What Causes Dehydration During Pregnancy

Physical changes in the body during pregnancy can cause dehydration. You need to drink more water when you’re pregnant to maintain your health and support fetal development.

Causes of Dehydration During Pregnancy

During pregnancy, your body undergoes changes that increase its need for water. You require more water than before and lose more throughout the day. Dehydration happens when you lose more water than you take in.

Factors increasing dehydration risk during pregnancy include:1

• Blood volume increases: Your body needs more blood flow during pregnancy, increasing blood volume by 30% to 45%. This requires more water to maintain balance.
• Urinary system changes: The kidneys usually become slightly enlarged during pregnancy. This leads to changes in the urinary system that cause the body to lose more water.
• Respiratory system changes: The increased demands on a pregnant person’s body cause them to breathe more. Each time you exhale, your body loses water through your breath.
• Increased metabolism: Pregnancy causes the adrenal and thyroid functions in the body to become slightly hyperactive. This leads to an increased metabolism and more sweating. When the body loses water through sweat, the risk of dehydration increases.
• Increased nutritional needs: A pregnant person requires an extra 300 calories daily, rising to 450 additional daily calories in late pregnancy. Eating more means that a person needs to drink more to support digestion and prevent constipation.
• Morning sickness: Nausea and vomiting are common during pregnancy. Because vomiting from morning sickness causes fluid loss, it increases the risk of dehydration. People who are nauseated throughout the day also may have trouble drinking enough water.2

Symptoms of Pregnancy Dehydration: How to Tell It is not uncommon to become mildly dehydrated during pregnancy. Early symptoms of dehydration may include:3

• Constipation
• Dark yellow urine
• Decreased urination
• Dry mouth and chapped lips
• Feeling thirsty
• Headaches

If your body does not receive enough water when mildly dehydrated, further symptoms may include fatigue, dizziness, feeling overheated, and having Braxton Hicks contractions (tightening and release of the uterus not due to labor contractions).4