Maternal nutrition plays a critical role in fetal development and can influence adult onset of disease. Linoleic acid (LA) and alpha- linolenic acid (ALA) are major omega-6 (n-6) and n-3 polyunsaturated fatty acids (PUFA), respectively, that are essential in our diet. LA and ALA are critical for the development of the fetal neurological and immune systems. However, in recent years, the consumption of n-6 PUFA has increased gradually worldwide, and elevated n-6 PUFA consumption may be harmful to human health. Consumption of diets with high levels of n-6 PUFA before or during pregnancy may have detrimental effects on fetal development, and may influence overall health of offspring in adulthood. This review discusses the role of n-6 PUFA in fetal programming, the importance of a balance between n-6 and n-3 PUFAs in the maternal diet, and the need of further animal models and human studies that critically evaluate both n-6 and n-3 PUFA content in diets.