Fetal brain development starts early. Within the first 8 weeks of conception, the nervous system begins to develop. From week 9 until birth, the brain continues to mature, grow, and become more specialized. During the last trimester, the brain roughly doubles in size; neural tissue rapidly increases in volume, and by term, many neurons that will be present in adulthood have already emerged. Yet, infant brain development doesn’t stop at birth.
A newborn baby has a brain roughly 25% of its adult size, and brain growth and development continue to increase rapidly across the first 24 months of life. These early years are considered a critical period of importance for nutrition and brain development. In fact, many scientists believe nutrition is one of the most influential non-genetic factors affecting early brain development and cognitive outcomes.
Omega-3 DHA and Infant Brain Development
Omega-3 fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are nutrients of concern highlighted in pregnancy and infant development. Maternal intake of omega-3 fatty acids, particularly DHA, is reported to have effects on several infant outcomes, including, but not limited to, neurodevelopment and cognition.
DHA is a structural component of the phospholipid bilayer of cell membranes and concentrates in the cells of the central nervous system and brain. DHA makes up approximately 20% of the brain’s lipid content and is integral in neural development and function. DHA accumulates in the neural tissues with the greatest velocity (50-60 mg per day) during the last trimester of pregnancy, when brain growth and development peaks.
The cognitive impacts of DHA intake during pregnancy have been examined in research. Several observational studies have linked increased DHA intake in pregnancy to enhanced vocabulary comprehension, receptive vocabulary, verbal IQ, and higher cognitive scores in children. However, randomized controlled trials of DHA supplementation during pregnancy have shown little benefit to child neurodevelopment outcomes in infants born after full gestation. Infants born preterm, though, may have a different story.
Infants born preterm may miss the time of rapid DHA accumulation during the final trimester. Studies have found that preterm infants born before 30 weeks gestation are likely to have reduced DHA concentrations in neural tissues. Furthermore, ample evidence demonstrates that children born premature have a higher risk of cognitive deficits than their counterparts. For example, a 2017 systematic review that included over 64,000 children reported that preterm children had lower cognitive scores across several assessments and that several deficits persisted to secondary school age. Similarly, a review of case-controlled studies found that in infants born <33 weeks, IQ decreases by 1.5 points for every week born preterm.
(Did you know that omega-3 levels may also impact the risk of preterm birth? For more information, check out this article here ).
DHA supplementation for preterm infants
While DHA is vital for all infants, it is particularly critical for infants born prematurely. Research has found that preterm infants have lower neural tissue DHA levels than term-born infants. While studies have found that preterm infants struggle to overcome their DHA deficit after birth, supplemental DHA does increase their DHA level.
Several studies demonstrate this may improve health and cognitive outcomes. Tam et al. showed an association between higher early DHA levels and improved developmental outcomes at 30-36 months old. Sabel et al. found that in the initial 6 months, developmental scores were positively associated with DHA concentration. Finally, Henriksen et al. reported that compared to a control group, the intervention group who received supplemented human milk with a DHA concentration of 0.86% of total fatty acids scored significantly higher on problem-solving tested by the Ages and Stages Questionnaire at 6 months of age.
Still, most of the results published in DHA supplementation in preterm infants assess short-term developmental benefits, and no effects on long-term development have been shown.
Study Investigates the Effects of an Omega-3 Intervention on Intelligence of 5-Year-Olds
The New England Journal of Medicine published a study in October of 2022 that assessed the general intelligence of children at 5 years of age who had been enrolled in a previous trial that evaluated the effect of neonatal DHA supplementation on the prevention of bronchopulmonary dysplasia.
The original trial included infants born before 29 weeks’ gestation who were randomly assigned to receive daily enteral emulsions that contained 60 mg of DHA per kilogram body weight or a control emulsion (soy based) until 36 weeks or discharge home, whichever occurred first. The children in the follow-up study included 241 in the DHA group and 239 in the control group. The children were assessed at 5 years of corrected age to determine their full-scale intelligence quotient (FSIQ) score.
The researchers found that the mean FSIQ scores were modestly higher (95.4 +/- 17.3) in the DHA group 5 years later compared to the control group (91.9 +/- 19.1). Although a difference of 3.5 FSIQ points may seem insignificant, it has been reported that every 1-point increase in FSIQ scores increases worker productivity by 1.8-2.4%, leading to potential gains in economic earnings and societal contributions.
The results of this study support the current recommendations for preterm infants born before 29 weeks gestation, which includes supplementation with approximately 60mg of DHA per kilogram per day in addition to what is being supplied through breast milk or preterm infant formula.
Ensuring Optimal DHA Intake During Pregnancy Optimizes Infant Health
While there is no consensus on DHA recommendations for pregnant or lactating women, several leading organizations, such as the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Pediatrics (AAP), and the March of Dimes, recommend intake of 200-300mg/day of DHA in the prenatal diet, equating to about 8-12 ounces of low-mercury seafood each week. Still, organizations like The American Dietetic Association (ADA) recommend a higher intake of 500mg/day of DHA in the prenatal diet. Yet, evidence indicates that most women are far from meeting either of these recommendations.
A 2018 study that investigated the dietary intake of EPA and DHA omega-3 fatty acids via seafood consumption among women who were pregnant or of childbearing age found that average consumption was approximately 3.08 ounces per week, which is far below the recommended 8-12 ounces.
While inadequate consumption may be multifactorial, including lack of access due to location or financial reasons, mercury consumption is often cited as a cause of concern. While it is true that seafood can also contain substances that can be harmful if consumed in excess, it’s crucial to ensure that omega-3 needs are being met in a way that maximizes benefits and minimizes risk.
Therefore, increasing the intake of omega-3 fatty acids can be done through low mercury-containing seafood and supplementation. With regard to the former, most experts recommend that people familiarize themselves with the SMASH fish — sardines, mackerel, Anchovies, salmon and herring — as these offer the most bang for your buck if you are specifically seeking out rich sources of EPA and DHA and pose very little risk in terms of containing mercury and other contaminants.
Finally, DHA intake efforts should not cease after birth. Infant DHA needs are elevated during the early stages of life as neurodevelopment continues. Following delivery, infants rely on enteral sources to meet their DHA needs, whether through breast milk or formula.
Maternal DHA status influences DHA concentration in breast milk. Research has found mean breast milk DHA content in the U.S. to be low, likely due to inadequate consumption of DHA-rich food sources. Therefore, mothers, particularly those who are breastfeeding, should continue to meet omega-3 intake needs and ensure formulas contain adequate DHA content.
Know Your Numbers
Scientists have reported that there is insufficient data to firmly establish a target or ideal prenatal red blood cell (RBC) DHA level. However, multiple sources have identified a preliminary threshold for RBC DHA at ~5%. OmegaQuant’s Dr. Bill Harris and Dr. Kristina Harris Jackson published a paper in 2018 advocating a threshold red blood cell DHA level of 5% as a reasonable initial target to support pregnancy outcomes.
This recommendation is in line with several other authors, including Carlson et al., who indicated that RBC DHA levels of 4.3% and 3.5% in pregnant women are “very low” and “exceedingly deficient,” respectively.
Furthermore, a 2022 statement issued by the International Society for the Study of Fatty Acids and Lipids (ISSFAL) recommended a similar threshold. According to their report, replete omega-3 status is represented by omega-3 levels >4.9%. This means if a pregnant woman (or woman who is trying to conceive) has an RBC DHA of <5%, she should be encouraged to increase DHA intake through low-mercury, high-DHA fish or DHA supplementation. Current recommendations suggest screening for omega-3 status early in pregnancy through blood testing. Prenatal and mother’s milk DHA tests are also available.