Fatigue in pregnancy is an overwhelming, persistent exhaustion that goes well beyond normal tiredness. It affects the vast majority of pregnant women: in a study of 605 pregnant women, 94.2% reported experiencing fatigue during their pregnancy, with rates above 90% in every trimester. This isn’t a sign that something is wrong. Your body is doing an extraordinary amount of work to grow a new human, and that work has a real energy cost.
Why Pregnancy Is So Physically Demanding
The fatigue you feel has a straightforward explanation: your cardiovascular system is working dramatically harder than it did before pregnancy. Total blood volume increases by roughly 45% above pre-pregnancy levels (and can climb even higher), while red blood cell production ramps up by as much as 40%. Your heart responds by increasing its output by up to 45% by week 24, first by pumping more blood per beat and later by beating faster.
All of this exists to meet the increased metabolic demands of both your body and the growing fetus, ensuring enough blood reaches the placenta for fetal development. Even at rest, your oxygen consumption is significantly higher than it was before pregnancy. Your body is essentially running a low-grade endurance workout around the clock, which is why sitting on the couch can feel like you just climbed a flight of stairs.
When Fatigue Peaks and Eases
Fatigue typically hits hardest in the first trimester, peaking around weeks six to eight. This is when hormonal shifts are most dramatic and your body is adjusting to the new demands of early pregnancy. For many women, this phase feels almost flu-like: a bone-deep tiredness that sleep doesn’t fully fix.
The second trimester often brings a noticeable burst of energy. Your body has adapted to the hormonal changes, the placenta is fully functioning, and many women describe this stretch as the most comfortable part of pregnancy. It’s not a return to your pre-pregnancy energy level, but the contrast with the first trimester can feel significant.
Then fatigue returns in the third trimester, this time driven by different factors. The physical weight of the baby strains your back, hips, and legs. Sleep becomes harder to come by as frequent urination, leg cramps, and difficulty finding a comfortable position disrupt your nights. In one study of late-pregnancy sleep quality, 83.9% of women with poor sleep reported leg pain or cramps, and 88.2% reported back, waist, or neck pain. Poor sleep and fatigue feed each other in a cycle that’s difficult to break in those final weeks.
What Makes It Worse
Several factors can amplify pregnancy fatigue beyond what’s typical. Stress is a significant one: women with higher perceived stress levels consistently report worse sleep quality and greater fatigue. Restless leg syndrome, a condition where your legs feel an uncomfortable urge to move, becomes more common during pregnancy and can make falling asleep or staying asleep much harder.
Nausea and vomiting, especially in the first trimester, drain energy directly. If you’re struggling to keep food down, your body has fewer calories to work with on top of its already elevated demands. Carrying multiples amplifies every cardiovascular change, since blood volume and cardiac output need to increase even further.
Normal Fatigue vs. a Medical Problem
While fatigue is nearly universal in pregnancy, sometimes it signals an underlying condition that needs treatment. The two most common culprits are iron deficiency anemia and thyroid dysfunction.
Iron Deficiency Anemia
Your body needs significantly more iron during pregnancy to support the increase in blood volume and red blood cell production. When iron stores run low, your blood can’t carry oxygen as efficiently, leaving you feeling exhausted, dizzy, or short of breath. Anemia in pregnancy is typically identified when hemoglobin drops below 11 g/dL in the first or third trimester, or below 10.5 g/dL in the second trimester. Iron deficiency can exist even without full-blown anemia: ferritin (the protein that stores iron) below 30 ng/L during any trimester suggests your iron reserves are depleted. If your fatigue feels disproportionate, or comes with pale skin, rapid heartbeat, or breathlessness, a simple blood test can check for this.
Thyroid Problems
Hypothyroidism, where your thyroid gland doesn’t produce enough hormone, shares many symptoms with normal pregnancy: fatigue, weight gain, constipation, feeling cold, and trouble concentrating. That overlap makes it easy to miss. The diagnostic threshold is lower during pregnancy than at other times. TSH levels above 2.5 mU/L in the first trimester or above 3.0 mU/L in the second and third trimesters may indicate a problem, compared to the standard cutoff of 4.0 mU/L outside of pregnancy. Subclinical hypothyroidism, where TSH is elevated but thyroid hormone levels are still normal, is the most common thyroid issue in pregnancy and is treatable.
What Actually Helps
Exercise is one of the most effective tools for managing pregnancy fatigue, even though it might be the last thing you feel like doing. The American College of Obstetricians and Gynecologists recommends 150 minutes of moderate-intensity aerobic activity per week during a healthy pregnancy. That translates to about 30 minutes on five days, or shorter 10-minute sessions spread throughout the day. Moderate intensity means you’re moving enough to raise your heart rate and sweat, but you can still hold a conversation. Brisk walking, gardening, and swimming all qualify.
If you weren’t active before pregnancy, start with just five minutes a day and add five minutes each week. Even small amounts of movement improve circulation, mood, and energy levels. The goal isn’t to push through exhaustion but to build a baseline of activity that helps your body manage its increased workload more efficiently.
Sleep hygiene matters more during pregnancy than at almost any other time. Going to bed and waking at consistent times, keeping your room cool and dark, and using pillows to support your belly and hips in the third trimester can all improve sleep quality. Napping during the day, when possible, is not laziness during pregnancy. It’s a legitimate response to a body that’s consuming more energy than usual every hour of every day.
Nutrition plays a direct role too. Eating smaller, more frequent meals helps maintain steady blood sugar and prevents the energy crashes that come from long gaps between eating. Iron-rich foods like lean red meat, beans, spinach, and fortified cereals support the massive increase in red blood cell production. Pairing these with foods high in vitamin C improves iron absorption.
Staying hydrated is easy to overlook, especially if nausea makes drinking water unappealing, but dehydration worsens fatigue and can contribute to headaches and dizziness. Keeping water accessible throughout the day and sipping consistently, rather than trying to drink large amounts at once, tends to work better when nausea is a factor.