Attainment of peak healthy lung function during the 18-26 yr window is a strong determinant of the rate of lung function decline during the later years of life. The attainment of a healthy peak lung function is mediated by pre and peri natal exposures ( in utero environment and nutrition) and exposure to environmental toxicants and nutrition during childhood and early adulthood. Towards this Indian birth cohorts, having collected comprehensive data on maternal nutrition and anthropometry can provide invaluable insight into the factors affecting lung function growth and their effect sizes in the Indian population. Therefore, in this observational study, the Investigator will be collecting data on lung function, current nutritional and environmental exposures and linking it to pre and peri natal data of the same participants in order to understand lung function growth and the reasons for an early decline in the Indian population, using a life course approach.