The study specifically looked at maternal intake of fish and omega-3s, and observed childhood neurodevelopment at the age of 6 months and 1 year. 81,697 mother-child pairs at the age of 6 months were evaluated, in addition to 77,751 mother-child pairs at the age of 1 year.
Maternal fish intake during pregnancy was independently associated with a reduced risk of delay in problem-solving skills at the age of 6 months, as well as in fine motor skills and problem solving by the time the child reached one year of age. Looking at omega-3 fatty acids specifically, the authors concluded that an increased maternal intake was associated with a reduced risk of delay in fine motor skills ant 6 months, and in fine motor skills and problem solving at one year of age.
Maternal intake of omega-6 fatty acids was associated with a reduced risk of delay in communication and fine motor skills at 6 months old, and in gross motor skills, fine motor skills, and problem solving at one year old. However, it was shown that a high omega-6:omega-3 ratio was positively associated with an increased risk of delayed problem solving at one year old.
"Besides DHA, arachidonic acid (AA) is also an important PUFA," the authors said. "It is abundant in the gray matter, and is a required precursor for eicosanoids such as PGs, thromboxane, and leukotriene, which are potent regulator and inflammatory substances […] However, for the omega-6/omega-3 ratio, detrimental effects emerged for the problem-solving domain in the highest quintile group."
The reason for this is unclear, the authors said, but limited evidence suggests that AA has a role in heightening a risk of preterm birth, which is tied deeply to neurological development. Further, they conclude that further research is needed to see if beneficial effects present at such an early age persist into areas such as mental health and behavior later in life.
"In terms of clinical implications, the evidence supporting the efficacy of omega-3 PUFAs in child neurodevelopment is still inconsistent," the authors concluded. "However, because there is considerable evidence of the beneficial effects of fish consumption on neurodevelopment, we advocate that fish - especially fatty fish - be recommended to pregnant women, as long as the fish species are limited to those not containing methylmercury […] more follow-up is needed to explore other aspects of neurodevelopment such as mental health and behavior."
Kei Hamazaki, Kenta Matsumura, Akiko Tsuchida, Haruka Kasamatsu, Tomomi Tanaka, Mika Ito, Hidekuni Inadera, Japan Environment and Children's Study Group, Maternal dietary intake of fish and PUFAs and child neurodevelopment at 6 months and 1 year of age: a nationwide birth cohort—the Japan Environment and Children's Study (JECS), The American Journal of Clinical Nutrition, Volume 112, Issue 5, November 2020, Pages 1295–1303