THYROID: Edited by Lewis E. Braverman and Angela M. LeungRisk of embryopathies with use of antithyroidal medicationsAndersen, Stine L.a,bAuthor Information aDepartment of Endocrinology bDepartment of Clinical Biochemistry, Aalborg University Hospital, Aalborg, Denmark Correspondence to Stine L. Andersen, MD, PhD, Department of Endocrinology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark; Department of Clinical Biochemistry, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark. Tel: +45 97 66 48 73; e-mail: firstname.lastname@example.org Current Opinion in Endocrinology & Diabetes and Obesity: October 2017 - Volume 24 - Issue 5 - p 364-371 doi: 10.1097/MED.0000000000000353 Buy Metrics Abstract Purpose of review Hyperthyroidism in pregnant women should be adequately treated to prevent maternal and fetal complications. The treatment of choice in pregnancy is antithyroidal medications (ATDs). The risk of embryopathies associated with the use of Methimazole (MMI) and Propylthiouracil (PTU) in early pregnancy is a matter of clinical attention and concern. This review describes current evidence and how scientific findings are reflected in current clinical guidelines. Recent findings Embryopathies after the use of ATDs were previously mainly described in case reports and considered rare. Recent large observational studies, including nonexposed control groups, have quantified an increased risk of embryopathies associated with use of ATDs during pregnancy. Findings suggest a risk of embryopathies with the use of both MMI and PTU, but the pattern of embryopathies differs, and embryopathies with the use of PTU appear less severe. Summary Current guidelines highlight the need for clinical attention on the use of ATDs in early pregnancy. Patients managed on ATDs for the treatment of hyperthyroidism should be counseled to report a pregnancy as early as possible. PTU is the recommended treatment in early pregnancy, but if the risk of relapse or worsening of hyperthyroidism is considered low, it is suggested that ATD treatment can be withdrawn followed by frequent monitoring of thyroid function. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.