The focus of this paper is on the earliest stages of child development, the period from conception to the end of the child’s second year. This period has become known as the first 1000 days, a catchphrase that has become the rallying point for a number of Australian and international initiatives. While some of these have a general focus, such as the work of a cross-parliamentary group in the UK Parliament (Leadsom, Field, Burstow & Lucas, 2013; WAVE Trust, 2013, 2015), others are more narrowly focused on issues such as nutrition (Save the Children, 2012; Thousand Days, 2016) or on specific populations such as Aboriginal children (Arabena, Howell- Muers, Ritte, & Munro-Harrison, 2015; Arabena, Ritte & Panozzo, 2016).
The reason for focusing on this specific period is the growing body of evidence which shows that experiences during this period can have life-long consequences for health and wellbeing. Thus, as noted in the report of the World Health Organisation’s Commission on Social Determinants of Health (2008), Many challenges in adult society have their roots in the early years of life, including major public health problems such as obesity, heart disease, and mental health problems. Experiences in early childhood are also related to criminality, problems in literacy and numeracy, and economic participation. This paper seeks to summarise what is known about the biological processes and environmental characteristics that shape development during the first 1000 days, and what impact these have over the life span.
While there have already been many reviews of the literature on early development, all concluding that this period of life is critical in shaping health and wellbeing over the life course, there are several reasons why a new review of the evidence is needed, and why this paper differs from previous reviews. First, research in this area is rapidly advancing, and our understanding of the specific mechanisms that impact upon development is becoming more and more detailed and nuanced. Keeping up with the exponential growth in research is an ongoing challenge, and regular updates such as this one are needed.
Second, the new research has revealed whole aspects of biological functioning that were not previously recognised as playing a role in development, such as telomere effects and the role of the microbiome. This review is the most comprehensive attempt yet to incorporate all known sources of influence on development, and even those well read in this area will learn from the paper.
Third, the focus of the paper is on the first 1000 days, rather than the early years in general as in most previous reviews. This is on the grounds that the first 1000 days is the period of maximum developmental plasticity, and therefore the period with the greatest potential to affect health and wellbeing over the life course.