Yes. It is possible to drink too much water when pregnant. This can lead to a condition called hyponatremia, which is characterized by low levels of sodium in the blood. Symptoms of hyponatremia include headache, nausea, vomiting, fatigue, muscle weakness and cramps. In severe cases, it can cause seizures and coma. If you are pregnant and think you may be drinking too much water, contact your healthcare provider immediately.