DHA, docosahexaenoic acid, commonly known as brain gold, is an omega-3 polyunsaturated fatty acid. Currently, the main sources of DHA are fish oil and microalgae oil. DHA is present in fish oil in the form of ethyl ester and in microalgae oil in the form of triglyceride. Triglyceride DHA has more advantages than ethyl ester in terms of metabolic absorption rate and bioavailability, stability and safety in human body. 1, the role of DHA DHA is a kind of unsaturated fatty acid, has the function of lowering blood pressure, lowering blood lipids, lowering cholesterol and regulating the body’s immunity, and can reduce blood viscosity, inhibit the formation of blood clots and prevent the occurrence of cardiovascular disease. It may improve the hypercoagulable state of blood that exists during pregnancy. DHA is an important fatty acid component in the brain, nerve and vision cells, which has a key role in the development of vision and nervous system of infants and children. Since the fetus itself cannot synthesize DHA, it must be obtained from the mother through the placenta, so DHA supplementation during pregnancy helps the health of pregnant women and the development of fetal brain and vision system. 2.Some studies on DHA supplementation during pregnancy There is no uniform statement about the effect of DHA on pregnant women. However, some studies have shown that DHA supplementation during pregnancy can increase the birth weight, length and head circumference of newborns to some extent, and some other studies have concluded that DHA can reduce the incidence of complications during pregnancy. An early study concluded that supplementation with EPA (another unsaturated fatty acid) and DHA reduced the incidence of recurrent miscarriage in patients with persistent antiphospholipid syndrome and achieved good pregnancy outcomes. However, the results of a recent RCT showed that supplementation with omega-3 polyunsaturated fatty acids was not effective in reducing the rate of preterm birth. 3, which foods contain DHA DHA is widely found in seafood, eating seafood can be supplemented with DHA, animal liver and egg yolk also contains a small amount of DHA, for some common meat, such as cattle and pig fat is saturated fatty acids, does not contain DHA. cereals, potatoes, starch, vegetable oils, margarine, butter, beans, milk, vegetables, fruits, etc. also almost all do not contain DHA. 4, DHA should not be too much DHA is important to maintain human health, but not the more intake the better. DHA is a highly unsaturated fatty acid, vulnerable to the attack of active free radicals in the body and trigger peroxidation chain reaction, that is, lipid peroxidation, which has damage to the cell membrane. 5, the appropriate amount of DHA According to the Chinese dietary structure and habits, and comprehensive reference to the international authorities of the recommended intake of DHA, it is recommended that the recommended intake of DHA for different groups of people in China: adults 220mg / d, pregnant and lactating women 300mg / d, infants and children 100mg / d (infants and children can also get DHA from breast milk), children and adolescents 160 ~ 200mg / d, different groups of people. 200mg/d, different people should supplement DHA according to their dietary habits and their own needs.