 This is a model community-based trial in Rhode Island RI, aimed at avoiding or minimizing morbidity from overt maternal hypothyroidism by systematic detection and treatment, beginning at the 1st prenatal visit. This model can be superimposed on existing prenatal screening programs and is intended ultimately to replace case-finding, which has recently been shown ineffective. Three aspects of maternal and child health are compromised when a pregnant woman is thyroid deficient: 1 the womans own health and well-being; 2 her babys brain development; and 3 overall health of the pregnancy e.g., fetal death, prematurity, preeclampsia. Thyroid stimulating hormone TSH measurement, a well accepted indicator of thyroid dysfunction, will serve as the primary test for both diagnosis and monitoring. A TSH value 10 mUL indicates overt hypothyroidism. Among the states 14,000 annual pregnancies, 42 women 0.3 will be overtly hypothyroid early in gestation 32 undiagnosed, and 10 under-treated. TSH values between 4.5 mUL 98th centile and 9.9 mUL indicate subclinical hypothyroidism. The 240 women in this category will also receive treatment, and information will be gathered about disease progression to inform future practice. Approximately half of all RIs pregnancies are cared for by practices in Greater Providence, and TSH testing will initially be introduced, there. The research component is also within that area. Testing will subsequently be extended to the entire state. The program is centrally managed by three units at Women and Infants Hospital, in consultation with RIs Birth Defects Program Director. Program goals are to: provide TSH testing to at least 70 of pregnant women in Greater Providence; provide TSH testing to at least 50 of pregnant women elsewhere in RI; test 70 of screened women by 12 weeks gestation, and 90 by 18 weeks gestation; begin treatment in Greater Providence by 13 weeks in 70, and by 19 weeks in 90; document successful treatment during pregnancy in 90 TSH 0.1 mUL and 2.0 mUL; retain 95 treated women to end of pregnancy, and 90 for up to 1 year postpartum; obtain pregnancy complications and birth outcomes for the entire cohort Vital Records. 