Huh... well that's a new one on me. I've never heard of that- it's the folic acid (in prenatals) that helps protect against neural tube defects... so I'm thankful to hear they recommend you continue that... I wonder why not everything else in the pre-natal vitamin? Mixing with the LDA? Not a clue!
If you're not comfortable you could always give a call and ask for a clearer explanation.
2008-Our Baby Girl, PTL born too early at 30w6d, Fought so hard... Forever Loved & Missed
2010- Lil' Bro, Pre-E at 29 weeks... Induced at 36w6d, Born 37w
2012- Lil' Sis, Super-imposed pre-e at 25 weeks, PTL & GD at 35 weeks, Evicted 36w