More importantly, both males and female rats perinatally exposed to morphine displayed anxiety- and depressive-like behaviors. Morphine-exposed mice presented alterations in the nociceptive responses on the writhing test. This study showed that sex difference plays a role in pain threshold and that deleterious effects of morphine during pre/perinatal periods are nonrepairable in adulthood, which highlights the long-lasting clinical consequences related to anxiety, depression, and nociceptive disorders in adulthood followed by intrauterine and lactation morphine exposure.

Maternal cannabis use in pregnancy and child neurodevelopmental outcomes

Cannabis use in pregnancy has increased^1,2, and many women continue to use it throughout pregnancy³. With the legalization of recreational cannabis in many jurisdictions, there is concern about potentially adverse childhood outcomes related to prenatal exposure⁴. Using the provincial birth registry containing information on cannabis use during pregnancy, we perform a retrospective analysis of all live births in Ontario, Canada, between 1 April 2007 and 31 March 2012. We link pregnancy and birth data to provincial health administrative databases to ascertain child neurodevelopmental outcomes. We use matching techniques to control for confounding and Cox proportional hazards regression models to examine associations between prenatal cannabis use and child neurodevelopment. We find an association between maternal cannabis use in pregnancy and the incidence of autism spectrum disorder in the offspring. The incidence of autism spectrum disorder diagnosis was 4.00 per 1,000 person-years among children with exposure compared to 2.42 among unexposed children, and the fully adjusted hazard ratio was 1.51 (95% confidence interval: 1.17-1.96) in the matched cohort. The incidence of intellectual disability and learning disorders was higher among offspring of mothers who use cannabis in pregnancy, although less statistically robust. We emphasize a cautious interpretation of these findings given the likelihood of residual confounding.

Prenatal cocaine exposure: Direct and indirect associations with 21-year-old offspring substance use and behavior problems

BACKGROUND

Prenatal cocaine exposure (PCE) has been linked to child/adolescent behavior problems and substance use in several longitudinal cohort studies. It is unclear whether these effects extend into adulthood and influence young adult behavior problems and substance use and, if so, whether they are mediated by childhood and adolescent experiences.

METHODS

These data are from an ongoing longitudinal study of individuals born to women who were recruited early in pregnancy. Trimester-specific data on prenatal drug exposure were obtained. Caregivers and offspring were assessed at delivery and at 1, 3, 7, 10, 15, and 21 years postpartum. This report is from age 21, when 225 offspring (52% females; 54% African American, 46% Caucasian) reported on behavior problems, emotion regulation, and substance use.

RESULTS

There were significant direct associations between PCE and early initiation of marijuana, 21-year emotion regulation problems, arrest history, and Conduct Disorder. The relation between PCE and young adult internalizing behavior was mediated by adolescent mood symptoms. The association between PCE and 21-year marijuana use was mediated by early initiation of marijuana use.

CONCLUSIONS

PCE has both direct and indirect long-term associations with young adult development. Using statistical models that considered the complex interrelationships among PCE and adult outcomes, we demonstrated that the direct effects of PCE on young adult emotion regulation problems, arrest history, and Conduct Disorder are not completely explained by earlier adolescent behavior. Moreover, the analyses suggesting mediated pathways from PCE to young adult problems identify crucial variables to target interventions for exposed children and adolescents.

Association of prenatal cocaine exposure, childhood maltreatment, and responses to stress in adolescence

BACKGROUND

Prenatal cocaine exposure (PCE) may alter responses to stress. Children with PCE tend to grow up in suboptimal caregiving environments, conducive to child maltreatment (CM). Guided by the diathesis-stress model, the present study examined differences in self-reported responses to stress and coping in adolescents with and without PCE and explored whether childhood maltreatment (CM) moderated the effects of PCE.

METHODS

Adolescents (N=363; 184 PCE, 179 non-cocaine exposed (NCE)), primarily African-American and of low socioeconomic status, were prospectively enrolled in a longitudinal study at birth. The Responses to Stress Questionnaire was used to assess volitional coping (primary control, secondary control, disengagement) and involuntary responses (involuntary engagement, involuntary disengagement) to stress at the 15- and 17-year follow-up visits. CM was assessed retrospectively at age 17 using the Juvenile Victimization Questionnaire.

RESULTS

Findings from longitudinal mixed model analyses indicated that PCE was associated with poorer coping strategies only among adolescents with a history of CM. Adolescents with PCE who experienced CM reported less dominant use of primary (e.g., problem solving, emotional regulation) and secondary control (e.g., cognitive restructuring) and more dominant use of disengagement (e.g., denial, avoidance) and involuntary disengagement (e.g., inaction) than adolescents with PCE who did not experience CM or NCE adolescents regardless of CM. CM was associated with more dominant use of involuntary engagement (e.g., intrusive thoughts).

CONCLUSIONS

PCE may increase sensitivity to CM, predisposing increased vulnerability to environmental risk. Continued studies into adulthood will elucidate how coping and involuntary stress responses affect social, vocational, and behavioral adjustment.

Prenatal cannabis exposure - The "first hit" to the endocannabinoid system

As more states and countries legalize medical and/or adult recreational marijuana use, the incidences of prenatal cannabis exposure (PCE) will likely increase. While young people increasingly view marijuana as innocuous, marijuana preparations have been growing in potency in recent years, potentially creating global clinical, public health, and workforce concerns. Unlike fetal alcohol spectrum disorder, there is no phenotypic syndrome associated with PCE. There is also no preponderance of evidence that PCE causes lifelong cognitive, behavioral, or functional abnormalities, and/or susceptibility to subsequent addiction. However, there is compelling circumstantial evidence, based on the principles of teratology and fetal malprogramming, suggesting that pregnant women should refrain from smoking marijuana. The usage of marijuana during pregnancy perturbs the fetal endogenous cannabinoid signaling system (ECSS), which is present and active from the early embryonic stage, modulating neurodevelopment and continuing this role into adulthood. The ECSS is present in virtually every brain structure and organ system, and there is also evidence that this system is important in the regulation of cardiovascular processes. Endocannabinoids (eCBs) undergird a broad spectrum of processes, including the early stages of fetal neurodevelopment and uterine implantation. Delta-9-tetrahydrocannabinol (THC), the psychoactive chemical in cannabis, enters maternal circulation, and readily crosses the placental membrane. THC binds to CB receptors of the fetal ECSS, altering neurodevelopment and possibly rewiring ECSS circuitry. In this review, we discuss the Double-Hit Hypothesis as it relates to PCE. We contend that PCE, similar to a neurodevelopmental teratogen, delivers the first hit to the ECSS, which is compromised in such a way that a second hit (i.e., postnatal stressors) will precipitate the emergence of a specific phenotype. In summary, we conclude that perturbations of the intrauterine milieu via the introduction of exogenous CBs alter the fetal ECSS, predisposing the offspring to abnormalities in cognition and altered emotionality. Based on recent experimental evidence that we will review here, we argue that young women who become pregnant should immediately take a "pregnant pause" from using marijuana.

At the Tip of an Iceberg: Prenatal Marijuana and Its Possible Relation to Neuropsychiatric Outcome in the Offspring

Endocannabinoids regulate brain development via modulating neural proliferation, migration, and the differentiation of lineage-committed cells. In the fetal nervous system, (endo)cannabinoid-sensing receptors and the enzymatic machinery of endocannabinoid metabolism exhibit a cellular distribution map different from that in the adult, implying distinct functions. Notably, cannabinoid receptors serve as molecular targets for the psychotropic plant-derived cannabis constituent Δ(9)-tetrahydrocannainol, as well as synthetic derivatives (designer drugs). Over 180 million people use cannabis for recreational or medical purposes globally. Recreational cannabis is recognized as a niche drug for adolescents and young adults. This review combines data from human and experimental studies to show that long-term and heavy cannabis use during pregnancy can impair brain maturation and predispose the offspring to neurodevelopmental disorders. By discussing the mechanisms of cannabinoid receptor-mediated signaling events at critical stages of fetal brain development, we organize histopathologic, biochemical, molecular, and behavioral findings into a logical hypothesis predicting neuronal vulnerability to and attenuated adaptation toward environmental challenges (stress, drug exposure, medication) in children affected by in utero cannabinoid exposure. Conversely, we suggest that endocannabinoid signaling can be an appealing druggable target to dampen neuronal activity if pre-existing pathologies associate with circuit hyperexcitability. Yet, we warn that the lack of critical data from longitudinal follow-up studies precludes valid conclusions on possible delayed and adverse side effects. Overall, our conclusion weighs in on the ongoing public debate on cannabis legalization, particularly in medical contexts.

Effects of prenatal cocaine exposure on early sexual behavior: Gender difference in externalizing behavior as a mediator

BACKGROUND

Prenatal cocaine exposure (PCE) is associated with increased risk for externalizing behavior problems; childhood externalizing behavior problems are linked with subsequent early sexual behavior. The present study examined the effects of PCE on early sexual initiation (sexual intercourse prior to age 15) and whether externalizing behavior in preadolescence mediated the relationship.

METHODS

Three hundred fifty-four (180 PCE and 174 non-cocaine exposed; 192 girls, 142 boys), primarily African-American, low socioeconomic status, 15-year-old adolescents participated in a prospective longitudinal study. Adolescents' sexual behavior was assessed at 15 years using the Youth Risk Behavior Surveillance System. Externalizing behavior was assessed at 12 years using the Youth Self-Report.

RESULTS

Logistic regression models indicated that adolescents with PCE (n=69, 38%) were 2.2 times more likely (95% CI=1.2-4.1, p<.01) to engage in early sexual intercourse than non-exposed peers (n=49, 28%) controlling for covariates. This relationship was fully mediated by self-reported externalizing behavior in girls but not in boys, suggesting childhood externalizing behavior as a gender moderated mediator. Blood lead level during preschool years was also related to a greater likelihood of early sexual intercourse (OR=2.6, 95% CI=1.4-4.7, p<.002). Greater parental monitoring decreased the likelihood of early sexual intercourse, while violence exposure increased the risk.

CONCLUSIONS

PCE is related to early sexual intercourse, and externalizing behavior problems mediate PCE effects in female adolescents. Interventions targeting externalizing behavior may reduce early sexual initiation and thereby reduce HIV risk behaviors and early, unplanned pregnancy in girls with PCE.

Prenatal Maternal Substance Use and Offspring Outcomes

Evidence from both human and preclinical studies seems to indicate that maternal smoking, alcohol drinking, or other drug use during pregnancy can affect offspring outcomes. It also suggests that maternal substance use during pregnancy is a major preventable cause of adverse infant outcomes. Nonetheless, more recent studies applying genetically sensitive designs cast some doubt on the causality of the relationship between prenatal maternal substance use and infant and child behavioral outcomes. In this review, recent findings in this field of research are provided, with attention to correlated risk factors of maternal substance use during pregnancy and preclinical studies focusing on plausible biological pathways. Next, evidence-based interventions targeting maternal substance use during pregnancy are discussed. Finally, possible interventions targeting the correlated risk factors and recommendations for clinical work are presented.

Prenatal drug exposure, behavioral problems, and drug experimentation among African-American urban adolescents

PURPOSE

To examine how prenatal drug exposure (PDE) to heroin/cocaine and behavioral problems relate to adolescent drug experimentation.

METHODS

The sample included African-American adolescents (mean age = 14.2 years, SD = 1.2) with PDE (n = 73) and a nonexposed community comparison (n = 61). PDE status was determined at delivery through toxicology analysis and maternal report. Internalizing/externalizing problems were assessed during adolescence with the Behavior Assessment System for Children, Second Edition. Drug experimentation was assessed by adolescent report and urine analysis. Logistic regression evaluated the likelihood of drug experimentation related to PDE and behavioral problems, adjusting for age, gender, PDE, perceived peer drug use, and caregiver drug use. Interaction terms examined gender modification.

RESULTS

Sixty-seven subjects (50%) used drugs: 25 (19%) used tobacco/alcohol only and 42 (31%) used marijuana/illegal drugs. Ninety-four subjects (70%) perceived peer drug use. PDE significantly increased the risk of tobacco/alcohol experimentation (odds ratio = 3.07, 95% confidence interval [CI] 1.09-8.66, p = .034) but not after covariate adjustment (adjusted odds ratio [aOR] = 1.16, 95% CI .31-4.33, p > .05). PDE was not related to the overall or marijuana/illegal drug experimentation. The likelihood of overall drug experimentation was doubled per SD increase in externalizing problems (aOR = 2.28, 95% CI 1.33-3.91, p = .003) and, among girls, 2.82 times greater (aOR = 2.82, 95% CI 1.34-5.94, p = .006) per SD increase in internalizing problems. Age and perceived peer drug use were significant covariates.

CONCLUSIONS

Drug experimentation was relatively common (50%), especially in the context of externalizing problems, internalizing problems (girls only), older age, and perceived peer drug use. Findings support the Problem Behavior Theory and suggest that adolescent drug prevention addresses behavioral problems and promotes prosocial peer groups.

Self-reported adolescent behavioral adjustment: effects of prenatal cocaine exposure

PURPOSE

To assess the direct effects of prenatal cocaine exposure (PCE) on adolescent internalizing, externalizing, and attention problems, controlling for confounding drug and environmental factors.

METHOD

At 12 and 15 years of age, 371 adolescents (189 PCE and 182 noncocaine exposed), primarily African-American and of low socioeconomic status, participating in a longitudinal, prospective study from birth were assessed for behavioral adjustment using the Youth Self-Report.

RESULTS

Longitudinal mixed model analyses indicated that PCE was associated with greater externalizing behavioral problems at ages 12 and 15 years and more attention problems at age 15, after controlling for confounders. PCE effects were not found for internalizing behaviors. PCE adolescents in adoptive/foster care reported more externalizing and attention problems than PCE adolescents in biological mother/relative care at age 12 or noncocaine-exposed adolescents at both ages. No PCE by gender interaction was found. Prenatal marijuana exposure, home environment, parental attachment and monitoring, family conflict, and violence exposure were also significant predictors of adolescent behavioral adjustment.

CONCLUSIONS

PCE is a risk factor for poor behavioral adjustment in adolescence.

Effects of prenatal cocaine exposure on child behavior and growth at 10 years of age

We examined physical growth and behavioral outcomes in 226 10-year-old children who were participants in a longitudinal study of prenatal cocaine exposure (PCE), while controlling for other factors that affect development. During the first trimester, 42% of the women used cocaine, with use declining across pregnancy. At the 10-year follow-up, the caregivers were 37years old, had 12.8years of education, and 50% were African American. First trimester cocaine exposure predicted decreased weight, height, and head circumference at 10years. First trimester cocaine use also predicted maternal ratings of less sociability on the EAS Temperament Survey and more withdrawn behavior problems on the Child Behavior Checklist, more anxious/depressed behaviors on the Teacher Report Form, and more self-reported depressive symptoms on the Children's Depression Inventory. In addition, exposure to violence mediated the effect of PCE on child and teacher reports of depressive symptoms, but not of maternal reports of sociability and withdrawn behaviors. These behaviors may be precursors of later psychiatric problems.

Developmental consequences of perinatal cannabis exposure: behavioral and neuroendocrine effects in adult rodents

RATIONALE

Cannabis is the most commonly used illicit drug among pregnant women. Since the endocannabinoid system plays a crucial role in brain development, maternal exposure to cannabis derivatives might result in long-lasting neurobehavioral abnormalities in the exposed offspring. It is difficult to detect these effects, and their underlying neurobiological mechanisms, in clinical cohorts, because of their intrinsic methodological and interpretative issues.

OBJECTIVES

The present paper reviews relevant rodent studies examining the long-term behavioral consequences of exposure to cannabinoid compounds during pregnancy and/or lactation.

RESULTS

Maternal exposure to even low doses of cannabinoid compounds results in atypical locomotor activity, cognitive impairments, altered emotional behavior, and enhanced sensitivity to drugs of abuse in the adult rodent offspring. Some of the observed behavioral abnormalities might be related to alterations in stress hormone levels induced by maternal cannabis exposure.

CONCLUSIONS

There is increasing evidence from animal studies showing that cannabinoid drugs are neuroteratogens which induce enduring neurobehavioral abnormalities in the exposed offspring. Several preclinical findings reviewed in this paper are in line with clinical studies reporting hyperactivity, cognitive impairments and altered emotionality in humans exposed in utero to cannabis. Conversely, genetic, environmental and social factors could also influence the neurobiological effects of early cannabis exposure in humans.

Prenatal drug exposure: infant and toddler outcomes

This manuscript provides an overview of the current scientific literature on the impact of maternal drug use, specifically opioids and cocaine, during pregnancy on the acute and long-term outcomes of infants and toddlers from birth through age 3 years. Emphasis with regard to opioids is placed on heroin and opioid substitutes used to treat opioid addiction, including methadone, which has long been regarded as the standard of care in pregnancy, and buprenorphine, which is increasingly being investigated and prescribed as an alternative to methadone. Controlled studies comparing methadone at high and low doses, as well as those comparing methadone with buprenorphine, are highlighted and the diagnosis and management of neonatal abstinence syndrome is discussed. Over the past two decades, attention of the scientific and lay communities has also been focused on the potential adverse effects of cocaine and crack cocaine, especially during the height of the cocaine epidemic in the United States. Herein, the findings are summarized from prospective studies comparing cocaine-exposed with non-cocaine-exposed infants and toddlers with respect to anthropometric growth, infant neurobehavior, visual and auditory function, and cognitive, motor, and language development. The potentially stigmatizing label of the so-called "crack baby" preceded the evidence now accumulating from well-designed prospective investigations that have revealed less severe sequelae in the majority of prenatally exposed infants than originally anticipated. In contrast to opioids, which may produce neonatal abstinence syndrome and infant neurobehavioral deficits, prenatal cocaine exposure appears to be associated with what has been described as statistically significant but subtle decrements in neurobehavioral, cognitive, and language function, especially when viewed in the context of other exposures and the caregiving environment which may mediate or moderate the effects. Whether these early findings may herald more significant learning and behavioral problems during school-age and adolescence when the child is inevitably confronted with increasing social and academic challenges is the subject of ongoing longitudinal research.

Moderate use of alcohol, tobacco and cannabis during pregnancy: new approaches and update on research findings

Interest in fetal origins of adverse offspring outcomes has grown extensively in the last decade. This has resulted in many published studies focusing on exposure in utero to substances and human offspring outcomes. Exposure to maternal substance use in pregnancy is believed to be a preventable hazard, and is therefore a main issue for public health concern and policy. However, an important question in human studies remains whether prenatal substance use exposure has an aetiological role in pathways to adverse developmental and behavioural outcomes via teratological effects. Recent insights and developments in research methodology will aid the adequate and more refined testing of associations between prenatal substance use and offspring outcomes. In particular, novel approaches could assist in disentangling the exposure to substance effects from correlated risk factors. The purpose of this manuscript is therefore to provide an overview of methodological issues involved in studies that focus on the association between maternal substance use during pregnancy and offspring's outcomes, to describe novel approaches to test these associations, and present some examples of new and well-designed studies and discuss their findings.

Executive functioning at ages 5 and 7 years in children with prenatal cocaine exposure

This prospective longitudinal study evaluated the effect of prenatal cocaine exposure (PCE) on executive functioning in 5- and 7-year-old children. In total, 154 pregnant cocaine users, identified by urine toxicology and structured interviews, were matched to 154 nonusers. Children were assessed by certified masked evaluators, and caregivers were interviewed by experienced staff during home visits. In approximately 90% of the surviving sample tested at ages 5 and 7 years, structural equation modeling demonstrated that an increased head circumference at birth (adjusted for gestation) significantly predicted better performance on executive functioning, and that PCE was indirectly related to executive functioning through its significant negative effect on head circumference at birth. At age 5 years, quality of environment also predicted executive functioning, and the R(2) for the total model was 0.24. At 7 years, caregiver functioning predicted quality of environment, which in turn was positively related to executive functioning, and girls had better executive functioning. The total model at age 7 years accounted for 30% of the variance in executive functioning.

Cannabis and the developing brain: insights from behavior

The isolation and identification, in 1964, of delta-9-tetrahydrocannabinol (THC), the primary psychoactive compound in cannabis, opened the door to a whole new field of medical research. The exploration of the therapeutic potential of THC and other natural and synthetic cannabinoid compounds was paralleled by the discovery of the endocannabinoid system, comprising cannabinoid receptors and their endogenous ligands, which offered exciting new insights into brain function. Besides its well-known involvement in specific brain functions, such as control of movement, memory and emotions, the endocannabinoid system plays an important role in fundamental developmental processes such as cell proliferation, migration and differentiation. For this reason, changes in its activity during stages of high neuronal plasticity, such as the perinatal and the adolescent period, can have long-lasting neurobehavioral consequences. Here, we summarize human and animal studies examining the behavioral and neurobiological effects of in utero and adolescent exposure to cannabis. Since cannabis preparations are widely used and abused by young people, including pregnant women, understanding how cannabinoid compounds affect the developing brain, leading to neurobehavioral alterations or neuropsychiatric disorders later in life, is a serious health issue. In addition, since the endocannabinoid system is emerging as a novel therapeutic target for the treatment of several neuropsychiatric diseases, a detailed investigation of possible adverse effects of cannabinoid compounds on the central nervous system (CNS) of immature individuals is warranted.

Effects of prenatal cocaine exposure on growth: a longitudinal analysis

OBJECTIVE

There has been a limited amount of research on the long-term effects of prenatal cocaine exposure on growth of the infant, and there has been no use of longitudinal growth models. We investigated the effects of prenatal cocaine exposure on offspring growth from 1 through 10 years of age by using a repeated-measures growth-curve model.

METHODS

Women were enrolled from a prenatal clinic and interviewed at the end of each trimester of pregnancy about their cocaine, crack, alcohol, marijuana, tobacco, and other drug use. Fifty percent of the women were white, and 50% were black. Follow-up assessments occurred at 1, 3, 7, and 10 years of age.

RESULTS

Cross-sectional analyses showed that children exposed to cocaine during the first trimester (n = 99) were smaller on all growth parameters at 7 and 10 years, but not at 1 or 3 years, than the children who were not exposed to cocaine during the first trimester (n = 125). The longitudinal analyses indicated that the growth curves for the 2 groups diverged over time: children who were prenatally exposed to cocaine grew at a slower rate than children who were not exposed. These analyses controlled for other factors associated with child growth.

CONCLUSIONS

To our knowledge, this is the first study of the long-term effects of prenatal cocaine exposure to conduct longitudinal growth-curve analyses using 4 time points in childhood. Children who were exposed to cocaine during the first trimester grew at a slower rate than those who were not exposed. These findings indicate that prenatal cocaine exposure has a lasting effect on child development.

Learning disabilities and intellectual functioning in school-aged children with prenatal cocaine exposure

Risk for developing a learning disability (LD) or impaired intellectual functioning by age 7 was assessed in full-term children with prenatal cocaine exposure drawn from a cohort of 476 children born full term and enrolled prospectively at birth. Intellectual functioning was assessed using the Wechsler Intelligence Scale for Children-Third Edition (Wechsler, 1991) short form, and academic functioning was assessed using the Wechsler Individual Achievement Test (WIAT; Wechsler, 1993) Screener by examiners blind to exposure status. LDs were categorized based on ability-achievement discrepancy scores, using the regression-based predicted achievement method described in the WIAT manual. The sample in this report included 409 children (212 cocaine-exposed, 197 non-cocaine-exposed) from the birth cohort with available data. Cumulative incidence proportions and relative risk values were estimated using STATA software (Statacorp, 2003). No differences were found in the estimate of relative risk for impaired intellectual functioning (IQ below 70) between children with and without prenatal cocaine exposure (estimated relative risk = .95; 95% confidence interval [CI] = 0.65, 1.39; p = .79). The cocaine-exposed children had 2.8 times greater risk of developing a LD by age 7 than non-cocaine-exposed children (95% CI = 1.05, 7.67; p = .038; IQ >/= 70 cutoff). Results remained stable with adjustment for multiple child and caregiver covariates, suggesting that children with prenatal cocaine exposure are at increased risk for developing a learning disability by age 7 when compared to their non-cocaine-exposed peers.

Is prenatal tobacco exposure a risk factor for early adolescent smoking? A follow-up study

Recent reports indicate a relation between prenatal tobacco exposure (PTE) and offspring smoking. Many of these reports have been retrospective or have not included important variables such as other prenatal substance exposures, maternal and child psycho-social characteristics, mother's current smoking, and friends' smoking. No prior study has examined the timing of PTE. In this prospective study of a birth cohort of 567 14-year-olds, we examined the relation between trimester-specific PTE, offspring smoking, and other correlates of adolescent smoking. Average age of the adolescents was 14.8 years (range: 13.9-16.6 years), 51% were female, 54% were African-American. Data on maternal tobacco and other substance use were collected both prenatally and postnatally, 51% of the mothers were prenatal smokers and 53% smoked when their children were 14 years. PTE in the third trimester significantly predicted offspring smoking (ever/never, smoking level, age of onset) when demographic and other prenatal substances were included in the analyses. PTE remained a significant predictor of the level of adolescent smoking when maternal and child psychological characteristics were added to the model. When more proximal measures of the child's smoking were included in the model, including mother's current smoking and friends' smoking, PTE was no longer significant. Significant predictors of adolescent smoking at age 14 were female gender, Caucasian race, child externalizing behavior, maternal anxiety, and child depressive symptoms. Although direct effects of PTE on offspring smoking behavior have previously been reported from this study and by others, by early-adolescence, this association is not significant after controlling for the more proximal covariates of adolescent smoking such as mother's current smoking and peer smoking.

An analysis of the effects of prenatal alcohol exposure on growth: A teratologic model

The association between prenatal exposure to alcohol and growth is linear, and effects have been measured at levels of exposure that are considerably below one drink per day. Thus, with respect to growth deficits, there is no safe level of drinking during pregnancy. Alcohol exposure during gestation causes growth deficits among the offspring at birth and during infancy. At older ages, however, growth deficits are reported in some, though not all, studies. Exposed offspring who grow up in more privileged environments are apparently able to make up their growth deficits, while those raised in less optimal circumstances do not. This means that there is an interaction between the environment in which a child is raised and the expression of the effects of prenatal alcohol exposure. The long-term implications of growth deficits are not yet well understood.

On the symmetry of limb deficiencies among children with multiple congenital anomalies

In humans, unpaired organs are placed in a highly ordered pattern along the left-right axis. As indicated by animal studies, a cascade of signaling molecules establish left-right asymmetry in the developing embryo. Some of the same genes are involved also in limb patterning. To provide a better insight into the connection between these processes in humans, we analysed the symmetry of limb deficiencies among infants with multiple congenital anomalies. The study was based on data collected by the International Clearinghouse for Birth Defects Monitoring Systems (ICBDMS). Registries of the ICBDMS provided information on infants who, in addition to a limb deficiency, also had at least one major congenital anomaly in other organ systems. We reviewed 815 such cases of which 149 cases (18.3 %) were syndromic and 666 (81.7 %) were nonsyndromic. The comparisons were made within the associated limb deficiencies, considering the information on symmetry, using a comparison group with malformations associated not involved in the index association. Among the non-syndromic cases, the left-right distribution of limb deficiencies did not differ appreciably between limb deficiency subtypes (e.g., preaxial, transverse, longitudinal). The left-right distribution of limb anomalies did not differ among most types of non-limb anomalies, though a predominance of left-sided limb deficiencies was observed in the presence of severe genital defects - odds ratio [OR], 2.6; 95 % CI, 1.1-6.4). Limb deficiencies (LDs) were more often unilateral than bilateral when accompanied by gastroschisis (OR, 0.1) or axial skeletal defects (OR, 0.5). On the contrary, LDs were more often bilateral than unilateral when associated with cleft lip with or without cleft palate (OR, 3.9) or micrognathia (OR, 2.6). Specifically, we found an association between bilateral preaxial deficiencies and cleft lip, bilateral amelia with gastroschisis and urinary tract anomalies, and bilateral transverse deficiencies and gastroschisis and axial skeleton defects. Of 149 syndromic cases, 62 (41.6 %) were diagnosed as trisomy 18. Out of the 30 cases of trisomy 18 with known laterality, 20 cases were bilateral. In the remainder the right and left sides were equally affected. Also, in most cases (74.4 %) only the upper limbs were involved. In conclusion the left-right distribution of limb deficiencies among some non-limb anomalies may suggest a relationship between the development of the limb and the left-right axis of the embryo.

Prenatal substance exposure: effects on attention and impulsivity of 6-year-olds

Attention and impulsivity of prenatally substance-exposed 6 year olds were assessed as part of a longitudinal study. Most of the women were light to moderate users of alcohol and marijuana who decreased their use after the first trimester of pregnancy. Tobacco was used by a majority of women and did not change during pregnancy. The women, recruited from a prenatal clinic, were of lower socio-economic status, and over half were African American. Attention and impulsivity were assessed using a Continuous Performance Task. Second and third trimester tobacco exposure and first trimester cocaine use predicted increased omission errors. Second trimester marijuana use predicted more commission errors and fewer omission errors. There were no significant effects of prenatal alcohol exposure. Lower Stanford-Binet Intelligence Scale composite scores, male gender, and an adult male in the household also predicted more errors of commission. Lower SBIS composite scores, younger child age, maternal work/ school status, and higher maternal hostility scores predicted more omission errors. These findings indicate that prenatal substance use has an effect on attentional processes.

Teratogenic actions of ethanol in the mouse: a minireview

The deleterious effects of prenatal ethanol exposure have been extensively documented in clinical and experimental studies. This paper provides an overview of work conducted with mice to examine the myriad of adverse consequences that result from embryonic/fetal exposure to ethanol. All of the hallmark features of the clinical fetal alcohol syndrome have been demonstrated in mice, including prenatal and postnatal growth retardation, structural malformations and behavioral abnormalities associated with central nervous system dysfunction. As expected, the severity and profile of effects is related to both dosage level and timing of exposure. In addition, these effects have been demonstrated following acute and chronic exposure, with a variety of routes of administration employed. Furthermore, a number of strains have been used in these studies and the variant response (susceptibility) to the teratogenic actions of ethanol exhibited among different mouse strains support the notion that genetic factors govern, at least in part, vulnerability to these effects of ethanol. More recent studies using mouse models have focused on examining potential mechanisms underlying the full spectrum of ethanol's teratogenic actions.

Prenatal alcohol exposure and academic achievement at age six: a nonlinear fit

This is a report on the effects of prenatal alcohol exposure on the academic achievement of children at 6 years of age. In this longitudinal study, women were interviewed at the end of each trimester of pregnancy, at delivery, and at 8, 18, 36, and 72 months postpartum. The women were of lower socioeconomic status, high school-educated, and moderate users of alcohol. The offspring received age-appropriate physical and developmental assessments at each follow-up. Linear regression and nonlinear curve fitting were used to investigate the nature and shape of the relationship between prenatal alcohol exposure and achievement. In addition, the role of child IQ in this relationship was explored. Alcohol exposure during the second trimester predicted deficits in each of the three subtests of the Wide Range Achievement Test-Revised (WRAT-R): reading, spelling, and arithmetic. The relationship was partially reduced by the addition of IQ to the model, but prenatal alcohol exposure still predicted significant deficits in achievement, even after controlling for IQ. Tests for the shape of the relationship demonstrated that the effect of prenatal exposure on the arithmetic subtest of the WRAT-R was a linear or dose-response relationship. By contrast, the relationships between prenatal alcohol exposure and performance on the spelling and reading subtests of the WRAT-R were better modeled as threshold effects. The thresholds for both were approximately 1 drink/day in the second trimester.

Effects of neonatal exposure to clonidine on basal and activated central noradrenaline metabolism and in vivo overflow

The occurrence of persistent effects of chronic neonatal exposure to the alpha 2-adrenoceptor agonist clonidine was investigated by determination of tissue concentrations of monoamines and metabolites and in vivo overflow of noradrenaline and its metabolites, in various rat brain regions during adulthood. Rat pups were treated with clonidine from postnatal day 10-20 and all measurements were carried out between postnatal day 40 and 58. Tissue concentrations of monoamines and metabolites of the early clonidine-treated rats did not differ significantly from the control group. A challenge with yohimbine did not reveal altered responses of monoaminergic systems, except for the failure of an increased serotonergic activity in the medulla pons. In vivo microdialysis measurements revealed an elevated basal extracellular noradrenaline level in amygdala, but not in frontal cortex and hippocampus. Pharmacological challenge in vivo with idazoxan did not reveal differences between clonidine- and saline-exposed rats. These results confirm previous findings that continuous activation of alpha 2-adrenoceptors during a particular period of rat brain development may result in long-lasting but small changes in monoaminergic activity. However, these alterations are not very consistent and may depend on the parameter chosen to reflect monoaminergic activity and are not revealed more clearly by activating (challenging) the noradrenaline system with alpha2-adrenoceptor antagonists.

Increased alpha 2-adrenoceptor mediated regulation of adult rat brain noradrenaline overflow after chronic neonatal exposure to propranolol; a microdialysis study

Direct and persistent effects of chronic neonatal administration of the beta-adrenoceptor antagonist propranolol on brain noradrenergic activity were investigated by measuring tissue concentrations of noradrenaline and its metabolites and in vivo overflow of noradrenaline during adulthood. Rat pups were chronically treated with propranolol from postnatal day 1 to day 10. Determination of monoamine metabolism after the last injection showed an increase in noradrenaline metabolism in frontal cortex, limbic system and hippocampus of propranolol-exposed rats, but 47 days after this last injection it was apparent that these effects were not long-lasting. Moreover, basal noradrenaline overflow in vivo in the hippocampus of 40-55 day-old propranolol-exposed rats did not differ from that in controls. However, the regulation of noradrenaline release seemed to have been altered, since a pharmacological challenge with the alpha 2-adrenoceptor antagonist idazoxan induced an enhanced increase in the in vivo noradrenaline overflow in propranolol-exposed rats compared to controls. It is suggested that the neonatal beta-blockade induced a supersensitivity of the presynaptic alpha 2-adrenoceptor. The precise mechanism underlying this effect has to be elucidated.

Prenatal methamphetamine attenuates serotonin mediated renin secretion in male and female rat progeny: evidence for selective long-term dysfunction of serotonin pathways in brain

In adult rats, methamphetamine produces biochemical alterations in brain serotonin (5-HT) neurons. Since 5-HT is critical to the development of fetal 5-HT neurons and target tissues, we hypothesized that in utero exposure to methamphetamine could result in long-term alterations in postnatal 5-HT systems. Pregnant Sprague-Dawley rats, administered either saline or (+/-)methamphetamine (5 mg/kg, s.c., b.i.d.) from gestational day 13 to 20, were divided into three treatment groups: Saline-injected/Ad Lib Fed (VEH); Saline-injected/Pair Fed (PF); and methamphetamine injected (METH). Prenatal methamphetamine exposure did not alter litter size, gender number, or progeny birth weights. Functional alterations in serotonergic systems were determined in postnatal day (PD) 70 male progeny and in PD 30 female progeny by measuring changes in 5-HT mediated increases in plasma hormones following a single injection of the 5-HT releaser p-chloroamphetamine (PCA; 8 mg/kg). Prenatal methamphetamine produced long-term marked (-30 to -62%) attenuation of plasma renin responses to PCA in male and female progeny. In contrast, no alterations were observed in the ACTH, corticosterone, or prolactin responses to PCA in male and female progeny. Prenatal methamphetamine did not alter basal levels of any hormones measured regardless of gender. No significant differences were observed in the density of cortical or hypothalamic 5-HT uptake sites, or in the density of cortical 5-HT1 or 5-HT2 receptors in male progeny. The lack of significant differences in cortical 5-HT uptake sites observed between PF and METH treated dams 2 days post-parturition indicates that methamphetamine was not neurotoxic to the pregnant dams. These data, which demonstrate longterm postnatal deficits in 5-HT mediated renin secretion, suggest selective functional alterations of brain 5-HT systems in male and female progeny exposed in utero to methamphetamine.