Prenatal disturbance alters the size of the corpus callosum in young monkeys

The importance of ‘awareness’ for understanding fetal pain

Our understanding of when the fetus can experience pain has been largely shaped by neuroanatomy. However, completion of the cortical nociceptive connections just after mid-gestation is only one part of the story. In addition to critically reviewing evidence for whether the fetus is ever awake or aware, and thus able to truly experience pain, we examine the role of endogenous neuro-inhibitors, such as adenosine and pregnanolone, produced within the feto-placental unit that contribute to fetal sleep states, and thus mediate suppression of fetal awareness. The uncritical view that the nature of presumed fetal pain perception can be assessed by reference to the prematurely born infant is challenged. Rigorously controlled studies of invasive procedures and analgesia in the fetus are required to clarify the impact of fetal nociception on postnatal pain sensitivity and neural development, and the potential benefits or harm of using analgesia in this unique setting.

Effects of psychologic stress on fetal development and pregnancy outcome

Data from animal studies show that maternal stress is associated with disturbances in pregnancy outcomes and offspring development and behavior, possibly as a result of permanent structural and functional changes termed "early-life programming." There is growing interest in whether similar relationships are present in humans. Here we review recent significant findings from the literature on the impact of prenatal psychologic stressors on pregnancy outcome and offspring development, with a particular focus on the developing brain. Relevant papers were searched using PubMed, and reference lists from obtained articles were checked. In humans, prenatal stress is associated with pregnancy complications, developmental, cognitive, and behavioral disorders, and possible onset of psychopathology in later life. In contrast to the available research done in animals, virtually nothing is known about the effects of prenatal stress on morphologic fetal brain development, and the mechanisms underlying subsequent associated behavioral changes.

RETRACTED: Maternal adversity, glucocorticoids and programming of neuroendocrine function and behaviour

The fetus may be exposed to increased endogenous glucocorticoid or synthetic glucocorticoid in late gestation. Approximately 7% of pregnant women in Europe and North America are treated with synthetic glucocorticoid to promote lung maturation in fetuses at risk of preterm delivery. Very little is known about the mechanisms by which synthetic glucocorticoid or prenatal stress influence neurodevelopment in the human, or whether specific time windows of increased sensitivity exist. Glucocorticoids are essential for many aspects of normal brain development, but exposure of the fetal brain to excess glucocorticoid can have life-long effects on neuroendocrine function and behaviour. Both endogenous glucocorticoid and synthetic glucocorticoid exposure have a number of rapid effects in the fetal brain, including modification of neurotransmitter systems and transcriptional machinery. Such fetal exposure permanently alters hypothalamo-pituitary-adrenal (HPA) function in prepubertal, postpubertal and aging offspring, in a sex-dependent manner. Prenatal glucocorticoid manipulation also leads to modification of behaviour, brain and organ morphology, as well as altered regulation of other endocrine systems. Permanent changes in endocrine function will impact on health, since elevated cumulative exposure to endogenous glucocorticoid is linked to the premature onset of pathologies associated with aging.

The effects of prenatal maternal stress on children's cognitive development: Project Ice Storm

There exists considerable research on the effects of prenatal maternal stress on offspring. Animal studies, using random assignment to experimental and control groups, demonstrate the noxious effects of prenatal maternal stress on physical, behavioural and cognitive development. The generalizability of these results to humans is problematic given that cognitive attributions moderate reactions to stressors. In humans, researchers have relied upon maternal anxiety or exposure to life events as proxies for the stressors used with animals. Yet, the associations between maternal anxiety or potentially non-independent life events and problems in infants are confounded by genetic transmission of temperament from mother to child. We summarize the literature on prenatal maternal stress and infant cognitive development, leading to the conclusion that the human literature lacks the ability to separate the effects of the objective exposure to a stressor and the mother's subjective reaction. We then describe our prospective Project Ice Storm in which we are following 150 children who were exposed in utero to a natural disaster. We demonstrate significant effects of the objective severity of exposure on cognitive and language development at age two years with important moderating effects of the timing during pregnancy. The implications of our findings are discussed.

Are maternal smoking and stress during pregnancy related to ADHD symptoms in children?

BACKGROUND

There are some indications that maternal lifestyle during pregnancy (smoking and stress) contributes to symptoms of ADHD in children. We prospectively studied whether prenatal exposure to maternal smoking and/or stress is associated with ADHD symptoms and diagnostic criteria (according to DSM-IV) in 7-year-olds.

METHODS

Nulliparous Scandinavian women were consecutively recruited at their first prenatal health care visit and assessments of smoking and stress were collected at gestational weeks 10, 12, 20, 28, 32, and 36. Children were followed up at 7 years old. We obtained full data for 72% of the sample: ADHD symptoms were rated by 74% of mothers (n=290) and 96% of eligible teachers (n=208). Attrition analyses showed no differences on key variables between participants and non-participants at follow-up.

RESULTS

Results of multiple regression analyses showed prenatal exposure to smoking (beta=.16, p<.01) and stress (beta=.18, p<.01) were independently associated with later symptoms of ADHD. Results of logistic regression analyses showed that fulfillment of the diagnostic criteria for ADHD was related to exposure to prenatal stress (beta=.68, p<.01) especially in boys. The results were not confounded by sociodemographic factors or birth outcomes.

CONCLUSIONS

This study provides evidence that prenatal exposure to stress and smoking is independently associated with later symptoms of ADHD in human children, particularly for boys. Because stress and smoking are relatively common during pregnancy, and yet preventable, these results are of public health significance.

Prenatal origins of individual variation in behavior and immunity

The in utero environment plays a critical role in initiating the normal ontogeny of many physiological systems. As a consequence, disturbances during prenatal life can affect the baby's maturational trajectory and sometimes cause chronic alterations that influence health postpartum. Our review summarizes a series of studies in rhesus monkeys supporting these conclusions. Psychological disturbance or pharmacological stimulation of the gravid female's pituitary-adrenal axis affected the infant's neurological development: monkeys evinced immature neuromotor reflexes at birth, greater emotionality during the first year of life, and a smaller hippocampus as juveniles. Immune responses of the infants were also affected: lymphocyte proliferation, natural killer activity and cytokine production were reduced. Several mediating pathways were implicated, including the placental transfer of hormones and nutrients, and a differential response of the infant monkey to the rearing environment. For example, the establishment of beneficial types of microflora in the gastrointestinal tract was significantly reduced, which was associated with a greater risk for enteric infection. These findings indicate that events during fetal life can persistently influence physiology after birth and tilt the balance away from health and toward illness.

Reduced area of the corpus callosum in posttraumatic stress disorder

Magnetic resonance imaging (MRI) studies have revealed decreases in the mid-sagittal area of the corpus callosum (CC) in pediatric posttraumatic stress disorder (PTSD), but at present no data are available in adult PTSD patients. We have previously reported decreased whole-brain white matter (WM) volume in adults with PTSD and now report corpus callosum area from the same sample. MRI was used to obtain whole-brain images in 12 adult patients with PTSD and 10 matched controls. Total parenchyma (white matter plus gray matter [GM]) volume, mid-sagittal area of the CC and seven sub-regions of this structure were calculated. In PTSD patients, the total CC area, absolute and normalized to total brain parenchyma, was smaller compared with control values. Several absolute and normalized CC sub-regions were also smaller in PTSD patients: genu (region 2), mid-body (region 5) and isthmus (region 6). There was also a trend for the anterior mid-body (area 4) to be smaller in PTSD patients. No differences were found in the rostrum (region 1), rostral body (region 3) or splenium (region 7). Adult patients with PTSD had decreased CC area after correcting for total brain tissue, indicating that these differences are not attributable to generalized white matter atrophy. These findings are similar to previous results in children with PTSD and suggest specific changes in the CC.

Prenatal stress diminishes neurogenesis in the dentate gyrus of juvenile rhesus monkeys

BACKGROUND

Early life stress, including during fetal development, has been hypothesized to predispose individuals to several illnesses and psychiatric disorders later in adulthood.

METHODS

To determine whether prenatal stress alters neural, hormonal, and behavioral processes in nonhuman primates, pregnant rhesus monkeys were acutely stressed on a daily basis for 25% of their 24-week gestation with an acoustical startle protocol. At 2 to 3 years of age, hippocampal volume, neurogenesis in the dentate gyrus, and cortisol levels were evaluated in the offspring generated from stressed and control pregnancies.

RESULTS

Prenatal stress, both early and late in pregnancy, resulted in a reduced hippocampal volume and an inhibition of neurogenesis in the dentate gyrus. These changes were associated with increased pituitary-adrenal activity, as reflected by higher cortisol levels after a dexamethasone suppression test, and also with behavioral profiles indicative of greater emotionality.

CONCLUSIONS

These findings indicate that the prenatal environment can alter behavior, dysregulate neuroendocrine systems, and affect the hippocampal structure of primates in a persistent manner.