Sleep patterns change throughout pregnancy, largely
as a result of the enormous physical changes that take place as the
fetus grows, but also partly due to hormonal changes that occur.
Sleep during the first trimester
The first trimester is the
period from conception to 3 months. During this time, the high levels of
progesterone in the body have a sleep-inducing and sedating effect on
the brain. Progesterone also increases the need to urinate due to the
effect it has on the smooth muscle in the bladder. Women often
experience more sleep difficulty during the night due to an increased
need to go to the bathroom. Many women experience daytime sleepiness and
fatigue during this time. Nausea and vomiting is not just limited to
“morning sickness” but can also occur in the evening. There is a greater
tendency to sleep longer than prior to pregnancy, but there is less
slow wave sleep during this time.
Sleep during the second trimester
The second trimester
of pregnancy is the period from the fourth to the sixth month.
Progesterone levels continue to rise during this period but more slowly.
Many women experience a great improvement in their sleep quality and
quantity during this period and report more daytime energy. The growing
fetus moves above the bladder and the need to urinate decreases.
However, many women start to snore at this stage, probably because of
the effects of estrogen on blood vessels, resulting in nasal congestion.
During this time, there is an increased risk of developing sleep apnea
and also high blood pressure, so you must be carefully monitored by your
doctor. There is less slow wave sleep than prior to pregnancy and more
time is spent awake during the night.
Sleep during the third trimester
The third trimester is
the period from the seventh to the ninth month. Progesterone levels are
at their peak during this time. Women report the most sleep difficulties
during this stage of pregnancy. Sleep disturbances are very common and
are caused by a wide variety of factors, including leg cramps,
heartburn, nasal congestion, and an increased need to urinate. The
baby’s movements can also disturb sleep. In the last few weeks of
pregnancy, many women find achieving a comfortable sleeping position
difficult. This can lead to increased daytime fatigue and sleepiness.
Breast tenderness, shortness of breath, and irregular uterine
contractions can also affect sleep adversely. Overall, more time is
spent awake and there is less slow wave sleep.
