Growth restriction alters adult spatial memory and sensorimotor gating in a sex-specific manner

The persistent effects of foetal growth on child and adolescent mental health: longitudinal evidence from a large population-based cohort

Low birth weight for one's gestational age is associated with higher rates of child psychopathology, however, most studies assess psychopathology cross-sectionally. The effect of such foetal growth restriction appears to be strongest for attention problems in childhood, although adult studies have found associations with a range of outcomes, from depression to psychosis. We explore how associations between foetal growth and psychopathology change across age, and whether they vary by sex. We used a large nationally representative cohort of children from Ireland (N ~ 8000). Parents completed the Strengths and Difficulties Questionnaire (SDQ) at 3 time points (age 9, 13 and 17). Outcomes included a total problems scale and subscales measuring attention/hyperactivity, peer, conduct and emotional problems. Foetal growth had significant associations with all problem scales, even after controlling for sex, socioeconomic factors and parental mental health. The magnitude of these effects was small but relatively stable across ages 9-17. In males, foetal growth had the strongest associations with attention/hyperactivity and peer problems, whereas females showed more widespread associations with all four subscales. There was a trend for the association between foetal growth and emotional problems to increase with advancing age, approaching the borderline-abnormal threshold by age 17. Reduced foetal growth predicted persistently higher scores on all measured aspects of child and adolescent psychopathology. Associations with child attention/hyperactivity may generalize to a wider array of adult psychopathologies via adolescent-onset emotional problems. Future studies should explore potential age-dependent effects of foetal growth into the early 20s.

Explaining the Association Between Fetal Growth and Childhood ADHD Symptoms: Cross-cohort Replication

The association between restricted fetal growth and symptoms of attention deficit/hyperactivity disorder (ADHD) in childhood is well-replicated and robust. However, fetal growth is determined by many prenatal factors and associations with mental health may be confounded by familial and social context. In this study, we sought to quantify the relative contributions of prenatal factors and familial confounds to the association between fetal growth and ADHD symptoms. Two independent cohorts were analyzed, the Adolescent Brain Cognitive Development study (ABCD; United States) and the Growing Up in Ireland (GUI) study. ADHD symptoms were measured by the Child Behavior Checklist (ABCD) and the Strengths & Difficulties questionnaire (GUI) at age 9-10. Using sequential regression models, we assessed the change-in-association between fetal growth and ADHD symptoms after controlling for sex, familial factors (socioeconomic/demographic factors & family psychiatric history) and prenatal factors (pregnancy complications & maternal substance-use during pregnancy). Converging findings from cohorts suggested that over a quarter of the association between fetal growth and ADHD symptoms is attributable to familial confounds. The degree to which the association was explained by prenatal factors differed by cohort-pregnancy complications explained a larger proportion of the effect in ABCD (7.9%) than GUI (2.7%), and maternal substance-use explained a larger proportion of the effect in GUI (22.7%) compared to ABCD (4.8%). Different explanations of the fetal growth-ADHD association across cohorts suggests cohort-specific, and potentially nationally-specific, risk factors for fetal growth and related neurodevelopmental outcomes. The evidence suggests early prevention of ADHD in Ireland should focus on minimizing maternal smoking during pregnancy. In the US, prevention and treatment of pregnancy complications are highlighted as viable targets for intervention.

Hippocampal neurogenesis and memory in adolescence following intrauterine growth restriction

Intrauterine growth restriction (IUGR) is associated with hippocampal alterations that can increase the risk of short-term memory impairments later in life. Despite the role of hippocampal neurogenesis in learning and memory, research into the long-lasting impact of IUGR on these processes is limited. We aimed to determine the effects of IUGR on neuronal proliferation, differentiation and morphology, and on memory function at adolescent equivalent age. At embryonic day (E) 18 (term ∼E22), placental insufficiency was induced in pregnant Wistar rats via bilateral uterine vessel ligation to generate IUGR offspring (n = 10); control offspring (n = 11) were generated via sham surgery. From postnatal day (P) 36-44, spontaneous location recognition (SLR), novel object location and recognition (NOL, NOR), and open field tests were performed. Brains were collected at P45 to assess neurogenesis (immunohistochemistry), dendritic morphology (Golgi staining), and brain-derived neurotrophic factor expression (BDNF; Western blot analysis). In IUGR versus control rats there was no difference in object preference in the NOL or NOR, the similar and dissimilar condition of the SLR task, or in locomotion and anxiety-like behavior in the open field. There was a significant increase in the linear density of immature neurons (DCX+) in the subgranular zone (SGZ) of the dentate gyrus (DG), but no difference in the linear density of proliferating cells (Ki67+) in the SGZ, nor in areal density of mature neurons (NeuN+) or microglia (Iba-1+) in the DG in IUGR rats compared to controls. Dendritic morphology of dentate granule cells did not differ between groups. Protein expression of the BDNF precursor (pro-BDNF), but not mature BDNF, was increased in the hippocampus of IUGR compared with control rats. These findings highlight that while the long-lasting prenatal hypoxic environment may impact brain development, it may not impact hippocampal-dependent learning and memory in adolescence.

Models of Intrauterine growth restriction and fetal programming in rabbits

Intrauterine growth restriction (IUGR) affects approximately 10% of human pregnancies globally and has immediate and life-long consequences for offspring health. However, the mechanisms underlying the pathogenesis of IUGR and its association with later health and disease outcomes are poorly understood. To address these knowledge gaps, the use of experimental animals is critically important. Since the 50's different environmental, pharmacological, and surgical manipulations have been performed in the rabbit to improve our knowledge of the control of fetal growth, fetal responses to IUGR, and mechanisms by which offspring may be programmed by an adverse gestational environment. The purpose of this review is therefore to summarize the utility of the rabbit as a model for IUGR research. It first summarizes the knowledge of prenatal and postnatal development in the rabbit and how these events relate to developmental milestones in humans. It then describes the methods used to induce IUGR in rabbits and the knowledge gained about the mechanisms determining prenatal and postnatal outcomes of the offspring. Finally, it discusses the application of state of the art approaches in the rabbit, including high-resolution ultrasound, magnetic resonance imaging, and gene targeting, to gain a deeper integrative understanding of the physiological and molecular events governing the development of IUGR. Overall, we hope to engage and inspire investigators to employ the rabbit as a model organism when studying pregnancy physiology so that we may advance our understanding of mechanisms underlying IUGR and its consequences in humans and other mammalian species.

Blocked, delayed, or obstructed: What causes poor white matter development in intrauterine growth restricted infants?

Poor white matter development in intrauterine growth restricted (IUGR) babies remains a major, untreated problem in neonatology. New therapies, guided by an understanding of the mechanisms that underlie normal and abnormal oligodendrocyte development and myelin formation, are required. Much of our knowledge of the mechanisms that underlie impaired myelination come from studies in adult demyelinating disease, preterm brain injury, or experimental models of hypoxia-ischemia. However, relatively less is known for IUGR which is surprising because IUGR is a leading cause of perinatal mortality and morbidity, second only to premature birth. IUGR is also a significant risk factor for the later development of cerebral palsy, and is a greater risk compared to some of the more traditionally researched antecedents - asphyxia and inflammation. Recent evidence suggests that the white matter injury and reduced myelination in the brains of some preterm babies is due to impaired maturation of oligodendrocytes thereby resulting in the reduced capacity to synthesize myelin. Therefore, it is not surprising that the hypomyelination observable in the central nervous system of IUGR infants has similarly lead to investigations identifying a delay or blockade in the progress of maturation of oligodendrocytes in these infants. This review will discuss current ideas thought to account for the poor myelination often present in the neonate's brain following IUGR, and discuss novel interventions that are promising as treatments that promote oligodendrocyte maturation, and thereby repair the myelination deficits that otherwise persist into infancy and childhood and lead to neurodevelopmental abnormalities.

The Programming Power of the Placenta

Size at birth is a critical determinant of life expectancy, and is dependent primarily on the placental supply of nutrients. However, the placenta is not just a passive organ for the materno-fetal transfer of nutrients and oxygen. Studies show that the placenta can adapt morphologically and functionally to optimize substrate supply, and thus fetal growth, under adverse intrauterine conditions. These adaptations help meet the fetal drive for growth, and their effectiveness will determine the amount and relative proportions of specific metabolic substrates supplied to the fetus at different stages of development. This flow of nutrients will ultimately program physiological systems at the gene, cell, tissue, organ, and system levels, and inadequacies can cause permanent structural and functional changes that lead to overt disease, particularly with increasing age. This review examines the environmental regulation of the placental phenotype with particular emphasis on the impact of maternal nutritional challenges and oxygen scarcity in mice, rats and guinea pigs. It also focuses on the effects of such conditions on fetal growth and the developmental programming of disease postnatally. A challenge for future research is to link placental structure and function with clinical phenotypes in the offspring.

Neurodevelopment in children with intrauterine growth restriction: adverse effects and interventions

Intrauterine growth restriction (IUGR) is associated with higher rates of fetal, perinatal, and neonatal morbidity and mortality. The consequences of IUGR include short-term metabolic, hematological and thermal disturbances that lead to metabolic syndrome in children and adults. Additionally, IUGR severely affects short- and long-term fetal brain development and brain function (including motor, cognitive and executive function) and neurobehavior, especially neuropsychology. This review details the adverse effects of IUGR on fetal brain development and discusses intervention strategies.