My doctor has said that since the WHO's website doesn't mention that DHA (Docosahexaenoic acid, an omega-3 fatty acid) intake is compulsory, she won't be talking about it.

I am referring to the vegetarian sources of DHA such as algae.

At what month of pregnancy should DHA intake be started so that it actually helps the brain development of the infant?

  • Please note that our FAQ excludes medical advice, and I'm concerned that your question is bordering on that. Apr 5, 2013 at 10:14
  • @TorbenGundtofte-Bruun Well, I read the FAQ, and it says that health topics are on topic. As an answer I am not asking for "effects of DHA". I am asking at what time does infant brain actually start taking advantage of these kind of supplements. Apr 5, 2013 at 11:02
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    I would agree with @TorbenGundtofte-Bruun, this is asking nutrition, not health advice and is our of scope for the forum. I don't think many on this forum would be able to answer your question anyway.
    – GdD
    Apr 5, 2013 at 13:04
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    Pregnancy questions are considered on topic, and health advice directly relating to pregnancy has some support. The medical aspect is a little greyer, but I'm leaning on the side of it being on-topic (this isn't about a disease or illness; its about maximizing possible benefits for the baby).
    – user420
    Apr 5, 2013 at 15:41

2 Answers 2


While the benefits of DHA are disputed, it appears that you can start as early as week 18:

In the double-blind study, “Prenatal Docosahexaenoic Acid Supplementation and Infant Morbidity: Randomized Controlled Trial,” published in the September 2011 issue of Pediatrics (published online Aug. 1), pregnant women in Mexico were supplemented daily with 400 mg of DHA or placebo from 18 to 22 weeks gestation through childbirth.

Note that a study in 2010 found no difference in the rate of post-partum depression or cognitive development of the children.

However, this result apparently conflicts with an earlier study from 2003 (which also started the pregnant mothers on supplements at week 18).

  • Those studies only compared starting at week 18 with not starting at all, in order to capture the "last half of the pregnancy." You can't really draw conclusions about the most beneficial timing from those results. Apr 5, 2013 at 16:42
  • I'm not sure there's such a thing as "most beneficial timing" (especially given the conflicting results of the studies). My intent was more "it appears safe to start at 18 weeks", rather than "for best results, start at 18 weeks". I'm not sure why waiting beyond that would give better results, but I suppose it is possible.
    – user420
    Apr 5, 2013 at 16:51
  • I agree waiting beyond 18 weeks is unlikely to give better results, but a lot of other nutritional supplements have been proven to give better results when started earlier, even before becoming pregnant. I don't see anywhere questioning the safety of DHA, just the efficacy. Apr 5, 2013 at 18:11

DHA and EPA are long-chain omega-3 fatty acids which cannot be synthesized by the human body and thus must be ingested either through capsules (which is usually fish oil) or through the foods that we eat. They typically are found together and work both in conjunction with each other and independently of each other to support proper neurological, immunological, and cardiovascular development. Since neither DHA or EPA can be created by our bodies on their own, it is VERY easy to become deficient in these omega-3s if you are not consuming it on a regular basis. The most prolific source of DHA/EPA is in fish oil or algae, so unless you are eating either of these two things on a regular basis, you could all ready be deficient.

A woman's stores of DHA/EPA become depleted as the developing fetus begins to use the mother's stored DHA/EPA during its neurological development. Brain development really kicks into high gear in the 3rd trimester (beginning at 28 weeks), so more and more DHA/EPA will be transferred from mother to baby to support brain, eye, immune, and nervous system development. HOWEVER depending on one's diet, it is very easy to be deficient in this nutrient before one even gets pregnant. Like folic acid, it is usually best to begin supplementing before pregnancy so that you can all ready have plenty of stored DHA/EPA/folic acid in place before you actually conceive. Furthermore, breastfeeding will further deplete any stored DHA/EPA you may have as both are known components of human breastmilk so continuing supplementation after birth is important as well.

In terms of cognitive development, the jury's still out as to the effect on the fetus with omega-3 supplementation. By that I mean to say that there is no evidence to suggest that a child's cognitive development is significantly changed by taking a DHA supplement during pregnancy (though it stands to reason that a fetus who was significantly deprived of DHA/EPA during its growth would show delayed cognitive development). And your ob/gyn is correct, the WHO does not currently give a recommendation for marine oil supplementation during pregnancy, but there is some evidence to suggest that DHA can help prolong a pregnancy thus increasing gestational age in the baby.

Americanpregnancy.org recommends that a high-quality DHA/EPA supplement be taken before, throughout, and after pregnancy. Fish oil is the ideal source of this, though algae is also acceptable. So...if you follow those recommendations you should probably start as soon as possible. According to this commentary from the WHO, "Overall, the three meta-analyses show that supplementation with marine oil or n-3 LCPUFA is safe in pregnancy and generally well-tolerated".

  • Just wanted to add a note about the comment that "fish oil is the ideal source." Our OB specifically ask that we avoid DHA derived from fish oil and that we limit fish consumption to 3x per week or less, due to concerns about mercury toxicity (which she also stated has more proof of being a problem than DHA/EPA has proof of providing benefit). Algae-based DHA avoids these concerns, so that's the route we go. Nov 26, 2014 at 15:01

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