['This longitudinal study aimed to investigate the prevalence of teething-related pain and fever and the early-life factors that may affect the risk of experiencing these disturbances within the first 1.5\xa0years of life.', 'Participants were recruited (n\xa0=\xa01033) through the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort (n\xa0=\xa01237). Interviews were performed tri-monthly regarding the prevalence of teething pain and fever in children from 6 to 18\xa0months of age. Crude and multivariable analyses were conducted using Poisson-log regression models.', 'Prevalence rates for teething pain and fever were 35.5 and 49.9\xa0% respectively. Multivariable Poisson regression analysis showed maternal second-hand tobacco smoke (SHS) exposure to increase the risk of both pain (mean ratio\xa0=\xa01.35; p\xa0=\xa00.006) and fever (mean ratio\xa0=\xa01.22; p\xa0=\xa00.025), whereas SHS exposure plus active smoking further increased risk of teething pain in the children (mean ratio\xa0=\xa01.89; p\xa0=\xa00.029). Delivery via Caesarean section increased risk of teething pain (mean ratio\xa0=\xa01.27; p\xa0=\xa00.033), while prenatal plasma vitamin D insufficiency lowered such a risk (mean ratio\xa0=\xa00.62; p\xa0=\xa00.012). Compared to Chinese infants, Indian babies exhibited lower risk of teething pain and fever (both p\xa0≤\xa00.001).'] Do early-life factors affect risk of pain and fever in infants during teething periods?