Do you recommend fish oil or omega 3 for pregnant woman? if yes, what king and what dose?

Not necessarily: You must be guided by your OB for supplements in pregnancy.

Yes: Yes this can be very helpful for developing baby particularly dha for brain and eye development. Look for a high quality source that screens for heavy metals (mercury) and pcbs which are other pollutants. Krill oil, which is lower down on the food chain is a great option as those toxins bioaccumulate.