Importance of fatty acids in the perinatal period.

Long-chain polyunsaturated fatty acids (LC-PUFAs) influence a variety of cellular and physiological processes during the perinatal period by serving as membrane components, precursors of eicosanoids and docosanoids, and nuclear receptor activators. These processes include the growth of neural cells and signal transduction, the growth and differentiation of adipocytes, and the function of regulatory T cells. LC-PUFA levels depend on these fatty acids' dietary availability and their endogenous synthesis from essential fatty acids, which is known to differ among subjects according to fatty acid desaturase genotype. Intrauterine placental mechanisms support the preferential transfer of LC-PUFAs from the mother to the foetus. After birth, breast milk provides arachidonic acid and docosahexaenoic acid, although not in amounts that can prevent lower percentages in infant plasma than in umbilical cord blood plasma. The available epidemiological data suggest associations of perinatal LC-PUFAs with later body weight, the risk of allergic diseases and cognitive performance. Randomised clinical trials that compare different maternal or infant intakes of n-3 LC-PUFAs or combinations of n-3 and n-6 fatty acids so far have not led to firm conclusions about the optimal LC-PUFA status of pregnant women or infants, but there are good indications of beneficial effects of a higher pre- or postnatal docosahexaenoic acid status on visual function and asthma risk.