Sleep Changes in Pregnancy: A Trimester by Trimester Guide

Q: Why am I so tired in the first trimester but still not sleeping well at night?

This is really common in early pregnancy. Progesterone rises fast and has a sedative effect by day, so the tiredness can feel relentless. The same hormone can also cut down your deep sleep at night and wake you more often, including for trips to the bathroom. So you end up sleepy through the day even after a night in bed.

Q: Does sleep genuinely improve in the second trimester for everyone?

You may well find sleep feels more settled in the second trimester. Progesterone stops climbing as quickly, which tends to ease the daytime tiredness, and nausea has often calmed by now. Your nights might still be broken, even so. Towards the end of the trimester, a growing bump and the start of snoring can begin to affect how well you sleep.

Q: What causes restless legs in the third trimester and should I see my GP?

Restless Legs Syndrome (RLS) in pregnancy is linked to hormonal shifts and possibly to low iron, though the exact reason is not fully pinned down. You feel an urge to move your legs along with an uncomfortable sensation that is worse at rest and at night. If this sounds like you, it is worth raising with your midwife or GP. Since low iron can play a part, you need a proper check before changing anything about supplements.

Q: Why does heartburn get worse at night in late pregnancy?

Two things team up to make heartburn worse when you lie down. Pregnancy hormones relax the valve between your gullet and your stomach, so acid travels up more easily. Your growing womb also presses up on your stomach, adding to that pressure. Lying flat takes away the gravity that would otherwise help keep acid where it belongs. Your midwife or pharmacist can talk you through ways to ease it in pregnancy.

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The heaviness that sets in during early pregnancy, the kind that makes staying awake past mid-afternoon feel impossible, is often one of the first signs that your sleep is going to shift over the coming months. Sleep changes through pregnancy trimester by trimester, and what wakes you at week eight is rarely what wakes you at week thirty-four. Knowing what sits behind each change gives you a clearer picture of what your body is doing, and when it is worth raising something with your midwife.

First trimester sleep: progesterone and exhaustion

The drowsiness that pulls at you in the first trimester comes largely down to progesterone, a hormone that rises quickly in these early weeks. It has a calming, sedative effect, which is why daytime tiredness can feel so heavy. The odd part is that the same hormone that makes you drowsy by day can also pull you out of deep sleep at night and wake you more often.²

Progesterone also softens the smooth muscle throughout your body, including the muscles around your bladder. That often means more trips to the bathroom through the night, on top of sleep that is already lighter and less restful.³

This leaves you with a particular kind of tiredness, heavy and steady through the day, yet not really lifted by a full night in bed. It can be one of the more disorienting parts of early pregnancy.

Second trimester sleep: why rest often improves

Sleep often feels more settled in the second trimester. Progesterone stays high, but it stops climbing as fast, and that steadier level tends to take the edge off the daytime tiredness. By this stage nausea has often eased too, though yours may linger a little longer.⁴

This calmer stretch tends not to last the whole trimester. Towards the end of it, your growing bump can make a comfortable sleeping position harder to find. Your nasal passages may also swell, partly from pregnancy hormones and the extra blood your body is carrying, and that can bring on snoring.⁵

Third trimester sleep: reasons why rest becomes harder

By the third trimester, several physical changes can land on your sleep at once. Looking at each one on its own makes it easier to work out what you are feeling.

Physical discomfort and back pain

The size and weight of your baby and womb make a comfortable position harder to find. Back pain and sore muscles are common, and the ligaments around your pelvis soften around this time, which can add to the ache. If back or pelvic pain is strong or hangs around, it is worth mentioning to your midwife, who can point you towards support.⁶

Frequent night-time trips to the bathroom

As your baby grows and settles lower in your pelvis, there is more pressure on your bladder. That can have you waking to wee several times a night. It is a different cause from the early-pregnancy version, which came from progesterone softening muscle. This time it is mostly about physical pressure.⁷

Heartburn at night

Heartburn can be especially disruptive at night. Pregnancy hormones relax the valve that normally keeps stomach acid in place, and your growing womb presses up on your stomach, pushing acid into your gullet. Lying down makes it worse, which is why the burning often flares once you get into bed. If heartburn is breaking your sleep, your midwife or pharmacist can talk you through options that are safe in pregnancy.⁸

Restless Legs Syndrome in pregnancy

That overwhelming urge to move your legs, often with a crawling or creeping feeling, is Restless Legs Syndrome (RLS). It is common in pregnancy and turns up most in the third trimester. The feeling tends to be worse when you are resting and at night, which makes both falling asleep and staying asleep hard. The exact cause is not fully clear, though it may be tied to hormonal shifts or low iron.⁹

Sleep in pregnancy is rarely simple at any stage, and each of these changes comes back to something real your body is doing. From your third trimester onwards (after 28 weeks), it is also important to go to sleep on your side for both night sleep and daytime naps. Research shows that sleeping on your side is safer for your baby, as going to sleep on your back in late pregnancy increases the risk of stillbirth. While the overall risk of stillbirth remains low, side-sleeping is a simple habit that lowers it even further. If any of these changes are taking a serious toll on your sleep, or you are unsure whether what you are feeling is normal, your midwife is the right first person to ask.¹

Frequently Asked Questions

Why am I so tired in the first trimester but still not sleeping well at night?

Does sleep genuinely improve in the second trimester for everyone?

What causes restless legs in the third trimester and should I see my GP?

Why does heartburn get worse at night in late pregnancy?

Sources

[1] tommys.org

Going to sleep on your side in the third trimester (after 28 weeks) for all episodes of sleep, including night sleep and daytime naps
[2] How Pregnancy Affects Your Sleep

A rapid increase in progesterone is a primary cause of daytime fatigue and sleepiness in the first trimester. While progesterone has a sedative effect, it can also lead to less deep sleep and more nighttime awakenings.
[3] Sleep in pregnancy

Progesterone relaxes smooth muscle tissue throughout the body, which affects the muscles around the bladder and can mean more frequent trips to the bathroom during the night.
[4] Second trimester pregnancy sleep: Enjoy it while you can!

Progesterone levels remain high but the rate at which they are rising slows in the second trimester, which tends to reduce the intensity of daytime fatigue and improve overall sleep quality. Nausea has also eased for many by this stage.
[5] Week 27 - Your pregnancy journey

Towards the end of the second trimester, the growing bump begins to make finding a comfortable sleep position more difficult, and snoring can develop as nasal passages become swollen.
[6] Sleeping During the 3rd Trimester of Pregnancy

The size and weight of the growing baby and uterus cause general physical discomfort, back pain, and sore muscles in the third trimester. The ligaments around the pelvic bones also soften, which can contribute to backache.
[7] hse.ie

As the baby grows and moves lower in the pelvis, pressure on the bladder increases, making the need to urinate at night more frequent in the third trimester.
[8] Heartburn and indigestion in pregnancy sleep

Heartburn is common in the third trimester and often worse at night when lying down. Pregnancy hormones relax the valve that keeps stomach acid contained, and the growing uterus pushes on the stomach, forcing acid upwards.
[9] Restless Legs Syndrome in Pregnancy – NHS

Restless Legs Syndrome (RLS) is considered common in pregnancy and occurs most often in the third trimester. It produces an overwhelming urge to move the legs, frequently accompanied by a crawling or creeping sensation, worse during periods of rest and at night. The exact cause is not fully understood but may be linked to hormonal changes or iron deficiency.