I have a golden retriever who is approx 21 days into her first pregnancy, she was mated 3 times. I'm interested in giving her folic acid suppliment as I believe it could be beneficial in reducing clef pallet and spinal problems. Could anybody tell me if they have already tried this and would they advise me to give it to her.

I know this is well researched in humans, and needs to be used pre-conception and up to 12 weeks while the spinal nerves are forming. Not sure with dogs though, but don't see why it shouldn't have same effect. You'd need to check dosage though. Maybe your vet would know.
Lorna