Taking DHA-enriched fish oils during the second half of pregnancy does not lower the risk of developing preeclampsia or gestational diabetes, researchers from Adelaide University, Australia, reported in the American Journal of Clinical Nutrition.

The authors explained that experts have long been unsure about what the effect of increasing the intake of fish oils – n-3 long-chain PUFA (LCPUFA) – might be in reducing pregnancy complications, such as preeclampsia and gestational diabetes mellitus.

Maria Makrides and team set out to determine whether giving pregnant women n-3 LCPUFA supplements during pregnancy might reduce the risk of preeclampsia and gestational diabetes.

They also wanted to determine whether n-3 LCPUFA supplementation might have an impact on reducing the risk of perinatal complications. Perinatal refers to the period immediately before and after childbirth occurs.

DOMInO was a multicenter, randomized, double-blind control trial, involving 2,399 women who were less than 21 weeks pregnant at the start of the trial. They were randomly selected to receive either DHA-enriched fish oil (800 mg per day) or a vegetable capsule with no DHA in it. They took their capsule each day until birth.

They assessed whether the participants developed gestational diabetes or preeclampsia through a blinded audit of medical records. They also assessed birth outcomes and prenatal complications.

They found that:

  • 8% of those in the DHA-enriched fish oil group developed preeclampsia or gestational diabetes

  • 5% of those in the vegetable capsule with no DHA group developed preeclampsia or gestational diabetes

  • Babies’ birth weight, head circumference, and body length – there was no significant difference between the two groups

  • There were 12 perinatal deaths in the DHA-enriched fish oil group, compared to 3 in the other group

  • There were 5 neonatal convulsion in the DHA-enriched fish oil group, compared to 0 in the other group

In an Abstract in the same journal, the authors concluded:

“DHA supplementation of 800 mg/d in the second half of pregnancy does not reduce the risk of GDM or preeclampsia. Whether supplementation reduces the risk of perinatal death and neonatal convulsions requires further investigation.”

Fish oils come from the tissues of oily fish, such as salmon, mackerel and halibut. The oils contain omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) – these are precursors of some eicosanoids that experts say reduce inflammation throughout the body, and have other health benefits.

Oily fish to not produce omega-3 fatty acids, they accumulate them by either preying on other fish that have accumulated omega-3 fatty acids or by consuming microalgae.

Some predatory fish, such as swordfish, tilefish and sharks are high in omega-3 fatty acids. However, as they are at the top of the food chain, they have usually accumulated substances through biomagnifications which are toxic to humans. They may be high in mercury, dioxin, PCBs and chlordane.

Experts say that fish oils may help protect humans from developing several diseases and conditions, or alleviate symptoms, such as many cancers, cardiovascular diseases, depression, anxiety, lower assault rates in prisons, Alzheimer’s disease, Parkinson’s disease, and psoriasis. In some examples mentioned here, studies have produced promising findings, but further research is required.

People receiving chemotherapy drugs are advised not to take fish oils because they can render the drugs ineffective. (Link to article)

Salmon 01
Illustration of various types of Salmon. Salmon is rich in fish oils

Written by Christian Nordqvist