 Omega 3 fish oil supplements are one of the most popular or commonly taken supplements in the world. Fish oil capsules are very fragile. Exposure to light, air and to being warmed leads to them becoming oxidised or off. Because we realised that they might go off, we tested products on the New Zealand market and what we found was that almost all of those products were oxidised above recommended levels. There have been studies from around the world that have shown the same thing from Norway, from South Africa and North America. We also realised that oils that have become oxidised might have different effects on the body and those effects could be harmful. Pregnancy is a really special time because the fetus is more sensitive to chemicals and other things that might affect the health of mum or baby. And we also know that around 1 in 10 pregnant women take fish oil, so it's really important for us to know if it might have harmful effects. So in our later study we looked at rats that were pregnant and we gave them fish oil during pregnancy or an oxidised fish oil, a fish oil that had gone off. What we found was that at the end of pregnancy when the rats were born in the group where mum had had an oxidised fish oil, nearly a third of the babies died. We were surprised to see such a strong effect of the oxidised oil. Almost a third of newborn rats died after their mothers were fed oxidised or off fish oil during pregnancy. However, unoxidised fish oil did not have this effect. Studies from New Zealand and overseas have shown that fish oil supplements are frequently oxidised when sold. We can't apply the findings from our study directly to humans, but there is some cause for caution. It's not possible to simply translate the findings from our study directly into human pregnancy. We gave a higher dose of fish oil than women would usually take in pregnancy and the oil was also more oxidised. The health risks of oxidised fish oil to the unborn baby at present are unknown. It is not possible to know whether fish oil supplements that are purchased are oxidised at the point of sale. Thus we believe it is wise that pregnant women do not take fish oil supplements until the risks are better understood. At present we would recommend eating fresh fish for omega-3 intake.