Any brand is going to be OK. You may want to take calcium as well as they go hand in hand and can be found in a vitamin together.
I take a vitamin d supplement as well!..it's a no name brand, as long as you're taking one you'll be fine! I got mine at sprouts, I know they have good vitamins :)
I'm in australia and take ostiovit. I also take vitamin b12 and folic acid to get my levels up and also help to reduce any side effects if the vitamin d. Too much vit d can cause calcium deposits (u need to have a lot for that to happen) but the extra folic acid and vit b12 help.
Just go sit outside for an hour a day.
I like the viactiv chews ... they have the vitamin d and the calcuim you need while your pregnant
outside is the best way for your body to get and absorb vit d for just 10-15 min per day in direct sunlight, if your skin is darker you need abit longer 20-min to 1/2 hr, just sit out on your patio and have a drink or go for a walk