If Vitamin C is taken in mega doses during pregnancy, is can theoretically have a negative effect on the pregnancy and the developing baby.
Vitamin C is perfect for keeping the immune system healthy. When pregnant, the RDA is 85 mg per day, but Vitamin C supplementation is safe up to 2,000 mg. All Vitamin C supplements should be approved by the obstetrician before adding the supplement to the daily Vitamin regime.
Some people use multivitamins that contain very high amounts of vitamin C. These are not considered safe during pregnancy as they will contain too much Vitamin C. The best vitamin supplement during pregnancy is one that's specifically designed for pregnant women and contains just the right amount of vitamins.
If mom gets dehydrated during pregnancy, the amniotic fluid level will decrease. The amniotic fluid is the lifeline for baby. Without this fluid, the baby will not gestate to term. Dehydration can also cause nausea which can lead to vomiting and even worse dehydration.
If mom is feeling cramps, gas, bloating and has diarrhea soon after taking Vitamin C, the obstetrician needs to be notified and the Vitamin C stopped until the doctor advises otherwise.