Turunen S, Vääräsmäki M, Lahesmaa‐Korpinen AM, et al. - In this nationwide register‐based study, researchers sought to explore the correlation of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and involved all singleton births in Finland between 2004 and 2013 (N = 571,785). Hyperthyroid mothers have been identified in the Medical Birth Register, and data on ATD use before and/or during pregnancy have been obtained from the Prescription Register. A total of 2,144 (0.37%) of all the women were diagnosed with hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Maternal hyperthyroidism was related to older age, multiparity, smoking, previous miscarriages, and overweight or obesity vs mothers without thyroid disease. Also, the mothers diagnosed with hyperthyroidism had increased chances of gestational hypertensive disorders, caesarean sections, placental abruptions, preterm births, small‐for‐gestational‐age newborns and neonatal intensive care unit treatment. The chances of pregnancy and/or perinatal complications were higher for those who had used ATDs (active disease indication), but those who had not received ATD treatment still had increased risks of these complications relative to non-thyroid disease mothers. Women with active hyperthyroidism and those with hyperthyroidism history should be considered at risk of developing pregnancy and perinatal complications and should be monitored during pregnancy.