Fish oil supplementation in pregnancy

Updated: May 16, 2019



"All of the omega-3 and omega-6 fatty acids accumulated by the fetus must ultimately be derived from the mother by placental transfer" Greenberg et al. 2008

Two well-known omega-3 essential fatty acids are EPA and DHA. These two oils are termed 'essential' because they cannot be synthesised by the body. This means we can only get them from our diets by consuming seafoods, algae or certain plant-based oils including flax, chia, or hemp, or through supplementation. These oils are essential for neurodevelopment and function, hormone production, immune function, and are essential for maintaining the structure of every single cell in the body. Perinatal (that is intake before pregnancy) and natal (during pregnancy) intake of omega-3 essential fatty acids is beneficial for fetal and early childhood development.


Benefits of omega-3 fatty acids during pregnancy:


- DHA is important for fetal neurodevelopment including motor skills


- DHA is essential for development of the brain and eyes during gestation and up to 18 months of life


- EPA and DHA reduce the risk of allergies in childhood


- Adequate EPA status during pregnancy reduced pre-term labour and preeclampsia risk


- Greater language and visual and motor skills in early childhood



Getting omega-3 fatty acids during pregnancy


Research shows that during the 3rd trimester, 50 - 70 mg of DHA are used by the fetus per day and dietary requirements is likely increased during pregnancy but how should we get this increased amount of omega-3s? What about mercury?


Despite the evidence for omega-3 fatty acids in pregnancy research also indicates that the consumption of fish in pregnancy should be limited due to risk of methylmercury contamination. As mercury is toxic to a developing brain and nervous system the recommended limit of fish in pregnancy women is two servings of low-mercy fish weekly.


This means two things. 1.) A healthy pregnant woman with no existing heavy metal accumulation or detoxification issues can eat to serves of low-mercury fish and/or 2.) supplement EPA and DHA.



How to choose fish wisely:


- Avoid large fish that are high on the food chain e.g. shark/flake, swordfish, king mackerel, orange roughy some types of bluefin tuna,


- Choose smaller fish e.g. sardines, herring/tommy ruff, anchovies


- Choose other seafood e.g. prawns, mussels, pollock, squid, ocean perch, coorong mullet


- Light canned tuna is sometimes recommended as a better option however this could become problematic if consumption of fish is from BPA-lined tins. See here to read about BPA / plastics and hormone disruption.



Choosing a fish oil supplement wisely:


NOT ALL SUPPLEMENTS ARE EQUAL - This is important to note.


- You get what you pay for and not all companies produce the same quality of product.


- Purity: Look for quality assured brands that use high quality heavy metal and other contaminant testing. Talk to your health professional about choosing a reputable brand.


- Freshness: Fish oils (like all other oils) are subject to going rancid if exposed to heat, light, and air for too long. Rancid oils are more harmful than helpful and cause inflammation. Never take out of date oils, always store in an airtight container and in the fridge if liquid.



Omega-3 from plant sources:


Variety is great and getting your fatty acids from plant sources as well as marine sources is beneficial for health. Not all oils are equal however and other nutrients such as B6, zinc, magnesium, and vitamin C are required to convert plant oils including ALA to EPA and DHA. The best way to ensure this is to eat a variety of foods including fresh produce, eggs, and lean meats in moderation.


Some plant sources high in healthy fats include:


- flaxseeds

- avocado

- olive oil

- hemp seeds

- chia seeds

- microalgae such as spirulina and chlorella.


It should be noted that EPA and DHA content in these food sources as lower than that of marine based foods like fish and as mentioned above some of the oils will also require conversion with the help of other nutrients. There is, undeniably, plenty of evidence for plant-based eating and the consumption of plant sources of omega-3 is highly recommended for many aspects of health not just in pregnancy.














Greenberg JA, Bell SJ, and Ausdal WV, 2008, 'Omega-3 Fatty Acid Supplementation During Pregnancy, Reviews in Obstetrics and Gynecology, Vol 1, no 4 pp162-169

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