Che WI, et al. - A population-based study was designed to investigate pregnancy outcomes among births to women with idiopathic inflammatory myopathy (IIM) in relation to the time of IIM diagnosis using population-based data. The Swedish nationwide registers were applied to distinguish all singleton births that occurred between 1973 and 2016 among women diagnosed with IIM between 1998 and 2016 and among women unexposed to IIM. Researchers divided births according to the IIM status of the mother at the time of delivery: post-IIM (n = 68), 1–3 years pre-IIM (n = 23), > 3 years pre-IIM (n = 710) and unexposed to IIM (n = 4,101). Multivariate regression models were applied to evaluate relative risks of adverse pregnancy outcomes in post-IIM births and pre-IIM births separately, in comparison with their son-IIM comparators. They found higher risks of caesarean section, preterm birth and low birth weight in women who gave birth after IIM diagnosis. These data further emphasise the significance of special care and close monitoring of women with IIM. In pre-IIM births, higher frequencies of caesarean section and instrumental delivery highlight the requirement for future study on the impact of subclinical features of IIM on pregnancy outcomes.