You mentioned WAPF, but said you didn't find much about supplementing. Well here it is:

WAPF: Vitamins for Fetal Development: Conception to Birth

Folate for neural tube defects is only important in the first trimester. After that the neural tube is closed and all the folate supplementation in the world won't change anything. You can try to make sure you get a good amount from food, but you may or may not have morning sickness and it may or may not be severe, so it's not something you can definitely count on. I personally had really bad morning sickness and I could hardly even keep down food. I felt that taking a vitamin was a good idea in my case. Even though I don't usually take supplements for myself, I did not want to gamble on the health of my baby. Multivitamins are kinda hard on the tummy, but I tried to make myself take at least half a pill with some folate-containing food every day. After the morning sickness went away, I started taking the full pill plus extra vitamin D and fish oil. I had a really healthy pregnancy and an uncomplicated unmedicated birth and my little girl is 4 months old now and doing great. :)

note: I was paleo prior to conceiving, but was not paleo during pregnancy - was more WAPF-ish

Before getting pregnant I was not taking any supplements - when we found out I was pregnant I started taking a liquid maternity supplement recommended to me by my naturopath. I felt it was really important to supplement because I had morning sickness so bad that I wasn't eating anything. The only problem was the supplement was making me even more nauseous than I already was - so I only took it at night in a half dose until my nausea wore off (which wasn't until 24 weeks - not very typical).

After that I just ate a really balanced paleo-diet (I added milk products - because I was craving them). I think the most important thing is to listen to your body while you are pregnant. Towards the end of my pregnancy I could feel myself becoming anemic (even with all the meat I was eating) so I added Floradix, which is a natural iron supplement, to my daily routine and it really helped!

I would recommend talking to a naturopath about more natural supplements.

I have a wonderfully healthy walking and talking 18 month old now

Most women get sufficient folate to prevent neural tube defects on pretty much any diet. The paleo diet, being high in vegetables, should be especially good in this respect.

Some women naturally absorb less folate. This is likely to not be known until after she conceives a baby with a neural tube defect, which is why it's recommended that all women who may conceive take folate supplements. Alcohol and some medications such as antiepileptic medication can also interfere with folate absorption, increasing the risk of neural tube defects without folate supplementation.

Folate supplementation is most important for several months pre-conception as a lot of neural tube development takes place before many women realize they are pregnant, and because it may take a while to replenish the body's stores if they're low to begin with.

So, long story short, chances are your baby will be perfectly fine without supplementation, especially if you're eating your green leafy vegetables. However, supplementation is unlikely to hurt, and may help if you're in the small segment of the population that can't adequately absorb folate.

Do not forget Vit D3 supplementation for the mother as it assists the body to assimilate calcium which makes for strong bones in the fetus. The Vitamin D Council has received letters from mothers that have been accused of baby child abuse because of broken bones in the infant. Some infants have been taken away by Child Protective Services. What a nightmare for any family....especially when they learn simple supplementation with D3 would have prevented the brittle bones in the newborn. Sometimes the delivery process of a weak boned baby is enough to break bones.

Vit D3 supplementation is so very important during gestation for the development of the fetus. Believe it or not, there are children still born in the US that have rickets. Thus the absurd recommendation from the Institute of Medicine (IOM) to supplement with 400IU Vit D3...which will barely prevent rickets. WAPF recommends 2000IU but most of us take more.

Do some more research along the Weston Price Traditional Diet lines. Many Traditional cultures have special foods for before, during, and after pregnancy. Sorry I don't have much more on this myself, but I know the info is out there.