Vitamins CAN cause sickness, therefore leading to dehydration, but there are so many alternatives, taking them before bed, taking them with or without a meal, taking gummy versions, etc. I really would've found a different way, because like anniebrooke said, the folic acid, among many other things, is important. There are, and were plenty of women that never took vitamins and their baby was fine, but personally, I don't miss a day of taking my vitamins. I'm sure your LO is just fine!