Fish oils are wonderful, I wish I had known about them with my previous pregnancies. I'm currently 27 weeks pregnant with # 4 and take Neevo DHA, it's prescribed to me by my OB and has fish oils already in it. My nurse also said it's great for absorbtion. Hopefully you can get something like Neevo, they've been great. My sister also takes them with her pregnancy and LOVES them too.
You can fine a lot of info online regarding the benefits of fish oil for the developing baby, it's amazing! It can also help with depression & post partum depression, etc.
P.S. Be careful which ones you buy OTC, ask your pharmacist what they recommend. Before I had my first OB appointment, I picked up some fish oil pills at the dollar general, they were HORRIBLE! Gave me bad indigestion and I kept burping fish, ugghhhh. The Neevo vitmains have never done that to me, but you won't be able to get those until your appt. so for now, just ask a pharmacist what they think is best for the pregnant body.
Good luck and congrats!!