How important are omega-3 fatty acids in a pregnant woman’s diet?
Pregnant women are advised to eat about 12 ounces of fish a week, including one of oily fish. Raw fish or seafood, swordfish, tilefish, king mackerel, and shark are best avoided due to risk of food poisoning and heavy metal toxicity.
Eating fish is good for general health, but particular importance is placed on the omega-3 fatty acids in oily fish for maternal and fetal health. They are believed to bring a range of benefits such as helping the baby’s visual and nervous systems to develop.
Omega-3 fats are a particular class of “healthy” fats, found in certain nuts and seeds (as alpha-linolenic acid) and in oily fish such as salmon, trout and sardines (as eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA).
A 2007 study of 11,875 pregnant women, published in the medical journal Lancet, showed that eating more than 340 grams (12 ounces) of seafood a week — the equivalent of about two and a half portions — is beneficial to the child’s neurodevelopment. It also suggested that eating less than this amount may bring an increased risk of lower verbal intelligence and social development.
The researchers write, “We recorded beneficial effects on child development with maternal seafood intakes of more than 340 g per week. These results show that risks from the loss of nutrients were greater than the risks of harm from exposure to trace contaminants.”
Professor Michael Crawford of London Metropolitan University, UK, comments, “Unlike the rest of the body, the brain is mainly made of fat. It needs these fatty acids for brain growth and development. We are deeply concerned that this has been more or less neglected in the current advice and unless there is a change in nutrition advice to take the brain into account, then mental disorders are going to continue to grow at an alarming rate.”
Other research has linked inadequate omega-3 intake with an increased risk of low birth weight. A study based on 700 women in India found that not eating fish at all during pregnancy was associated with a 2.5-fold increased risk of low birth weight. Added to the other likely benefits of omega-3 consumption during pregnancy, this does support the argument for ensuring adequate levels during gestation.
Professor Gerard Hornstra of Maastricht University in the Netherlands, explains that essential fatty acids are crucial for fetal development, and must be consumed as part of the mother’s diet. Pregnancy is associated with a decrease in fatty acid levels, so the baby’s fatty acid status may not be ideal.
“Neonatal fatty acid status correlates positively with birth weight, birth length, and head circumference,” he writes. “This suggests that the ratio of n-3 to n-6 fatty acids in the maternal diet should be increased.” He adds that “it seems prudent to minimize the consumption of trans fatty acids during pregnancy”.
In addition to the potential benefits for the baby, omega-3 fatty acids may also be a factor in perinatal depression. There has been considerable interest in the potential of omega-3 fatty acids as a natural antidepressant, due to their role in serotonin functioning. A 2009 study looked at the relationship between blood levels of omega-3 fatty acids and depression in 16 depressed and 22 non-depressed women in the third trimester of their pregnancies.
High levels of the omega-3 fatty acid known as DHA and high levels of total omega-3 fatty acids were both significantly linked with a reduced risk of depression. The researchers believe it is possible that during pregnancy omega-3 fatty acids may be preferentially diverted to the baby, putting women at increased risk of deficiency.
Further research points to a protective effect against depression when pregnant women take omega-3 fatty acid supplements. One study gave 3.4 grams per day of omega-3 fatty acids to pregnant women with major depressive disorder, and found reduced depressive symptoms after two months, compared to placebo. The women also had lower scores in an assessment of postnatal depression.
A 2010 review of seven clinical trials found significant results in only three. The reviewers, from Nova Southeastern University in Florida, write that the findings are inconclusive, but further investigation of omega-3 fatty acids is warranted because they did improve depression scores and appeared to be safe during pregnancy.
Larger scale studies need to be carried out. However, the outlook is promising, and suggests that omega-3 fatty acids may be useful for protecting the baby’s health and combating maternal depression during and after pregnancy.
Oken, E. et al. Maternal fish intake during pregnancy, blood mercury levels, and child cognition at 3 years in a US cohort. The American Journal of Epidemiology, Vol. 167, May 2008, pp.1171-81.
Hibbeln, J. R. et al. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. The Lancet, Vol. 369, February 17, 2007, pp. 578-85.
Rees, A. M. et al. Omega-3 deficiency associated with perinatal depression: Case control study. Psychiatry Research, Vol. 166, April 30, 2009, pp. 254-59.
Su, K. P. et al. Omega-3 Fatty Acids for Major Depressive Disorder During Pregnancy: Results From a Randomized, Double-Blind, Placebo-Controlled Trial. The Journal of Clinical Psychiatry, Vol. 69, April 2008, pp. 633-34.
Hornstra, G. et al, Essential fatty acids in mothers and their neonates. The American Journal of Clinical Nutrition, Vol. 71, May 2000, pp. 1262-69.
Olsen, S. F. and Secher, N. J. Low consumption of seafood in early pregnancy as a risk factor for preterm delivery: prospective cohort study. The British Medical Journal, Vol. 324, February 2002, p. 447.
Muthayya, S. et al. The effect of fish and omega-3 LCPUFA intake on low birth weight in Indian pregnant women. The European Journal of Clinical Nutrition, Vol. 63, March 2009, pp. 340-46.
Borja-Hart, N. L. and Marino, J. Role of omega-3 Fatty acids for prevention or treatment of perinatal depression. Pharmacotherapy, Vol. 30, February 2010, pp. 210-16.