Pregnancy significantly disrupts sleep, and the effects start earlier than most people expect. Over 42% of pregnant women experience insomnia symptoms in the first trimester, and that number climbs to nearly 47% by mid-pregnancy. The causes shift as pregnancy progresses, ranging from hormonal changes that alter your brain’s sleep cycles to physical discomforts that wake you repeatedly through the night.
Why Pregnancy Hormones Disrupt Sleep
The core problem is a hormonal paradox. Progesterone and human chorionic gonadotropin, two hormones essential for maintaining pregnancy, are also powerful sedatives. They promote daytime sleepiness and earlier sleep onset, which sounds like it would help. But progesterone simultaneously fragments nighttime sleep, meaning you fall asleep easily yet wake up repeatedly. The result is a frustrating combination: you feel exhausted during the day but can’t stay asleep at night.
Progesterone also raises your core body temperature slightly, which works against the natural cooling your body needs to stay in deep sleep. Rising cortisol and growth hormone levels add another layer of disruption, further altering the time you spend in different sleep stages. These hormonal shifts begin in the first weeks of pregnancy, which is why extreme fatigue is one of the earliest signs many women notice.
How Sleep Changes Across Trimesters
In the first trimester, the dominant experience is overwhelming daytime sleepiness paired with lighter, more broken nighttime sleep. You may need to nap or go to bed hours earlier than usual. Nausea can also interrupt sleep, particularly if it strikes in the evening or early morning.
The second trimester brings modest relief for some women as hormone levels stabilize, though insomnia symptoms still affect close to half of all pregnant women during this period. Nighttime bathroom trips become more frequent as blood volume increases and the kidneys filter more fluid.
The third trimester is typically the hardest stretch for sleep. The physical bulk of a growing uterus makes it difficult to find a comfortable position. Heartburn worsens when lying down. Fetal movement peaks at night. And the need to urinate can wake you three or more times before morning. Many women report sleeping in fragments of just a few hours at a time by the final weeks.
Restless Legs and Other Sleep Disorders
Pregnancy can trigger restless legs syndrome, that creeping, crawling sensation in your legs that creates an irresistible urge to move them, particularly when you’re lying still at night. Having restless legs in a prior pregnancy is the strongest predictor, increasing the odds dramatically. Low iron stores play a role too, though they aren’t the only cause. If your ferritin level (a measure of stored iron) is below a certain threshold, iron supplementation can help reduce symptoms. This is worth mentioning to your provider if the sensation is keeping you awake.
Sleep apnea is the other condition that can emerge or worsen during pregnancy. Swelling in the upper airway, combined with hormonal changes that affect breathing muscles, narrows the space air has to travel through. Women with a higher BMI, chronic high blood pressure, or those carrying multiples face the greatest risk. The hallmark sign is loud, frequent snoring, especially if it’s new or getting worse as pregnancy progresses. Untreated sleep apnea during pregnancy is linked to complications like gestational diabetes and preeclampsia, so new or worsening snoring is worth bringing up at a prenatal visit.
Sleep Position in Late Pregnancy
Once you reach the third trimester, your sleep position matters. Lying flat on your back allows the weight of the uterus to compress the large blood vessel that returns blood from your lower body to your heart. This reduces blood flow to the placenta. A large meta-analysis published in JAMA Network Open found that women who regularly fell asleep on their backs after 28 weeks gave birth to babies weighing an average of 144 grams less than women who fell asleep in other positions. Back sleeping in late pregnancy is also associated with an increased risk of late stillbirth.
Sleeping on your side, particularly your left side, keeps this blood vessel uncompressed and maintains the best circulation to the uterus. If you wake up on your back, simply roll to your side. A pillow between your knees or behind your back can help you stay in position. You don’t need to worry about brief, unconscious position changes during the night. What matters most is the position you fall asleep in.
What Actually Helps
Non-medication strategies are the first line of defense. Keeping a consistent sleep schedule, even on weekends, helps reinforce your body’s internal clock. Limiting fluids in the two hours before bed can reduce overnight bathroom trips without affecting your overall hydration. Elevating the head of your bed or using a wedge pillow reduces heartburn. A cool bedroom, ideally around 65 to 68 degrees Fahrenheit, counteracts the temperature-raising effects of progesterone.
Magnesium supplements are commonly recommended for pregnancy-related leg cramps, but the evidence is mixed. A Cochrane review of eight trials found that magnesium may reduce how often leg cramps occur in some women, but results were inconsistent across studies. Some trials showed clear benefit while others showed no difference compared to placebo. Side effects like nausea and diarrhea were rare. If leg cramps are disrupting your sleep, magnesium is a reasonable option to discuss with your provider, but it’s not a guaranteed fix.
For general pregnancy insomnia, cognitive behavioral techniques like stimulus control (only using the bed for sleep, getting up if you can’t fall asleep within 20 minutes) and relaxation exercises have the best evidence without any safety concerns. Melatonin supplements lack sufficient safety data in pregnancy, and most clinical guidelines do not endorse their use during this period.
Sleep After Delivery
Sleep disruption doesn’t end at birth. In the first six months postpartum, infant feeding schedules fragment maternal sleep into short blocks. Research tracking mothers through the first year found that over half were still getting fewer than seven hours per night at both six and twelve months after delivery, with no significant improvement between those two time points. That’s a full year of insufficient sleep for the majority of new mothers.
This sustained sleep loss goes beyond simple tiredness. It’s associated with increased fatigue, mood disturbances, and daytime sleepiness that can affect everything from driving safety to emotional regulation. The sleep deprivation of late pregnancy, in other words, flows directly into the sleep deprivation of early parenthood. Planning for help with nighttime feedings, even a few nights per week, can make a meaningful difference in total sleep hours during those first months.