Replied by Ted (Bangkok, Thailand)
Generally the most damage that can be done to a baby is when the mother becomes malnourished, the mother suffers acidosis (acidic urine pH of below 7), electrolytes become imbalance such as not having enough magnesium, causing cramps.
Generally speaking taking some prenatal vitamins which have vitamin B complex helps. A condition of acidosis can be checked to see if urine pH is within normal parameters, and if not it can be ascertained bicarbonate levels of the body is low.
Hence, if the body is low on bicarbonate and a heart burn is indicated, then if it helps the mother from her sickness, taking them would at least allow the body to achieve normal pH parameters.
At the very least, baking soda should reduce nausea and vomiting. Assuming baking soda is not use and the body undergoes acidosis, bringing on vomiting from acidosis whenever the body tries to throw off excess acid may actually disrupt the body's delicate electrolyte balance more.
Hence some electrolyte drinks may be helpful too that contains potassium and in some rare cases, a good electrolyte drinks may also have the needed magnesium too.