As prescribed in appropriate sections on this website and in the video on this topic, the expert committee have met at the National Institutes of Health in Bethesda, Maryland in 1999 recommended a minimal intake of 300 mg of DHA daily during pregnancy (particularly the last trimester) and lactation (to provide for breast milk levels of DHA to reach approximately 0.35% of total fat). If DHA is being consumed form fish during such times, North American advisories have placed restrictions on consumption of predatory fish such as shark, swordfish, fresh tuna, and frozen tuna (excluding canned tuna) based on their mercury levels. Most other types of fish (such as wild or farmed salmon, wild or farmed rainbow trout, others) when consumed 2-3 times per week will provide average daily intakes of DHA approaching 250-300 mg without exposure to risk levels of contaminants based on analyses and assessments from health groups in North America and cut-offs on contaminant intakes (including methyl mercury and PCBs) established by environmental and health agencies in North America.
With respect to DHA intakes during the first trimester of pregnancy, DHA intakes have levels above 300mg per day are common place in Japan and other parts of the world where a high consumption of fish/ fish oils is practiced. While it may be anticipated that the optimal intakes of DHA carry the first trimester do not need to be as high as those recommended as those recommended during the last trimester (300mg DHA/day), there is no evidence that such intakes of DHA during the first trimester posed any health risks. Of course, this assumes that one is ingesting a high quality safe supplement and that the consumer can readily tolerate such products as the vast majority of people can. DHA does accumulate in the developing brain and through out the body of the baby through out all trimesters of pregnancy.
Some studies have shown better mental performance (mental development index) and hand-eye co-ordination (measured as the psychomotor development index) when infant formula containing 0.35% by weight of the fat of DHA have been compared to infant formula lacking DHA. As mentioned earlier, 300mg of DHA per day can be expected to bring the breast milk level of DHA up to above 0.35% by weight of total milk fat whereas 100mg of DHA per day will most likely not bring the DHA content up to this target.
The scientific evidence is most convincing that DHA is critical in the developing brain. The mechanisms by which omega-3 fatty acid deprivation may adversely affect brain development is considered to involve many mechanisms ranging from membrane biogeneseis, altered neurotransmission, others.