"These results, together with findings from other studies of women in the U.S. and the United Kingdom, provide additional evidence that moderate maternal fish intake during pregnancy does not harm child development and may on balance be beneficial," said Assistant Professor Emily Oken, lead author of the study.
The study has been published in the September issue of the American Journal of Clinical Nutrition.
The study's findings provide further evidence that the omega-3 fatty acids found in fish and compounds in breast milk are beneficial to infant development.
To reach the conclusion, the research team looked at 25,446 children born to mothers participating in the Danish Birth Cohort, a study that includes pregnant women enrolled from 1997-2002.
Mothers were interviewed about child development markers at 6 and 18 months postpartum and asked about their breastfeeding at 6 months postpartum. Prenatal diet, including amounts and types of fish consumed weekly, was assessed by a detailed food frequency questionnaire administered when they were six months pregnant.
During the interviews mothers were asked about specific physical and cognitive developmental milestones such as whether the child at six months could hold up his/her head, sit with a straight back, sit unsupported, respond to sound or voices, imitate sounds, or crawl.
At 18 months, they were asked about more advanced milestones such as whether the child could climb stairs, remove his/her socks, drink from a cup, write or draw, use word-like sounds and put words together, and whether they could walk unassisted.
The children whose mothers ate the most fish during pregnancy were more likely to have better motor and cognitive skills. For example, among mothers who ate the least fish, 5.7 percent of their children had the lowest developmental scores at 18 months, compared with only 3.7 percent of children whose mothers had the highest fish intake. Compared with women who ate the least fish, women with the highest fish intake (about 60 grams - 2 ounces - per day on average) had children 25 percent more likely to have higher developmental scores at 6 months and almost 30 percent more likely to have higher scores at 18 months.
Longer duration of breastfeeding was also associated with better infant development, especially at 18 months. Breastmilk also contains omega-3 fatty acids. The benefit of fish consumption was similar among infants breastfed for shorter or longer durations.