Sleep in late pregnancy: what's happening, what helps

This article is for general information, not medical advice. It has not been reviewed by a clinician, and no app tool replaces clinical care. If you have concerns about your sleep, your health, or your baby during pregnancy, contact your midwife or GP. For anything urgent, contact your maternity unit or local emergency number at any hour.

Why does sleep get so hard in the third trimester?

Sleep in late pregnancy breaks down for several reasons at once, not just one. The physical causes include the growing uterus pressing on the bladder (nocturia becomes near-universal in the third trimester), gastro-oesophageal reflux that intensifies when you lie flat, leg cramps and restless legs, fetal movement waking you in the night, and the mechanical difficulty of finding a comfortable position. Hormonal changes amplify all of it: elevated progesterone raises respiratory secretions and contributes to snoring; the disruption to circadian rhythm that accumulates through pregnancy affects how easily you fall back to sleep once woken. (Insomnia and sleep deficiency in pregnancy, Sleep Medicine Reviews, 2016, PMC4935047)

This is not a single problem with a single fix. A person dealing with heartburn at 2am needs a different adjustment than someone whose legs will not keep still, and both are different from someone who wakes for the toilet three times a night and cannot get back to sleep. Identifying which mechanisms are driving your disruption is the first useful step.

The most commonly reported complaint in research is night waking: by late pregnancy, almost all pregnant women wake at least once in the night, and waking time increases as gestation progresses. (Common sleep disorders in pregnancy: a review, BMC Pregnancy and Childbirth, 2023, PMC10475609)

Last reviewed: 19 July 2026.

How much sleep are you actually losing?

The third trimester has the worst sleep of pregnancy, and the numbers are worse than most people expect. A 2021 meta-analysis of 28 studies found the pooled prevalence of insomnia in the third trimester was 42.4 percent, meaning nearly half of all pregnant women in late pregnancy meet the diagnostic threshold for insomnia disorder. (Quach et al., A systematic review and meta-analysis of prevalence of insomnia in the third trimester of pregnancy, BMC Pregnancy and Childbirth, 2021, PMC8034118) Sleep duration shortens measurably as pregnancy progresses, averaging 6.6 to 7.8 hours per night by late pregnancy, compared to pre-pregnancy baselines. The most common cause of the shortfall is extended time awake after waking in the night, not difficulty falling asleep initially.

Two things are worth naming plainly. First, this is common enough that it is not a sign of fragility or failure. Second, common does not mean harmless. Observational evidence has linked short sleep in late pregnancy with higher rates of gestational diabetes and preeclampsia, and with longer labour. (Facco et al., Sleep disruption and adverse pregnancy outcomes, American Journal of Obstetrics and Gynecology, 2010, PMC3428677) The causal direction is uncertain in most of this literature: poorer health probably disrupts sleep as much as disrupted sleep harms health outcomes. But the association is real enough to take sleep seriously as something worth actively trying to improve.

Going to sleep on your side: what the evidence says

From 28 weeks, the evidence supports going to sleep on your side rather than on your back. A 2019 individual participant data meta-analysis of five case-control studies, published in eClinicalMedicine by The Lancet, found that going to sleep in the supine position was associated with an adjusted odds ratio of 2.63 for late stillbirth (95% CI 1.72 to 4.04) compared with going to sleep on the side. The population attributable risk was estimated at 5.8 percent. (Gordon et al., An individual participant data meta-analysis of maternal going-to-sleep position, interactions with fetal vulnerability, and the risk of late stillbirth, eClinicalMedicine, 2019) The Perinatal Society of Australia and New Zealand (PSANZ), whose guidance agrees with RANZCOG’s on this issue, issued a formal position statement advising pregnant women to sleep on their side and avoid the supine going-to-sleep position in late pregnancy. (PSANZ Position Statement: Mothers’ going-to-sleep position in late pregnancy)

The proposed mechanism is compression of the inferior vena cava by the gravid uterus in the supine position. This reduces maternal cardiac output and uterine blood flow. ACOG notes that lying on your back in the second and third trimesters may compress a major blood vessel, make you feel dizzy, and may reduce blood flow to your uterus. (ACOG, Can I sleep on my back when pregnant?)

Three things the evidence does not support are worth naming clearly. First, there is no difference between left and right side: both carry equivalent risk, and you should sleep on whichever is more comfortable. Second, the risk applies to your going-to-sleep position. If you wake in the night and find you have rolled onto your back, you do not need to panic. Roll onto your side and go back to sleep. You cannot control your position while asleep. Third, this one behavioural change is modest in population-level effect. It is worth making, but it is not a guarantee of any outcome.

A firm pregnancy pillow supporting the knees and belly makes the side position significantly more comfortable for most people, and reduces the tendency to roll. (NHS, Tiredness and sleep problems in pregnancy)

Restless legs at night: why it happens and what can help

Restless legs syndrome (RLS) affects between 10 and 34 percent of pregnant women, at roughly two to three times the rate seen outside pregnancy, making it the most common sleep-related movement disorder in pregnancy. (Silva et al., Prevalence and factors associated with restless legs syndrome among pregnant women in middle-income countries: a systematic review and meta-analysis, Sleep Medicine Reviews, 2024, PMC10771314) The core symptom is an urge to move the legs, usually at rest and in the evening or night, that is at least partially relieved by movement. For many people it is most intense in the second half of the night, just when sleep should be deepest. It typically gets worse through the third trimester and resolves for most people shortly after birth.

The leading proposed mechanisms are changes in iron and folate status and the rise in oestrogen during pregnancy. Iron is required for dopaminergic function in the brain, and RLS is closely associated with iron deficiency even outside pregnancy. Low haemoglobin is one of the identifiable risk factors for RLS in pregnancy. If your iron stores are borderline going in, pregnancy’s additional demands can tip the balance. (Ağargün et al., Restless legs syndrome and pregnancy: prevalence, possible pathophysiological mechanisms and treatment, Sleep Medicine, 2015, PMC5562408)

What can help: mention significant RLS symptoms to your midwife or GP. A blood test to check iron and ferritin levels is a logical first step, and iron supplementation can reduce symptoms when deficiency is identified. Stretching before bed and heat applied to the legs ease symptoms for some people. Avoiding caffeine and antihistamines (which worsen RLS) is worth trying. Pharmaceutical treatments such as dopamine agonists are generally not recommended in pregnancy except under specialist supervision for severe cases.

What actually helps with pregnancy sleep?

The intervention with the strongest randomised trial evidence for insomnia in pregnancy is cognitive behavioural therapy for insomnia (CBT-I). Multiple RCTs have tested CBT-I in pregnant women, delivered both in-person and as digital programs. A 2019 RCT published in Sleep found significant reductions in insomnia symptoms in pregnant women receiving CBT-I, with effects that extended into the postpartum period. (Felder et al., Cognitive Behavioral Therapy for Prenatal Insomnia: A Randomized Controlled Trial, Sleep, 2020, PMC6485299) A 2022 RCT of digital CBT-I in pregnancy found insomnia remission rates significantly higher at six months postpartum in the intervention group. (Manber et al., Randomized controlled trial of digital cognitive behavior therapy for prenatal insomnia symptoms: effects on postpartum insomnia and mental health, Sleep, 2022, PMC8842335)

CBT-I covers sleep restriction, stimulus control, cognitive restructuring, and sleep hygiene in a structured program of six to eight sessions. It is available in digital form, which most pregnant women in trial populations found acceptable. It also reduces anxiety and depressive symptoms as a secondary effect. Ask your GP or midwife about a referral or a validated digital program.

Melatonin does not have adequate evidence. A 2022 scoping review of all human studies on melatonin in pregnancy and lactation found the evidence base for both safety and efficacy too limited to support routine use for insomnia. Melatonin crosses the placenta and interacts with pregnancy hormones. Because no adequately powered safety RCT in pregnant women exists, most clinical bodies advise against it unless specifically prescribed. (Emet et al., Melatonin use during pregnancy and lactation: a scoping review of human studies, BMC Pregnancy and Childbirth, 2022, PMC9169489) If you are considering any supplement for sleep, check with your midwife or GP first.

Practical adjustments with modest or plausible benefit: keep the bedroom cool; avoid caffeine after midday; use a pregnancy pillow to maintain the side-sleeping position; avoid large meals close to bedtime to reduce reflux; if nocturia is the main disruption, bring your fluid intake forward to earlier in the day while keeping total daily intake up. None of these is a trial-supported treatment. Each can shift the disruption by one or two waking episodes per night, and that matters at the margin when you are already running short.

When poor sleep is worth mentioning to your midwife

Raise sleep problems at your next appointment if any of the following apply: you are consistently getting fewer than five or six hours, you have gone more than a week with significant disruption, you notice your mood declining alongside the sleep loss, or you have symptoms suggestive of restless legs. Short sleep in pregnancy is associated with higher rates of gestational diabetes and preeclampsia in observational data. (Reutrakul et al., Objectively measured short sleep duration and later sleep midpoint in pregnancy are associated with a higher risk of gestational diabetes, Diabetes Care, 2017) Your midwife or GP can check for treatable causes, discuss CBT-I referral, and decide whether any adjustments to your care are appropriate.

A brief note on sleep apnoea: snoring increases in pregnancy due to progesterone-driven mucosal swelling, and obstructive sleep apnoea is more prevalent in pregnancy than often recognised. If you or your partner notice gasping, choking, or significant pauses in your breathing while asleep, mention it to your provider. It is a separate, diagnosable, and treatable condition.

What myCocoon does with your sleep data

myCocoon reads sleep duration and sleep stages from the Apple Health app with your permission. Those values go into a part of the app that is set up to never sync to iCloud or CloudKit. Apple’s HealthKit guidelines prohibit storing health data in iCloud, and the app follows that rule. The sleep data does not leave your phone in this form.

The app computes a sleep quality label (poor, fair, good, great) from your sleep hours each day. If your sleep hours were under five the previous night, the home screen may surface a brief card: “You got X hours of sleep last night. Try winding down earlier tonight.” This is a single-signal check against your own reading. It is not a clinical assessment, it does not compare you against population norms, and it carries no medical weight. It is a quiet note, not an alert.

If you have Cloud AI turned on in Settings, your most recent sleep hours are included in the structured summary sent to Google’s Gemini when you ask the app a question. When Cloud AI is off, which is the default, sleep data stays on your phone entirely. You can check and change your Cloud AI setting at any time in Settings.

myCocoon is live on the App Store now, on iPhone with iOS 26 or later. It is newer and smaller than apps like Flo or What to Expect, with no Android version and no community feed. What it does instead is keep your health data private, run no ads, and charge a flat subscription with no upsells.

Common questions

Is it normal to sleep badly in the third trimester? Yes. A 2021 meta-analysis found insomnia prevalence of 42 percent in the third trimester, and sleep duration shortens measurably as pregnancy progresses, averaging 6.6 to 7.8 hours by late pregnancy. Frequent night waking is the most common complaint. Most physical causes resolve after birth.

Is it dangerous to sleep on my back while pregnant? The evidence supports avoiding going to sleep on your back from 28 weeks. An IPD meta-analysis of five case-control studies found supine going-to-sleep position was associated with 2.6 times the late stillbirth risk compared with side-sleeping. The risk is specifically about your going-to-sleep position. If you wake up on your back in the night, roll onto your side and go back to sleep. You cannot control your position while asleep, and this is not something to panic about.

Does it matter whether I sleep on my left or right side? No meaningful difference. RCOG and the Perinatal Society of Australia and New Zealand both note that left and right side-sleeping carry equivalent risk. The evidence showing increased stillbirth risk is specific to the supine position. Sleep on whichever side is more comfortable.

Can I take melatonin to sleep while pregnant? Most clinical bodies advise against it. Melatonin crosses the placenta, and a 2022 scoping review found the evidence base for both safety and efficacy in pregnancy too limited to support routine use. CBT-I has the strongest trial evidence in pregnant women and carries no pharmacological risk. Talk to your midwife or GP before taking any supplement.

What actually helps insomnia in pregnancy? CBT-I has the best trial evidence: multiple RCTs show it reduces insomnia symptoms during pregnancy and into the postpartum period. A pregnancy pillow to support side-sleeping, treating restless legs if identified, and reducing caffeine and large evening meals are reasonable adjustments. Most pharmaceutical sleep aids are not recommended in pregnancy, and melatonin has inadequate safety evidence.

Can poor sleep during pregnancy harm my baby? Observational studies link short sleep duration with higher rates of gestational diabetes, preeclampsia, and longer labour. The association is real, but the causal direction is uncertain in most of this literature. Take sleep seriously enough to raise it with your midwife. Do not treat it as an extra cause for alarm on its own.

Bottom line

Sleep in the third trimester is hard for almost everyone, and the numbers back that up: roughly half of women meet the clinical threshold for insomnia by 28 weeks. Most of the causes are physical and will resolve after birth. A few are worth acting on now. Go to sleep on your side from 28 weeks. If restless legs are disrupting your night, ask about iron levels at your next appointment. If the disruption is consistent and affecting your mood, ask for a CBT-I referral. Skip melatonin. Raise it with your midwife if you are consistently getting under six hours, especially if you have risk factors for gestational diabetes or preeclampsia. And if you wake up on your back in the night, roll over and go back to sleep without worrying about it.

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