Turunen S, Vääräsmäki M, Lahesmaa‐Korpinen AM, et al. - Given that maternal hyperthyroidism and antithyroid medications were correlated with adverse pregnancy and perinatal outcomes, researchers conducted this nationwide register‐based study to explore the relationship of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and included all singleton births in Finland between 2004 and 2013 (N = 571,785). A total of 2,144 (0.37%) of all the women had diagnoses of hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Maternal hyperthyroidism was linked to older age, multiparity, smoking, previous miscarriages, and overweight or obesity compared with the mothers without thyroid disease. In addition, the mothers diagnosed with hyperthyroidism had increased chances of gestational hypertensive disorders, cesarean sections, placental abruptions, preterm births, small‐for‐gestational‐age newborns, and neonatal intensive care unit treatment. 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.