Eating fish while pregnant increases the risk of childhood obesity, especially in kids between 4- and 5-years-old. A new study found that mothers who eat fish three or more times a week during pregnancy are more likely to have overweight children than pregnant mothers who ate little or no fish.
According to an L.A. Times report, the researchers could only come up with two possible reasons why eating fish while pregnant would have weight-related effects. One possibility is that the Omega-3 fatty acids commonly found in fish could influence fetal stem cells to separate and become fat cells. The other explanation could be that contaminants, like mercury, within the fish may upset fetal hormones related to digestion and encourage increased fat storage.
However, to blame pollutants for damaging stem cells would be “speculative,” at best, as the researchers had no way to accurately measure the amount of contamination present in the fish consumed by the women.
The large-scale study, conducted in the U.S. and 10 European countries, looked at the effects of fish consumption during pregnancy. A report of the findings was published February 15 by JAMA Pediatrics.
Researchers followed 26,184 pregnant women and their children, born between 1996 and 2011. The women were given a questionnaire about their food intake, while the growth patterns and weight status of the children were measured every two years up to age six.
On a weekly basis, mothers in some European countries like Belgium and Ireland reported eating less than half a serving of fish while pregnant. In other countries like Spain and Portugal, as much as seven servings per week were eaten. Women in the U.S., mostly in Massachusetts, said they ate an average of one to two servings each week.
Up to age two, the children born to women who ate the most fish while pregnant were 22 percent more likely to have had a rapid increase in growth when compared to the children of women who ate less servings. Additionally, the children of mothers who ate a lot of fish were 14 percent and 22 percent more likely to suffer from obesity at ages four and six, respectively.
According to study coauthor Leda Chatzi from the University of Crete, offspring born to women who ate at least one serving, but less than three servings of fish per week had the lowest risk of childhood obesity.
Over the past few years, many public health campaigns have encouraged eating fish while pregnant. Several studies have pointed out that pregnant women who eat at least 12 ounces of fish per week tend to have children with a higher IQ, enhanced motor coordination, as well as better communication and social skills.
Both the Food and Drug Administration and the Environmental Protection Agency recommend that women eat two to three servings, or roughly 8 to 12 ounces, of fish every week while pregnant. The agencies’ recommendation published in July, 2014, advised pregnant mothers to avoid fish highly likely to be tainted with mercury, like swordfish, shark, and king mackerel. They, instead, suggest choosing salmon, shrimp, pollock, tuna, catfish, and cod.
Experts agree that the Omega-3 fatty acids found in fish are essential for the proper development of fetal brain and retinal tissues. These acids may also affect the length of fetal gestation, as well as potentially reducing emotional issues experienced by the mother while pregnant.
While the researchers did collect information on the consumption of different fish types, there was not enough data to determine specific species, cooking methods, or water source.
The study authors found that the weight-related effects of eating fish while pregnant were even more prominent when the child was female. In the near future, the team intends to study why the risk of childhood obesity is higher for female babies than it is for males.
[Photo by Fiona Goodall/Getty Images]