Pregnancy changes how and when you sleep. This is thought to be due to a variety of factors such as hormone changes, discomfort, frequency of urination, restless legs syndrome, muscle cramps, mood changes, sleep apnea and chronic medical conditions.
There are two types of sleep, Rapid Eye Movement Sleep (REM) and Non- Rapid Eye Movement Sleep (NREM). NREM is divided into 3 stages: Stage 1 (S1) is a light drowsy state of sleep that is non refreshing. We normally spend less than 5-10% of our time in this stage of sleep. Stage 2 (S2) is the first true stage of sleep. Occasional large brain waves generated deep within the brain appear during S2. We are in S2 45- 50% of the night. Stage 3 (S3) is also known as deep sleep. It is characterized by large brain waves that come less frequently than during wakefulness and S1 or S2 sleep. We spend 25% of our sleep time in S3.
Here's how your sleep changes during pregnancy.
During first trimester Stage 1 of NREM sleep increases whereas stage 3 of NREM decreases and sleep efficiency decreases compared to the pre-pregnancy period. During the first trimester there is an increase in fatigue.
Total night-time sleep time decreases. Compared to the first trimester, there is an increase in deep sleep.
During the third trimester 98% of women complain of sleep disturbance. There is a decrease in the amount of REM sleep and deep sleep. The amount of stage 1 sleep, a light non-restorative stage of sleep is increased. Sleep complaints during the third trimester are most often related to discomfort caused by backache, urinary frequency, fetal movements, GERD and leg discomfort.