Not drinking enough water during pregnancy can lead to a range of problems, from persistent constipation and headaches to more serious complications like low amniotic fluid around your baby. Your body’s demand for water increases significantly once you’re pregnant, and falling short of that demand affects both you and your baby in measurable ways.
Why Your Body Needs More Water During Pregnancy
Your blood volume starts rising as early as six to eight weeks of pregnancy and peaks around weeks 32 to 34, increasing by 30 to 45 percent. In practical terms, that means your body produces an extra 1,200 to 1,800 milliliters of blood compared to before pregnancy. Water makes up roughly 83 percent of blood, so this expansion alone creates a substantial new demand for fluids.
On top of that, your kidneys are working harder, your metabolism is running faster, and your body is building an entirely new organ (the placenta) while maintaining the amniotic fluid that cushions your baby. Water is also essential for digesting and absorbing the extra nutrients pregnancy requires. All of this means your baseline fluid needs jump considerably. The American College of Obstetricians and Gynecologists recommends 8 to 12 cups (64 to 96 ounces) of water daily during pregnancy. The Institute of Medicine sets the total water intake target at about 3,000 milliliters per day, which includes water from food.
Low Amniotic Fluid
One of the more serious consequences of chronic under-hydration is reduced amniotic fluid, a condition called oligohydramnios. Amniotic fluid protects your baby from compression, allows room for movement and lung development, and helps maintain a stable temperature. When fluid levels drop too low, the risks include umbilical cord compression, breech positioning, concentrated meconium in the fluid, and, in severe early cases, impaired lung development.
The good news is that maternal hydration has a direct, measurable effect on amniotic fluid volume. A Cochrane systematic review found that simple oral hydration increased the amniotic fluid index in women with oligohydramnios by an average of about 2 centimeters, and in women with normal fluid levels by about 4.5 centimeters. That’s a meaningful clinical difference, and it suggests that staying hydrated is one of the simplest things you can do to maintain healthy fluid levels around your baby.
Constipation and Digestive Problems
Pregnancy already slows your digestive system. Hormonal changes relax the smooth muscle in your intestines, which means food moves through more sluggishly. When you add dehydration on top of that, constipation becomes significantly worse. Your body pulls water from your colon to meet its other needs, leaving stool harder and more difficult to pass.
Increasing fluid intake is considered the first line of relief for pregnancy constipation, alongside dietary fiber and moderate exercise. While these measures don’t resolve every case, many pregnant people find that simply drinking more water throughout the day makes a noticeable difference in regularity and comfort.
Urinary Tract Infections
Pregnancy already raises your risk of urinary tract infections because of changes in how your urinary system functions. When you’re not drinking enough water, your urine becomes more concentrated, creating a more favorable environment for bacteria to multiply. Staying well-hydrated helps flush bacteria from the urinary tract before an infection can take hold. UTIs during pregnancy are not just uncomfortable. Left untreated, they can progress to kidney infections, which are linked to preterm labor.
Headaches, Fatigue, and Overheating
Dehydration is one of the most common triggers for headaches during pregnancy. When your fluid levels drop, blood volume decreases slightly and blood vessels can constrict, reducing oxygen flow to the brain. The result is a dull, persistent headache that often responds to a glass or two of water faster than it responds to rest alone.
Fatigue from dehydration compounds the tiredness you’re already feeling, especially in the first and third trimesters. Your heart has to work harder to pump a reduced volume of blood, which leaves you feeling drained even after adequate sleep. In warmer months or during exercise, dehydration also impairs your body’s ability to regulate temperature, which matters more during pregnancy because overheating can be harmful to fetal development.
Braxton Hicks Contractions and Preterm Concerns
Dehydration is a well-known trigger for Braxton Hicks contractions, the “practice” contractions that tighten your uterus without progressing into labor. While these are generally harmless, frequent or intense Braxton Hicks caused by dehydration can be alarming, and in some cases, persistent dehydration may contribute to irritability of the uterus that raises concern for preterm contractions. Many labor and delivery units will start by giving you fluids when you come in with contractions before 37 weeks, because rehydration alone often calms them down.
How to Tell You’re Not Drinking Enough
Your urine color is the most reliable daily indicator. Well-hydrated urine is pale yellow or straw-colored. As you drink less, it deepens to a darker yellow, and dehydration can push it toward amber or even orange. If your urine consistently looks darker than light lemonade, you’re likely not getting enough fluid.
Other signs to watch for include dry mouth, feeling lightheaded when you stand up, infrequent urination, and a general sense of fatigue that doesn’t improve with rest. During pregnancy, some of these symptoms overlap with normal pregnancy experiences, so urine color tends to be the most straightforward check.
When Dehydration Becomes a Medical Emergency
Severe morning sickness, known as hyperemesis gravidarum, is the most common reason pregnant people become dangerously dehydrated. It’s characterized by persistent vomiting, weight loss of more than 5 percent of pre-pregnancy body weight, dry mouth, and inability to keep food or fluids down. When vomiting is this severe, your body starts breaking down fat for energy, producing ketones that signal starvation-level metabolism.
If you can’t keep any fluids down for 12 to 24 hours, feel dizzy or faint, have a racing heartbeat, or notice you’re barely urinating, you need medical attention. Treatment typically involves intravenous fluids to rehydrate quickly and correct any electrolyte imbalances. Most people feel dramatically better within hours of receiving IV fluids, though some cases require ongoing management throughout pregnancy.
Practical Ways to Stay Hydrated
Hitting 8 to 12 cups a day sounds straightforward, but nausea, a shrinking stomach capacity in the third trimester, and simple forgetfulness make it harder than it seems. Sipping small amounts throughout the day is generally easier than trying to drink large volumes at once, especially if nausea is an issue. Keeping a water bottle visible wherever you spend time serves as a passive reminder.
Water doesn’t have to be your only source. Herbal teas (caffeine-free), milk, soups, and water-rich fruits like watermelon, oranges, and cucumbers all contribute to your daily total. If plain water is unappealing, adding slices of lemon, cucumber, or berries can make it more palatable. Sparkling water counts too. The key is consistent intake spread across the day rather than playing catch-up in the evening, which tends to lead to frequent nighttime bathroom trips without meaningfully improving hydration.