The authors review the published data on thyroid pathology and pregnancy. Attention is focused in particular on alterations in thyroid function and the iodine metabolism during pregnancy, thyroid interactions between the fetus, the placenta and the maternal organism, the control of fetal thyroid hormonal production, thyroid hormones and fetal development, endemic goitre and pregnancy, endemic cretinism, hypothyroidism in pregnancy, mixematous coma, hyperthyroidism in pregnancy, thyroid cancer in pregnancy and perinatal thyroid disease (hypothyroidism and hyperthyroidism).