Fish is generally considered an integral component of a healthy diet. However, it is a complex exposure. Fish is the primary dietary source of n-3 long-chain polyunsaturated fatty acids and a rich source of protein, selenium, iodine, and vitamin d but is also a major source of exposure to methylmercury and other environmental pollutants. In utero exposure to nutrients and toxicants found in the same fish might act on the exact same end points at an opposite direction. In the present chapter, we summarize findings from observational studies and randomized clinical trials on the association of fish consumption during pregnancy with fetal growth and preterm birth, childhood obesity, neurodevelopment, and allergic diseases. Overall, evidence on the association of maternal fish consumption during pregnancy with child health outcomes has been largely inconsistent. Further studies using biomarker information on both the amounts of fatty acids and environmental chemicals contained within fish are essential for refining estimates of the influence of prenatal fish intake on child growth and development.