When expectant mothers enjoy a diet rich in fish, their babies are more likely to develop better, physically and cognitively, than babies born to mothers who eat less fish. When babies are breastfed for a substantial length of time, their developmental progress closely resembles that of babies born to mothers who ate the most fish during pregnancy. Both fish and breast milk contain significant amounts of omega-3 fatty acids, thought to be an essential element in childhood development, according to a recent Danish study of infants and their mothers’ diets.

The research team, consisting of investigators from both the United States and Denmark, examined records dating from 1997 to 2002 involving 25,446 babies born to mothers enrolled in the Danish Birth Cohort at that time. As a part of the birth cohort, expectant mothers recorded their diets, including how much and of which type of fish they ate, six months into their pregnancies. Mothers reported their babies’ developmental progress at 6 and 18 months and they revealed how long they breastfed their children.

The developmental markers of particular interest included each 6-month-old child’s ability to crawl, hold up his or her own head, imitate sounds, respond to voices and sound, sit up unassisted, and sit up with the baby’s back straight. Markers at 18 months included the child’s ability to climb stairs, drink beverages from a cup, make word-like sounds, remove his or her socks, use words together appropriately, write or draw, and walk without assistance.

Fish intake of 2 ounces per day, on average, was the highest amount consumed by mothers in the study. These mothers had children 25% more likely to perform well at 6 months and 30% at 18 months than the children of mothers who ate less fish during pregnancy.

Children breastfed longest, 18 months or more, were developing at the same satisfactory rate as the babies born to mothers who consumed the most fish during pregnancy. Babies breastfed for the shortest time were more likely to earn lower developmental scores, as did the babies born to mothers who ate less fish.

Previous studies in the US also produced the same enhanced development in children born to mothers who consumed more fish but the presence of mercury in some breeds of fish seemed to counterbalance developmental progress in some cases. Although no mercury levels were assessed in the fish the women ate during the Danish study, the mothers ate more cod, herring, mackerel, plaice, and salmon than other fish. All of these fish are known to be lower in mercury than many other fish, leading the research team to suggest mothers choose these fish, containing lower mercury, during pregnancy and nursing for optimum safety and childhood development.

The September issue of the American Journal of Clinical Nutrition carries the full details of the Danish study.

Source: Harvard Medical School