Fluid intake is important during pregnancy, and pregnant women should drink about 8 glasses of fluid daily. Water is the best fluid to drink, for it gets right to work in your body lubricating every part of you. Sufficient water intake can keep you from becoming constipated, keep your skin from being too dry, and flush toxins and waste products from your body efficiently.
Soda doesn't need to be totally eliminated from your diet during pregnancy, but soda has some qualities that aren't so good in pregnancy. Regular soda is filled with sugar and empty calories those are always a problem in pregnancy. Diet soda is filled with aspartame or other artificial sweeteners, and it's not a good idea to overload on those in pregnancy either. Some clinicians are worried about the calcium depletion that is possible with the ingestion of a lot of phosphate, as is found in soda. Also, many sodas contain caffeine, which should be ingested very sparingly (if at all) during pregnancy. There are no studies showing that artificial sweeteners harm fetuses, but just as you avoid other substances during pregnancy, these additives shouldn't be a routine part of your diet in pregnancy either, just to be safe. So, if you absolutely love soda, having an occasional one isn't going to hurt you, but you're far better off drinking water and fruit juices during pregnancy.