 The subjects will be 176 pregnant women and adolescents discovered to have varying degrees of hypothyroidism during the first and early second trimesters. This disorder will be identified by a blood test offered as part of routine prenatal care in a CDC-sponsored community-based program at prenatal practices in Providence, Rhode Island. These 176 women all will receive appropriate treatment for their hypothyroidism, and permission will be sought to record information about the natural history of their condition during the first postpartum year, as a way to inform future practice. The women will range in age from about 17 to 44 years. Their racialethnic composition will reflect that of the general population of Rhode Island. 