Eating oily fish during pregnancy can reduce anxiety, a new study has found.

Many women experience stress and anxiety during pregnancy, but long-term anxiety could have a negative impact on the mother and the fetus' health. Researchers said that pregnant women must a have a well-balanced diet and not follow any special diets during pregnancy. Certain diets that do not include meat and fish leave out vital nutrients essential for the growth and development of the baby.

The study was conducted by researchers from the Children of the 90s at University of Bristol and the Federal University of Rio de Janeiro, Brazil which found that a diet without oily fish could increase anxiety in women.

The study was based on data available from 9,500 pregnant women.

Women who are pregnant or breastfeeding are advised to consume at least 8 ounces but no more than 12 ounces of seafood each week and not eat certain types of fish that are high in mercury-a toxin that can harm the nervous system of a fetus or the developing child, according to The Dietary Guidelines for Americans. Other fish such as shark, swordfish, king mackerel, and tilefish along with uncooked fish and poultry should be avoided during pregnancy.

Researchers in the study found that pregnant women who didn't eat any kind of seafood during pregnancy were 52 percent more likely to be stressed at 32 weeks of pregnancy than women who regularly ate fish throughout their pregnancy. Study results show that eating two meals of white fish and one meal of oily fish per week could lower stress levels in pregnant women.

The co-relation between lower stress and fish consumption remained even after researchers accounted for other anxiety causing factors such as maternal smoking, drinking and family adversity.

Also, women who were vegetarian were about 25 percent more likely to suffer from stress during pregnancy.

"It is possible, but not proved, that this association with fish is due to the omega-3 fatty acid content of the fish. For vegetarians there are dietary sources of omega-3 fatty acids especially flax oils, algae oils and nuts and seeds such as walnuts. There are also products such as omega-3 eggs and milk on the market which they could choose. Some vegetarians are happy to eat fish from time to time and we would encourage this especially as we are not sure what ingredient in fish is the most effective," said Dr Pauline Emmett, senior dietician at Children of the 90s, and a co-author of the study, according to a news release.

The study is published in the journal PLOS One.

Note that pregnant women should always consult their doctor before making any changes to their diet.