Dehydrated during pregnancy? Here’s why and how to fix it

From the desk of
Nicki Violetti
ScienceDehydrated during pregnancy? Here’s why and how to fix it

If you’re worried about becoming dehydrated during pregnancy, you’re not worried for nothing. Pregnant women need more water for amniotic fluid, placental function, and the maintenance of blood volume.

Combine that with the increased sweat, urinary, and respiratory water losses of pregnancy and you have a formula for dehydration. With dehydration, unfortunately, comes risks for mother and child.

I’m not suggesting pregnant ladies reach for a water bottle every five minutes. That’s risky too. “Drinking water is risky? Come on, Nicki.” I know it sounds strange at first, but drinking too much water can deplete sodium levels. Low sodium, in turn, can lead to undesirable symptoms and sad complications during this important time.

Low sodium also impacts breastfeeding. I didn’t know much about sodium when I gave birth to Zoe (my first child), but I believe a lack of salt impaired my milk supply. It was frustrating.

Since then, I’ve connected with many amazing moms (and moms to be) to help them stay healthy and hydrated. The truth is, hydration isn’t just about preventing dehydration—it’s about getting enough electrolytes too.

Today I want to talk about what causes dehydration during pregnancy, but I also want to talk about rehydrating the right way. (Hint: Drinking water is only half of it!) Let’s go.

What Is Dehydration?

When you lose more water than you consume, you’re said to be dehydrated. That’s the classic definition. You lose water through sweat, urine, breathing, and feces—and you take it in through fluids and foods. Ideally, you want these sides roughly balanced.

Generally, they are roughly balanced. Contrary to popular belief, dehydration is rare in the average healthy person.

Why? Because the human body is a snazzy fluid balancing machine. If you drink too much water, you excrete more fluids. And if you don’t drink enough, you excrete fewer fluids. Plus, you get thirsty. Assuming you don’t ignore the urge, thirst is awesome for preventing dehydration.

But certain situations (like pregnancy) may increase the risk of net water loss. How do you know if you’re dehydrated? Look for the following dehydration symptoms while pregnant:

  • Dark urine
  • Dry mouth or excessive thirst
  • Dry skin or dry lips
  • Lower urinary volume
  • Constipation
  • Fatigue
  • Lower blood pressure
  • Dizziness or fainting
  • Nausea
  • Rapid heartbeat (tachycardia)

Many of these symptoms are nonspecific, but if you’re thirsty and your pee is the color of deep amber—you’re probably dehydrated. Let’s talk more about pregnancy now.

What Causes Dehydration During Pregnancy?

The short answer is that pregnancy raises fluid needs. If those needs aren’t met, dehydration will result.

The longer answer entails frolicking through the physiology to see what exactly raises fluid requirements during pregnancy. I hope you like lists as much as I do.

8 Reasons Why Pregnant Women Need More Fluids

  1. The amniotic sac is a fluid-filled bag that holds the fetus in the womb. Those fluids must come from somewhere!
  2. The placenta (an organ on the edge of the uterus) requires water to pass nutrients to the growing fetus.
  3. Blood volume slowly increases throughout gestation, peaking at 32 to 34 weeks in.
  4. During pregnancy, the kidneys grow to filter a higher volume of blood. As a result, urinary volume increases, especially when lying down at night.
  5. Pregnant women breathe more rapidly and take more air into their lungs. This increases respiratory water losses.
  6. Being pregnant makes you sweat more. (Oh, how fondly I remember this!) Why? Because the thyroid ramps up, metabolism ramps up, and more blood rushes to the skin.
  7. Pregnant women need about 500 more calories per day, and digesting those extra calories requires extra water.
  8. Hormonal changes also influence fluid balance. For instance, the surge of prolactin seven weeks into pregnancy helps prepare the mammary glands for milk production, and making milk requires fluids.

Many women don’t sufficiently compensate for all these water drains. What are the risks of not getting enough fluids?

Risks of Being Dehydrated During Pregnancy

I already covered the short-term risks of dehydration: fatigue, headaches, dry skin, and other symptoms. Inadequate fluid intake, however, appears to carry longer term risks.

I say “appears to carry” because the evidence isn’t exactly grade-A. Much of the data comes from terribly-unreliable fluid intake surveys in uncontrolled populations.

With that in mind, some research has found a link between dehydration and birth weight. In one observational paper, researchers measured the urine and blood of 38 women from West Jakarta during their second trimester of pregnancy. The 20 women who were dehydrated were more likely to give birth to smaller babies, measured by both weight and length. The dehydrated women also—(surprise!)—tended to consume less water.

Other research has linked insufficient water intake to reduced amniotic fluid volume and milk supply. But that begs the question: what does sufficient fluid intake during pregnancy look like?

How Much Water Should You Drink While Pregnant?

You won’t find a consensus answer to this question. Different institutions have different guidelines, but I recommend ignoring them and adopting an intuitive approach.

Why shouldn’t we follow a guideline to drink X ounces of water per day? Because every woman’s body is different. For some women, X glasses won’t be enough. For others, X glasses will be too much. Both situations are risky.

For the average non-pregnant woman, the standard suggestion is to drink 8 ounces of water 8 times per day. This 8×8 meme sank into the culture decades before memes even existed, and—despite what science says to the contrary—simply won’t go away.

The problem is that drinking too much water dilutes blood sodium and leaves you fatigued, crampy, and nursing a headache. Notice how these symptoms mimic dehydration symptoms? People get confused and drink even more water! If things get really out of hand, this can even degenerate into confusion, dizziness, and even brain damage as you approach the low sodium state called hyponatremia.

Recommending we drink a set quantity of sodium-free fluids is dangerous and irresponsible. It’s bound to cause problems for a chunk of the population.

The better approach is to drink when thirsty. For most people—pregnant women included—thirst is perfectly designed to calibrate your fluid needs. Some explanation will help.

Let’s say you have a particularly sweaty workout. As you lose fluids through sweat, your blood volume decreases. Your brain takes note. Specialized receptors detect the falling blood volume and rush to a brain region called the hypothalamus. Then the hypothalamus makes you thirsty, you drink something, and fluid balance is restored.

Well, almost. Drinking to thirst is only half of it. You also need sodium.

The Importance of Sodium During Pregnancy

Sodium is the most under-appreciated pregnancy nutrient. Many women avoid salt because of the salt-causes-high-blood-pressure myth, and it makes me sad to see the consequences.

When a pregnant woman is sodium deficient, she’s more likely to give birth to an underweight baby. The baby is also more likely to have impaired kidney function, a malformed cardiovascular system, and growth issues.

Babies continue to need sodium after leaving the womb. In one paper, higher sodium intakes in premature babies were linked to higher IQs later in life.

As I mentioned earlier, sodium is a key component of breast milk. And speaking anecdotally, increasing sodium intake tends to increase milk supply in nursing moms.

I’ve heard from dozens of inspiring women who have used LMNT—not just for their own supply—but to donate milk to others. I wish I knew about sodium when I was pregnant and nursing, and I’m trying to help as many women as possible to get the salt they need. Please help me get the word out.

How to Hydrate During Pregnancy

During pregnancy, your body uses more water. Because of this, the risk of dehydration goes up.

But the solution isn’t to keep refilling your glass, regardless of thirst. That carries risks too, and these risks (the risks of low sodium) are arguably greater.

The solution is to drink when thirsty. When you drink to thirst, you replace only the fluids you need. You won’t overdo it.

While pregnant, you’ll likely need more fluids than you’re used to. And consuming those extra fluids might disrupt your normal routine. But hey, being pregnant is the best way to destroy most routines, am I right? Listen to your body and form a new one that works best for you.

You’ll also want to stay salty while pregnant or nursing. This means getting enough sodium from the salt shaker and drinking electrolyte water made with plenty of salt. We use LMNT in our house every day because it contains enough sodium to make a difference, along with science-backed ratios of potassium and magnesium.

In the end, proper hydration plays a big role in keeping you and your baby as healthy as possible. I hope this article helps you nail it!

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