OKy doky, have done some fishing, and according to the US FDA (Food and Drug Authority) levels up to 10,000IU per day are safe during pregnancy. The Beta Carotene form of Vitamin A found in vegetables etc. is safer than the Vitamin A found in meat products such as liver, so pregnant womeb are advised to limit, or avoid, eating meats high in Vitamin A.
The paper is here
http://pregnancy.about.com/gi/dynamic/offsite.htm?zi=1/XJ&sdn=pregnancy&zu=http%3A%2F%2Fvm.cfsan.fda.gov%2F%7Edms%2Ftpvita.html
Also, I have done some searching on Prenatal vits, and 5000IU seems to be the standard level.
I am taking a pregnancy multivit made by Microgenics. I tok Thompsons Pregnacare when I was pregnant with Maya, and planned to do the same this time, but the lady in Health2000 recommended the Microgenics one as being better. Elevit also has a good reputation.
Hope this helps. I will put together some solid info on prenatal vits and post it on OhBaby! soon, and I will post the link here for you once I get it done.