Why Does Pregnancy Make You Tired?

For anyone familiar with pregnancy, it's no surprise it goes hand in hand with fatigue. In fact, a 1998 study by the National Sleep Foundation reported that 78% of women experience more interrupted sleep during pregnancy1. And while fatigue is normal and to be expected, what causes it? Rather than just one contributing factor, there are several at play during pregnancy that drastically impact an expectant mother's need for sleep. Not only are there different causes for tiredness and exhaustion, but there are different time frames when they occur, as well.

Fatigue During the First Trimester

Whether you've experienced first-trimester fatigue before or not, the extent of just how tired you become during the first trimester can still feel overwhelming. But when you look at the changes happening in your body, it's no wonder why you feel so drained.

The following contribute directly to pregnancy fatigue in the first trimester:

  • Hormone changes. Your body will see increased production in estrogen, progesterone, prolactin, hCG, and hPL2. These, along with other hormones and adjusting adrenal and thyroid levels, will all take a toll on your energy levels as your body prepares itself for your baby.
  • Increased progesterone. Progesterone is needed for increased laxity in your joints and ligaments, as well as for your growing uterus. However, increased progesterone can also make you feel sleepier than normal.
  • Lower blood sugar levels. Lower blood sugar levels, or hypoglycemia, can occur if you aren’t eating enough. As your baby’s need for glucose grows, it’s important to keep your blood sugar levels stable and your calorie intake consistent. Hypoglycemia among pregnant women is most common in those with diabetes.
  • Lower blood pressure. Lower blood pressure, or hypotension, occurs as your circulatory system expands and hormonal changes contribute to the dilation of blood vessels. As a result, you can feel faint, dizzy, or lightheaded.
  • Lower iron levels. Much-needed iron is now also going to your baby which can leave you feeling run down.
  • Faster pulse and breathing rate. Pregnancy causes more blood to circulate through your body and, with it, comes a faster heart rate.

It's important to note that the fatigue you're feeling is also amplified when you combine these physical changes with some of the most common symptoms of the first trimester--such as morning sickness, headaches, and frequent urination. Trying to mitigate these symptoms is crucial; follow your doctor’s advice and try to get more rest when you can.

The first trimester is truly the foundation phase for both you and your baby. Your body is growing the placenta, the life-support system for your baby. The major organs of your baby are growing as well. So even though it may not even appear as though you are pregnant yet, all the building blocks are being put into place for the following two trimesters.

The Second Trimester: Hello Energy, My Old Friend

As the second trimester begins, you may notice your energy levels returning to normal. This is mainly because your body has almost finished growing the placenta. This process is no small (or easy) feat, and one that took an incredible amount of energy during the first trimester. So, while you may still feel exhausted, chances are it won’t feel as extreme as it did the first 12 weeks of your pregnancy. Another noticeable reason for feeling more energetic is simply because you have become more accustomed to the varying hormonal and emotional changes. Early pregnancy symptoms such as the nausea and vomiting of morning sickness usually subside by the second trimester, which can contribute to better sleep and calorie intake--resulting in more energy. Many women use this newfound energy for preparation and planning before the third trimester—when a different kind of fatigue begins.

Fatigue During the Third Trimester

By the third trimester, fatigue returns, albeit in a somewhat different form. In fact, approximately 60% of pregnant women report feeling fatigued during the third trimester3. Your tiredness is now caused less by extreme hormonal changes and more by the physical adjustments to the growing baby inside you. The most notable changes are:

  • Baby weight. You’re now feeling the effects of carrying an extra 20-30 pounds of baby weight with you—everywhere. Many women experience the added back and leg strain that comes along with it, adding a whole new kind of tired into the mix.
  • A growing uterus. Room for your other vital organs is now hard to come by, as your uterus grows and needs more room. You may feel deeper aches and pains as a result.
  • Frequent urination. No stranger to any expectant woman at this point, frequent urination will continue to interrupt your sleep. Between a crowded bladder and the need to stay hydrated, this third trimester symptom is an unfortunate bedfellow.

You might feel as though you’ve been running a marathon—or even an Ironman—by now and the truth is, you are. The hormonal, physical, and emotional changes your body endures to sustain not one—but two lives—continue to be a testament to the strength of women everywhere. Fatigue during pregnancy is not only normal and expected, it’s physical proof that you’re doing something extraordinary.