Cohort Profile Update: 2015 Pelotas (Brazil) Birth Cohort Study－follow-ups from 2 to 6–7 years, with COVID-19 impact assessment

What is the reason for the new data collection?There were four main reasons to conduct new follow-ups at 2 years, 4 years, 5 years and 6-7 years: (i) to monitor lifecourse determinants of health as children moved into middle Key Features� The 2015 Pelotas Birth Cohort is a population-based study in Pelotas city, Brazil.It originally aimed to investigate life-course determinants of health and development, and investigate time trends comparing with earlier birth cohorts in the same city.The 4275 participants were assessed at birth and previously followed at ages 3 and 12 months.� Here we present details of new follow-ups at ages 2, 4 and 6-7 years, a COVID-19 impact study at age 5 years, and a nested randomized trial of two parenting programmes.� New areas of research include violence and psychosocial development, stress, sleep patterns and impacts of the COVID-19 pandemic.New biomarkers have been collected, including hair cortisol concentration and genetic data, and new detailed assessments of the caregiving environment and child development have been made in recent follow-ups.The nested PI � A trial evaluated effects of two group-based parent-training programmes on parenting and child development.� Follow-up rates were 95.4% (n ¼ 4014) at age 2 years, 95.4% (n ¼ 4010) at 4 years and 92.0%(n ¼ 3867) at 6-7 years.The web-based COVID-19 impact study included 2183 participants (56.6%).The PI � A trial of parenting programmes includes 369 mother-child dyads.