Pregnancy can have a significant impact on how a woman sleeps. In most cases, sleep disturbances are limited to insomnia (inadequate amount or quality of sleep). However, some pregnant women may also develop other sleep disorders such as sleep apnea or restless leg syndrome (sensations felt in the legs when at rest).

A recent poll by the National Sleep Foundation found that the majority of pregnant respondents reported some level of sleep disturbance. Women who are pregnant often report unusual levels of fatigue, especially during the first and third trimesters, due to these sleep disturbances.

Changing hormone levels are among the top causes of sleeping disorders in pregnant women. In addition, many women lose sleep as a result of anxiety about impending parenthood, the health of the fetus or a changing relationship with their partner.

Sleep concerns often initially appear during the first trimester. As progesterone levels rise in a pregnant woman’s body, drowsiness during daytime hours may occur. While total sleep time often increases in the first trimester, the quality of sleep declines. Body changes make it more difficult for many women to become comfortable while sleeping. This may cause delayed sleep and frequent awakenings during the night.

In addition, pregnant women experience a need to urinate more frequently that leads to waking at night to use the bathroom (nocturia). Rising progesterone levels inhibit the action of the body’s smooth muscles, which contract without a person’s conscious control. Inhibition of the smooth muscles is the main source of an increased need to urinate during the first trimester. Expansion of the uterus also shrinks the storage capacity of the bladder. Finally, the kidneys are increasingly taxed by the need to filter increased blood volume that occurs during pregnancy. All of these factors contribute to a more frequent need to urinate, increased awakenings and rougher sleep.

Because women are less rested during the first trimester of pregnancy, they may become fatigued, irritable and depressed. In addition, many women experience persistent bouts of nausea and vomiting during the first trimester. This condition is traditionally known as morning sickness (hyperemesis). Despite the name, nausea and vomiting can occur at any time of day during the first trimester and may also disrupt sleep.

In many cases, women who experience sleep disruption during the first trimester often have less trouble during the second trimester. Nausea may begin to dissipate during the second trimester of pregnancy, hormonal changes start to stabilize and women often find less need to use the bathroom as the uterus moves higher into the abdomen. The second trimester is often a time when women begin to sleep more normally.

However, during the second trimester, many women report an increased frequency of nightmares, which may disrupt sleep. Heartburn may also disrupt sleep at this time, often caused by the expanding uterus and the slowed movements of gastrointestinal muscles (due to increased progesterone levels).  

During the third trimester, women generally experience a return to the sleep difficulties of the first trimester. In many cases, these sleep problems are intensified during the third trimester. As a woman’s body increases in size, she is likely to grow increasingly tired. She may find it even more difficult to become comfortable during sleep and will once again experience an increased need to urinate.

The vast majority of pregnant women frequently awaken throughout the night during the third trimester. They also begin to snore and to experience back pain and other discomforts that may interfere with sleep. A recent poll by the National Sleep Foundation found that up to 15 percent of women develop restless leg syndrome during the third trimester. This condition is characterized by uncomfortable feelings in the legs that prevent sleep, and it is often caused by iron deficiency. For most women, the condition resolves after pregnancy.

Lack of proper sleep during late pregnancy can significantly impact a woman’s delivery. Studies show that women who receive inadequate sleep during the last month of pregnancy may be at increased risk of a longer period of labor or require delivery by Caesarean section (C-section). Women are encouraged to discuss their sleeping patterns with their physician during regular prenatal care visits.

Other factors that may negatively impact a pregnant woman’s ability to sleep include:

• Faster heart rate. A woman’s heart rate increases during pregnancy to pump the increased volume of blood.
  
  
• Shortness of breath. The expanding uterus can place increased pressure on the diaphragm (muscle between the chest and abdomen), which can make it more difficult to breathe. In addition, pregnant women must breathe faster and more deeply due to an increased need for oxygen.
  
  
• Aches and pains. The dramatic bodily changes that occur during pregnancy can lead to backaches, leg cramps and other pains that may hinder a pregnant woman’s ability to sleep. For example, hormonal changes cause the ligaments between bones and joints to loosen and cause pain that can disrupt sleep.
  
  
• Fetal movements. The movements of a fetus may be active enough to disrupt a woman’s sleep.