Fish oil got me through my pregnancy and the PPD that followed. I asked many doctors about what brand to buy and I was told repeatively that it did not matter and they did not have mercury in them. They told me that however fish oil is made, it does not have mercury. This was by several different peds and obs.

FWIW, I generally take the costco brand. It has no effect on my breath and it works very well. I have generally been very impressed with the kirkland brand and the extents to which costco goes to have quality products. (Now, if only we could get them to sell non-CAFO beef.) :p