Fish is a good source of important nutrients which are related to nutritional benefits. Fish is a predominant source of polyunsaturated fatty acids and is low in saturated fatty acids. It is well-known that omega-3 fatty acids appear to confer multiple human health benefit like reduction of depressive symptoms. Accumulating evidence suggest an association between a low omega-3 fatty acids status after pregnancy and the occurrence of postpartum depression. Nevertheless, due to environmental pollution, some fish species may contain high level of heavy metals and in particular of methylmercury. During perinatal period, pregnant women who consumed contaminated fish may be exposed to high concentrations of methylmercury that may contribute to subtle alterations of central nervous system in unborn baby and young children. The objective of our study is a) to evaluate the omega 3 fatty acid status of French pregnant women who consumed fish and seafood products and b) to examine the methylmercury exposure related to the consumption of fish and seafood of French pregnant women. One hundred and fifty pregnant women were recruited in this project. This research has started in October 2005 and the first results will be available in September 2006. As indicators of phospholipids contents, we used the phospholipids contents of cheek cells and red blood cells membrane. Cheek mucosal cells and red blood cells, obtained at the first and at the last trimester during pregnancy, were analyzed using gas chromatography. In addition, we used methylmercury concentration in hair as indicator of methylmercury exposure during pregnancy. Maternal hair sample were obtained at the first and at the last trimester during pregnancy and analyzed using flow-injection cold-vapor atomic absorption spectrometry. Moreover, habitual fish intake of the pregnant women was assessed using food frequency questionnaire including detailed information about consumption of different fish species and seafood (fresh, canned, smoked and cooked). The finality of this study was to examine the relationships between phospholipids contents, methylmercury and habitual fish intake of French pregnant women. To conclude, this clinical study could be a useful tool to highlight the discussion concerning the benefit versus risk ratio of fish consumption in concerned population.