What is dehydration?

Dehydration is an insufficient amount of water in the body. Either insufficient drinking or excessive water loss from the body can lead to dehydration.

Is dehydration in pregnancy a serious condition?

Dehydration can be a mild nuisance or a life-threatening condition for both the mother and the baby.

What are common causes of dehydration in pregnancy?

A pregnant woman can become dehydrated from the same reasons as anyone other. Main causes include:

  • Insufficient drinking
  • Excessive sweating, mainly due to high ambient temperature
  • Excessive urination
  • Severe or prolonged diarrhea
  • Severe or repeated vomiting
  • Prolonged hyperventilation, for example due to anxiety and associated chronic hyperventilation syndrome.

Morning Sickness

Morning sickness can prevent a woman to eat and drink enough. In severe morning sickness called hyperemesis gravidarum, a woman can additionally lose a lot of fluid by repeated vomiting and is therefore at high risk for severe dehydration that requires admission to hospital and intravenous fluid replacement.

Symptoms and Signs of Dehydration in Pregnancy


Symptoms: Thirst (not always), slight anxiety, slightly decreased frequency of urination Signs: Slightly increased heart rate.


Symptoms: Severe thirst (not always), dry mouth, decreased frequency of urination, dark yellow or tea-colored urine, tiredness, dizziness, headache, nausea, constipation.

Signs: Increased heart rate, prolonged skin recoil after pinch and release (up to 2 seconds).


Nausea and vomiting, usually in the first trimester (but sometimes even in the third trimester), are the main causes of severe dehydration in pregnancy.

Possible symptoms:

  • Extreme thirst, but the woman may feel no thirst due to nausea
  • Dry mouth and chapped lips
  • Low amount or dark, tea-colored urine or no urine at all
  • Nausea, vomiting, abdominal pain and cramps
  • Severe headache
  • Exhaustion
  • Fainting
  • Confusion
  • Coma.


  • Very increased heart rate, possibly greater than 140/min
  • Increased frequency of breathing
  • Sunken eyes
  • Pale, cool, dry skin
  • Prolonged skin recoil (> 2 seconds)
  • Low blood pressure (a late sign of dehydration, which may speak for hypovolemic shock)
  • Severe dehydration caused by severe vomiting can be associated with nutrient deficiencies may result in death.

Effects of Dehydration on the Baby

Severe dehydration can affect the baby [1,2,4]:

  • Decreased amount of amniotic fluid (oligohydramnios), which can cause that the baby lies directly on the uterus can lead to arm and leg deformities or other birth defects.
  • Severe dehydration may trigger contractions, premature labour or miscarriage.

How much water should a pregnant woman drink to prevent dehydration?

According to the U.S. Institute of Medicine (IOM), the Adequate Intake (AI) for water during pregnancy is 3 liters 5. Adequate intake means amount of water from both foods and beverages that would provide adequate hydration for most pregnant women. But a woman may need less or more than this amount of depending on how much of water she loses. You probably drink enough when:

  • Your body weight has not dropped suddenly (hours/few days) from your usual pregnancy weight
  • You excrete at least about 300 mL of clear or bright yellow urine in the morning
  • The skin on the back of your hand recoils instantly when you pinch and release it.

Treatment of MILD or MODERATE Dehydration in Pregnancy

When you are mildly or moderately dehydrated you can replace the lost fluid by drinking more water. For every kilogram of lost weight you drink about 1.5 liters fluid (to cover the missing amount of water and the current loses from the urine).

  • Appropriate beverages to treat dehydration in pregnancy: water, herbal tea, decaffeinated coffee.
  • Less appropriate beverages, but still acceptable: fruit juices, soft drinks and other drinks high in sugar, sport drinks, clear soups and milk (may be harder to drink in nausea or contribute to weight gain).
  • Inappropriate beverages: any alcoholic beverage.

It is not clear if caffeine is harmful for the developing baby, but most doctors advise against drinking caffeinated beverages (regular coffee, tea, cola, energy drinks) during pregnancy.

When to go to hospital?

  • When you can not eat and drink anything in any given day, no matter how mildly dehydrated you think you are.
  • When you have signs and symptoms of moderate to severe dehydration: you have lost 5% or more body weight in few hours/days, you excrete dark urine.

Treatment of SEVERE Dehydration in Pregnancy

Nausea and vomiting are the main causes of severe dehydration in pregnancy. Severe dehydration is usually treated in a hospital with infusion of fluids, such as 0.9% solution of sodium chloride into a vein (intravenous infusion). Treatment of nausea and vomiting may be necessary at the same time.

Are ketones in urine a sign of dehydration?

Ketones in the urine of pregnant women is usually a sign of low carbohydrate diet or fasting due to nausea, or gestational diabetes. Dehydration can cause false positive results for urinary ketones [3].

  1. Maternal dehydration and oligohydramnios  (americanpregnancy.org)
  2. Complications of hyperemesis gravidarum  (babycenter.com)
  3. Ketones in urine in pregnancy  (patient.co.uk)
  4. Dehydration and oligohydramnios  (americanpregnancy.org)
  5. Dietary reference intakes for water and electrolytes  (iom.edu) [/ref]