Other links: Heart Health | Mental Health | Mothers & Infants | Fats and Brain

ESSENTIAL FATTY ACIDS IN PREGNANCY: EATING FOR TWO

Good nutrition for motherhood begins before conception, providing a head start for both the mother and baby. This is especially true for nutrients, such as essential fatty acids*, that are below the radar screen of many women and their doctors. Two polyunsaturated fatty acids, AA and DHA, are building blocks of brain cells, the vascular system, and other tissues. DHA is concentrated in the retina of the eye and important for visual function. DHA facilitates communication between brain cells, a critical brain function. The developing fetus depends on the mother's nutrition to obtain these fatty acids. The mother's supply comes from the foods she eats and her own tissues.

AA and DHA are vital to the mother's health to support growth of the placenta and developing fetus, maintain her own tissues, and make substances, such as prostaglandins, which are important in childbirth.

AA and DHA for the Fetus: The mother has two ways of providing AA and DHA for the fetus. One is to make them from precursor fatty acids and the other is to consume them in foods. For AA, either choice appears sufficient. The body makes AA from linoleic acid, the most plentiful polyunsaturated fatty acid in western diets. Meats and fish have some AA too. In western countries, there appears to be plenty of AA for healthy development of the fetus and young infant.

DHA, an omega-3 fatty acid, is more limited for two reasons. Few foods other than fish and shellfish contain DHA and fish consumption is very low in many western countries. Women in the U.S. have one of the lowest intakes of fish in the world. Women, especially vegetarians, who eat no fish obtain little DHA and have less in their tissues than women who consume fish. The good news is that DHA is becoming more available through fortified foods like omega-3 eggs and in dietary supplements.

Obtaining DHA from its Precursor: The second source of DHA is conversion of the precursor, alpha-linolenic acid, to EPA and DHA. However, unlike the formation of AA, these conversions are highly inefficient with 5% or less being converted to EPA and less to DHA. For this reason, relying solely on alpha-linolenic acid to supply DHA may not provide the amounts needed by the brain during fetal development. The best food sources of alpha-linolenic acid are flaxseed, canola oil, English walnuts, and soybean oil.

The developing fetus greatly prefers preformed AA and DHA over their precursors. AA and DHA are avidly taken up by the placenta from the mother's circulation and passed on to the fetus. The greatest accumulation of these fatty acids occurs in the last trimester. Moreover, simply consuming more alpha-linolenic acid does not increase the DHA level in the mother's circulation or breast milk. To make matters worse, diets high in linoleic acid, such as most western diets, discourage the small conversion of alpha-linolenic acid to DHA.

Infants of mothers who consumed DHA regularly during pregnancy have higher levels of DHA than infants of mothers consuming little DHA. These infants also have more DHA in their body fat, which provides insurance against a possible low intake after birth. Starting life with higher DHA is an advantage for the young infant whose brain grows for at least the next two years.

FEEDING INFANTS

Mothers who breast-feed their babies provide AA and DHA in their milk. The amount of AA in breast milk is fairly constant among women, but DHA varies widely, depending on the mother's food choices. Mothers who eat fish during nursing have substantially more DHA in their milk - up to 10 times more - than women who do not eat fish.

Infants fed formula will obtain AA and DHA only from those formulas that have these fatty acids added to them. Many formulas are now available with AA and DHA and these are preferable to those without them. In some cases, the amounts of DHA in infant formula, which are limited by law, are higher than some women's breast milk. Using supplemented formula assures that the infant receives the fatty acids needed for continued brain growth.

Preterm infants have less body fat at birth and have had less time to accumulate AA and DHA from the mother. As a result, these babies are born with less of these fatty acids and are fed special formula containing AA and DHA. Once they are ready for regular infant formula, it is preferable to continue providing formula containing AA and DHA.

CHILD-BEARING YEARS

Women favor their own health and a healthy pregnancy by having healthy eating habits. For that reason, foods rich in omega-3s, particularly EPA and DHA, should be a regular part of good nutrition. Before pregnancy, women consuming seafood or other foods with these fatty acids will ensure their availability from the earliest stages of pregnancy through term. After birth, maintaining good nutrition meets the demands of breast-feeding and helps replenish nutrients reduced during pregnancy.

Women who have already had one or more children have less EPA and DHA available for another pregnancy. It has been shown that women who have had several children have less DHA in their tissues than women having their first baby. Unless these losses are replaced by consuming fish and shellfish or other sources of EPA and DHA, less DHA will be available for another pregnancy.

*Words in blue are described in the glossary.