The researchers say the findings, published in the Journal of Pediatrics, highlight the importance in child development of prenatal exposure to the omega-3 acids and conclude "benefits from eating fish with low-contaminant levels and high omega-3 contents, such as trout, salmon and sardines, far outweigh potential risks even during pregnancy."

Researchers at the Universite Laval in Quebec City and Wayne State University in Detroit measured docosahexaenoic acid, or DHA, concentration in the umbilical cord blood of 109 infants at birth.

"DHA concentration in the umbilical cord is a good indicator of intra-uterine exposure to omega-3s during the last trimester of pregnancy, a crucial period for the development of retinal photoreceptors and neurons," study leaders Eric Dewailly and Gina Muckle said in a statement.

Tests on infants at 6 and 11 months revealed their visual acuity as well as cognitive and motor development closely linked to DHA concentration in the umbilical cord blood.