The aims of the BIBS Study The Brain Imaging in Babies study (BIBS) aims to improve understanding of how a baby's brain develops from before birth, up until 3-4 years of age. Working with children from a variety of backgrounds and communities, the investigators use a combination of state-of-the-art diagnostic tools such as MRI scans alongside traditional behavioural assessments to capture the earliest information on infant brain development. The focus of the BIBS study MRI scanning is a safe way of producing detailed images using strong magnetic fields and radio waves. It does not use X-ray. Along with learning more about brain development in general, the investigators also try to identify features that may in future help predict whether a child will or will not develop traits of conditions such as Autism Spectrum Disorder (ASD) or Attention Deficit Hyperactivity Disorder (ADHD). Long-term, this may help target useful interventions early on, helping children who are most in need. Since COVID-19 arrived in the United Kingdom (U.K.) in 2020, the investigators have been given ethical approval to include testing for this infection in the mothers and children participating in the study. This may provide an opportunity to better understand how mother and baby respond to infections. The investigators particularly welcome mothers who have had a positive COVID-19 test during their pregnancy to join the study.