Maternal thyroid hormones play critical role in brain development of fetus. Low maternal iodine intake and thyroid autoimmunity may hamper this development due to lack of thyroid hormone production in such situations. Iodine deficiency is a worldwide problem and thyroid autoimmunity is emerging in countries where universal salt iodisation is being promoted. Pakistan is one of such countries where both problems are coexisting. This book contains findings of a longitudinal study conducted to evaluate the magnitude of iodine deficiency and thyroid autoimmunity in pregnant women residing in a metropolis city of Pakistan. A comprehensive background as well as review of this problem is also provided.These findings are useful for future planning of strategies to improve maternal and neonatal health in less developed countries.