Objective: The objective is to provide clinical guidelines for the management of thyroid problems present during pregnancy and in the postpartum.

Participants: The Chairman was selected by the Clinical Guidelines Committee of The Endocrine Society. The Chairman requested participation by the Latin American Thyroid Society, the Asia and Oceania Thyroid Society, the American Thyroid Association, the European Thyroid Association, and the American Association of Clinical Endocrinologists, and each organization appointed a member to the committee. Two members of The Endocrine Society were also asked to participate. The group worked on the guidelines for 2 yr and held two meetings. There was no corporate funding, and no members received remuneration.

Evidence: Applicable published and peer-reviewed literature of the last two decades was reviewed, with a concentration on original investigations. The grading of evidence was done using the United States Preventive Services Task Force system and, where possible, the GRADES system.

Consensus Process: Consensus was achieved through conference calls, two group meetings, and exchange of many drafts by E-mail. The manuscript was reviewed concurrently by the Clinical Guidelines Committee, members of The Endocrine Society, and members of each of the collaborating societies. Many valuable suggestions were received and incorporated into the final document. Each of the societies endorsed the guidelines.

Conclusions: Management of thyroid diseases during pregnancy requires special considerations because pregnancy induces major changes in thyroid function, and maternal thyroid disease can have adverse effects on the pregnancy and the fetus. Care requires coordination among several healthcare professionals. Avoiding maternal (and fetal) hypothyroidism is of major importance because of potential damage to fetal neural development, an increased incidence of miscarriage, and preterm delivery. Maternal hyperthyroidism and its treatment may be accompanied by coincident problems in fetal thyroid function. Autoimmune thyroid disease is associated with both increased rates of miscarriage, for which the appropriate medical response is uncertain at this time, and postpartum thyroiditis. Fine-needle aspiration cytology should be performed for dominant thyroid nodules discovered in pregnancy. Radioactive isotopes must be avoided during pregnancy and lactation. Universal screening of pregnant women for thyroid disease is not yet supported by adequate studies, but case finding targeted to specific groups of patients who are at increased risk is strongly supported.