Fish oil supplementation

Question: Does supplementation with fish oil (omega-3 or n-3 fatty acids) during pregnancy affect placental function and fetal growth?

Answer: Oh yes. We studied placental metabolism in tissue collected from randomized controlled trial of women supplemented with fish oil or placebo from early second trimester to term. Fish oil supplementation decreased placental lipid content by 30% (see Figure) and impaired the placenta’s ability to store lipids (esterification).

Surprise: Babies born to the women randomized to fish oil supplements were larger, which could mean that placental lipid storage limits the amount of fat delivered to the baby.

So what: Many women supplement with fish oil during pregnancy, for its purported anti-inflammatory and plasma lipid lowering effects. However, we do not understand how these supplements alter placental function, thereby affecting the fetus.

Follow-up studies: We subsequently found with collaborators in Hawaii that placental lipid content in mothers who naturally have a higher fish intake (and 10-fold higher omega-3 fatty acid levels at birth) was lower compared to our Cleveland cohort (naturally lower fish intake). Thus dietary fish intake, associated with high maternal omega-3 fatty acid levels, may also lower placental lipid content similarly to fish oil supplements. Interestingly, maternal obesity was not associated with placental lipid accumulation among patients in Hawaii.


Calabuig-Navarro et al. 2016 Effect of ω-3 supplementation on placental lipid metabolism in overweight and obese women.

Alvarado et al. 2018 Maternal obesity is not associated with placental lipid accumulation in women with high omega-3 fatty acid levels.