Whilst preterm birth represents the single largest factor worldwide in terms of infant mortality [1], mortality rates associated with preterm birth have decreased in recent decades thanks to advances in perinatal and neonatal care [2, 3]. However, the improved survival of very preterm and very low birth weight infants has been associated with an increase in the prevalence of neonatal problems (including periventricular hemorrhage, chronic lung disease, retinopathy of prematurity (ROP), and septicemia) and neurodevelopmental sequelae [4]. Therefore, attention has increasingly focused on the quality of life of survivors, who are at greater risk of brain damage and consequent neurological disorders, and neuropsychological and behavioral impairments in childhood and later in life [5–8].

In this volume, leading experts from multiple disciplines, investigating various aspects of the long-term consequences of very preterm birth, have presented a comprehensive and updated summary of research in their field. As well as extending existing knowledge of the neurodevelopmental sequelae following very preterm birth, a shared aim of this burgeoning body of research is to identify the mechanisms underlying variations in outcome and thus recognize subgroups of children who are at increased risk of neurodevelopmental problems, who can then be referred early to appropriate intervention services.

Preterm birth occurs in a substantial percentage of the population: just less than 13% of US live births are reported as being preterm (< 37 completed weeks of gestation). Very preterm births, occurring before 32 completed gestational weeks, account for about 15% of preterm births, which is equivalent to 1–2% of all pregnancies [9].

Intrauterine and neonatal factors seem to be important in the pathogenesis of childhood and adolescent psychiatric disorders like infantile autism, attention deficit hyperactivity disorder (ADHD), and anorexia nervosa, but also in psychiatric disorders which are not usually seen until late adolescence or adulthood, such as schizophrenia. Being born preterm, with a low birth weight or with indications of fetal growth retardation are among the most robust and replicated perinatal risk factors associated with psychiatric outcome. Additionally, preterm delivery is more common in mothers with schizophrenia, mothers with bipolar disorder, and among women with postpartum psychoses. No consensus has yet been reached concerning the interpretation of the association between preterm birth and psychopathology. In this chapter we report some of the findings and methodological challenges in the field.

Introduction

In studies of preterm birth as a risk factor for development of psychiatric disorders in adulthood, at least four research traditions and paradigms can be identified.

Firstly, during the last 30 years, the evolution of neonatal intensive care has encouraged extensive follow- up studies of very low birth weight (VLBW; < 1500 g) and very preterm infants, investigating developmental, behavioral, and neurological outcome in early childhood (reviewed in Chapters 3, 9, and 11). This has partly occurred due to an increase in survival of very preterm and VLBW babies, the introduction of new medical technology, and improvements in clinical neonatal intensive care (see also Chapters 1 and 2). Consequently, longer periods of follow-up have been facilitated, as has the investigation of diverse cognitive and behavioral deficits in late childhood and early adolescence.

Introduction

As has been demonstrated elsewhere in this volume, preterm birth and/or low birth weight is common, possibly increasing and associated with adverse consequences [1]. Magnetic resonance imaging (MRI) studies in childhood have done an excellent job of relating the cognitive, behavioral, and academic problems faced by preterm and low birth weight individuals to underlying alterations of brain structure, as described in Chapter 5. However, a largely unanswered question is what happens to these individuals, and to their brains, as they grow up. This lack of information is not because preterm researchers have been idle, of course, but rather because the phenomenon of widespread survival after short gestation is historically quite recent. As cohorts of prematurely born people are now becoming adults, there is now a pressing need to determine their adult outcomes. Do impairments become attenuated, persist, or worsen? How are the usual processes of development and maturation altered by preexisting structural brain abnormalities? Is neural plasticity part of the problem, as well as a potential solution? What happens to the ageing preterm brain? Many of these questions are yet to be addressed, but in this chapter we will describe some imaging studies that are starting to bridge the gap between adolescence and adulthood. In this, we will be helped considerably by recent studies which have used MRI techniques to investigate normal adolescent brain development, and which will give us a baseline for understanding changes in the preterm brain.

At a time of exciting advances in neonatal intensive care and neuroimaging methods, when surviving preterm children represent an increasing percentage of the population, we conceived the current volume to provide the first single-source reference on the latest findings from research into the neurodevelopmental outcome following preterm birth.

New knowledge about the long-term cognitive, neurosensory, neurobiological, social, and behavioral correlates of preterm birth has emerged in the past decade mainly from two sources. Firstly, from “historical” studies of the initial preterm survivors who were examined from birth and have now reached adulthood. Secondly, from more recent studies using sophisticated neurodevelopmental assessments of the preterm infant at term, including neonatal magnetic resonance imaging techniques, which may potentially be used to identify the mechanisms underlying variations in outcome later in life; this may enable subgroups of individuals who are at increased risk of neurodevelopmental problems to benefit from appropriate intervention strategies which may be devised.

In this volume, many of the most admired and prolific investigators in different areas of preterm research present a comprehensive and up-to-date perspective on their work and areas of expertise, including directions for the future. We have been extremely fortunate to secure contributions from these researchers who have been instrumental in increasing the existing knowledge of the neurodevelopmental sequelae of preterm birth.

The volume is divided into six sections. The first introductory section presents an overview of the epidemiology of preterm birth and associated environmental and biological risk factors (Chapter 1).