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Why Do I Need DHA During Pregnancy?

Pregnant woman
Highlights
  • DHA builds healthy tissues in many organs throughout fetal development and after birth
  • A developing fetus rapidly accumulates DHA in the third trimester
  • DHA during pregnancy improves birth and infant outcomes

You’ve heard that taking DHA during pregnancy will help your baby’s brain development. But you’re probably thinking, “My mom never took DHA when she was pregnant with me, and I’m brilliant!” Ok, you are pretty smart—after all, you’re reading this article. Maybe your mom’s DHA intake was sufficient. Maybe she has gene variations that put her at low risk for DHA deficiency. And maybe after you read this article, you’ll decide that you don’t need to increase your DHA intake during pregnancy. But first, we’d like to help you gather information to make your own decision. Let’s talk DHA.

DHA builds healthy bodies

Omega-3 DHA (docosahexaenoic acid) is a long-chain polyunsaturated fatty acid (PUFA) that is critical for building flexible, responsive cell membranes and facilitating healthy immune reactions throughout our lives. In other words, it’s a fat that does more than mock you from your muffin top. For the basics on DHA and other omega-3 fatty acids, see our article “An Introduction to Omega-3 Fats”.

During fetal development, DHA rapidly accumulates in specific tissues where it is needed upon birth—the brain, eyes, liver, adipose (fat), and skeletal muscle. Once an infant is born, DHA is important for healthy vision, healthy cognition, and a healthy immune system.3-5 Statistically, mothers with high DHA levels during pregnancy have longer pregnancies6-8 and fewer preterm births (<34 weeks).6,8,9 Babies born to these moms tend to have higher birthweight,6,10,11 and experience earlier gains in visual12-14 and cognitive development.12,15,16

Emerging evidence about DHA and pregnancy

Recent research indicates that the benefits of DHA during pregnancy may not be limited to brains and eyeballs. Two areas of emerging evidence suggest that DHA may also influence a child’s future body composition and their risk for allergies–both of which represent increasingly prevalent health concerns for today’s youth.17,18

DHA and childhood obesity

Chubby little kids are adorable, but at a certain point they’re at significant risk for developing metabolic problems such as blood sugar imbalances, fatty liver disease—all before they can even drive!19,20  A few observational studies suggest that high levels of DHA during pregnancy21 and breastfeeding22 are correlated with lower child adiposity, lower BMI39, and greater lean muscle mass. Further evidence of a link between DHA and childhood adiposity comes from a recent interventional study examining how DHA during pregnancy affects later body composition of children born to mothers with a heightened risk of having an obese child, either due to obesity or pregnancy-related blood sugar imbalances.23 This study found that by the time the children were four years old, 40% were obese. However, women who took 800 mg DHA per day during pregnancy, and breast fed, had children with significantly less adiposity at four years old, compared to women who didn’t breastfeed or take DHA. 

Despite these promising results, the role of DHA in childhood obesity is unclear. One study examined children born to women who consumed 10 ml cod liver oil (2 teaspoons, ~800 mg DHA) per day during pregnancy, and for three months postpartum while breastfeeding.24 By seven years old, the children had higher cognitive functioning, but their BMIs were not significantly different from the children whose mothers didn’t take extra DHA. So, it’s still too soon to draw conclusions about the effects of DHA on childhood BMI, and if DHA supplementation during pregnancy is an effective intervention for women at high risk for having overweight or obese children. Let’s keep our eyes on this.

DHA and allergies

It is also possible that consuming extra DHA during pregnancy can lower children’s risk of developing certain immune problems. Recently, a large, well-controlled clinical trial studied children born to mothers who took 800 mg DHA during pregnancy, and whose parents had a history of these type of dysfunctions.25  There were two types of data: reports of the child’s symptoms by the parents, and reactions to allergens in a pediatric skin-prick test. 

By six years of age, the study investigators found that parents of children in the DHA group were no more likely to report symptoms in their children than parents of children in the control group (i.e., parents who had a history of immune problems but didn’t take extra DHA during pregnancy). However, in the skin-prick test, the children in the DHA group had significantly less sensitization to dust mites compared to the control group (34% reduction). There were also promising, yet statistically nonsignificant reductions in sensitization to peanuts and cashews (38% and 48%, respectively). Six other potential immune reactive molecular species showed no decrease in sensitivity with DHA. This clinical trial illustrates the difficulties of coming to “final conclusions” about the effect of DHA on complex physical responses.


You may be wondering: How can a 34% reduction in dust mite sensitivity be statistically significant, while larger reductions in peanut (38%) and cashew (48%) sensitivities are not?!

It’s because there was a small number of children with peanut or cashew sensitivity in the control group. (Keep reading, it’s worth the brain strain.) Any measurement you make is actually part of a range of numbers that you can confidently detect.  The range is basically the ‘buffer zone’ around the measurement. But with fewer cases to study, the buffer zone needs to be larger in order to be accurate. (Home stretch.) If the buffer zone becomes so large that it overlaps with the ‘no effect’ zone, then the result isn’t statistically significant. This doesn’t mean there’s no effect, it just means that we can’t detect an effect with the number of people studied. (You are now a certified nerd. Lab coat, stats book, and pedantry are in the mail!)


While the current state of research on DHA’s role in improving obesity and allergy risk is still under investigation, you can see that these findings represent promising avenues of future research into how supplementation with DHA may help mitigate these increasing risks in children. 

DHA in the last trimester

A developing baby accumulates DHA throughout the pregnancy, but especially during the last trimester. From week 35 to week 40, on average, a fetus gains 45% more weight.26 Over the same period, DHA accumulates as much as 840%!1 From week 35 to week 40, DHA is estimated to accumulate: 450% in skeletal muscle, 570% in the brain, 680% in the liver, 840% in adipose tissue.1,2

As the fetus ramps up DHA absorption, that same DHA is lost from the mother. (Thus begins a lifetime of your kid taking your stuff without asking.) If the mother already has low DHA status, then this last-minute demand puts her at risk of DHA deficiency, which can have serious implications. Low maternal DHA upon birth has been associated with an increased risk of postpartum mood disturbances.27,28 This is especially problematic for mothers who intend to breastfeed, since DHA deficiency will be reflected in their milk and, ultimately, could also put the infant at risk for DHA deficiency. It’s difficult to say how much DHA storage an infant is born with (based on animal studies, maybe 1-2 months29). Incredibly, researchers have been able to predict DHA deficiency in two month-old babies by their level of visual acuity. The newborns who were deficient at two months also had lower language skills at 18 months.12

The good news is that mothers who consume more DHA in just the last few weeks of pregnancy give birth to babies with significantly higher DHA levels.30  This means that it’s never too late to increase your DHA intake.

DHA and implications for premature birth

Given the importance of the last trimester for fetal DHA accumulation, you may be wondering what this means for infants born prior to normal term. Although such a birth means that your infant misses out on some of that last-minute DHA boost, providing DHA through breast milk31 or DHA-supplemented formula13,31 can make up for it. Multiple clinical trials have shown that preterm infants, including those born before 28 weeks, benefit significantly from DHA supplementation in terms of shorter hospital stays6, lower chance of developmental delay31, improved body composition, and improved visual development.32

How do I get DHA into my diet?

A mother’s diet has a significant impact on how much DHA her fetus can accumulate, and how much DHA her baby has at birth. Pregnant women who eat fish, or who take fish or algae oil supplements, give birth to infants with significantly higher DHA levels, compared to infants born to mothers who don’t consume preformed DHA sources.33 Further, these higher DHA levels at birth are sustained in the infant throughout the first few months of life, as opposed to the decline in infant DHA status that typically occurs.33 Taking DHA supplements6,34,35or regularly eating fatty fish36,37 during pregnancy significantly increases DHA in the newborn and in breastmilk.

Safety of DHA during Pregnancy

Of course, the primary concern with increasing DHA intake is whether there is a safety risk to your unborn baby, or to you. The quick answer is: DHA supplementation during pregnancy is very safe.6,38

Now that you know why DHA is important during pregnancy, you know what to do: Eat fish. Take a supplement. Spread the word to random pregnant women on the street. It’ll be brilliant! Just like you.

Sharon Matheny, PhD is Manager of Nutrition Science Communications for Nordic Naturals. She holds a doctorate in Cell and Molecular Biology, with specializations in cancer cell signaling and molecular neuroscience. After a career in biotechnology developing molecular diagnostics, she has found her calling in bringing evidence-based nutrition and health science information to the general public and health professionals.

Adiposity: The degree or level of obesity.

Body Mass Index (BMI): The ‘thinness’ or ‘thickness’ of a person based on their height and weight. Calculated by dividing weight by the square of height (kg/m2). BMI is calculated slightly differently in children and teens.39

Interventional study: A type of clinical study where participants are provided with a substance or behavioral change to examine the effect on specific health outcomes.

Observational study: A type of study where no attempts to affect the outcome are made, but individuals are observed, or certain outcomes are measured.

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