Pregnancy Week 18: Sleep, Comfort and Your Growing Bump

8 min read

Quick answer: At 18 weeks your baby is about the size of a sweet potato, roughly 14.2cm crown to rump, with hearing well established and movements becoming more coordinated. Sleep often gets harder as your bump grows, so start practising side-sleeping now: the NHS advises sleeping on your side from around 28 weeks. A pregnancy pillow and a pillow between your knees help.

What parents need to know

Week 18 is often described as one of the most comfortable weeks of pregnancy. Your bump is showing, your energy is good, and you're likely feeling movements from your baby more frequently. But it's also a time when sleep can start to become a little more challenging as your bump grows — so let's talk about how to get the rest you need.

The Crib

Your baby at 18 weeks

Becoming more and more active each week

Roughly 14.2cm

Crown to rump

About the size of a sweet potato

Side-sleeping from: around 28 weeks

Next scan: 20-week anomaly scan

Baby's hearing: ears fully formed, hearing established

Sources: NHS, Tommy's, NCT, Pelvic Partnership. General information, not medical advice.

How big is your baby at 18 weeks?

Your baby is now about the size of a sweet potato, roughly 14.2cm from crown to rump. They're becoming more and more active each week.

What's happening with your baby?

Your baby's nervous system is maturing rapidly this week. The nerves are now being coated with myelin, a fatty protective substance that speeds up nerve signals. This means your baby's movements are becoming more purposeful and coordinated. Your baby is yawning, stretching, and may be sucking their thumb. The reproductive organs are now sufficiently developed that sex may be determinable at your 20-week anomaly scan.

Your baby's ears are now fully formed and hearing is well established. Research suggests babies can be startled by loud noises at this stage. Your baby's eyes remain sealed, but the retinas are becoming sensitive to light.

Tender close-up of a baby's feet cradled in a parent's hands, expressing love and care.

Sleep in pregnancy: what you need to know

Sleep challenges are common from the second trimester onwards. As your bump grows, finding a comfortable position becomes increasingly difficult. The NHS says that after 28 weeks the safest position to go to sleep is on your side, either left or right. Research suggests that, after 28 weeks, falling asleep on your back can double the risk of stillbirth, which may be to do with the flow of blood and oxygen to the baby. Starting to get into the habit of side-sleeping earlier in pregnancy makes this transition easier.

Sleeping on either your left or your right side is fine. From 28 weeks, go to sleep on your side at night, when you get back to sleep after waking in the night, and when you have a daytime nap. If you wake up on your back, do not worry: just turn onto your side and go back to sleep. Separately, do not lie flat on your back for long periods, particularly after 16 weeks, because the weight of your bump presses on the main blood vessel bringing blood back to your heart, and this can make you feel faint.

Tips for better sleep in pregnancy

A pregnancy pillow — a long, curved pillow that you can wrap around your body — can significantly improve comfort by supporting your bump, back, and hips simultaneously. Many pregnant women swear by them. Placing a pillow between your knees while lying on your side also helps reduce pressure on the hips and pelvis.

Other strategies that support good sleep include maintaining a regular sleep and wake time, keeping your bedroom cool and dark, avoiding screens for an hour before bed, and winding down with a relaxing routine such as a warm bath or pregnancy yoga stretches. Avoid large meals or excessive fluids close to bedtime, as heartburn and frequent urination are already common nighttime disruptions.

If you wake in the night and can't get back to sleep, try not to lie awake in bed for long periods. Getting up for a quiet, calming activity (reading, gentle stretching, warm herbal tea) and returning to bed when you feel sleepy again is often more effective than lying awake anxious about not sleeping.

Pelvic girdle pain and sleep

Pelvic girdle pain (PGP) can make sleeping particularly difficult, as turning over in bed, getting up, or being in any position for too long causes discomfort. A physiotherapy referral from your midwife can be enormously helpful. In the meantime, keeping your knees together when turning over, using a bed rail or rope to assist with getting up, and sleeping with a pillow between your knees can all reduce pain.

When to get help

Some symptoms in pregnancy can be a sign of something serious and need checking quickly. This is who to contact, and how soon.

Call 999 if:

you're bleeding from your vagina and the bleeding is heavy (soaking a period pad soon after putting it on), or you also have severe pain in your tummy, pain in your shoulder, or feel sick, faint, dizzy or lose consciousness
you have severe difficulty breathing (you're gasping, choking or not able to get words out) or your chest feels tight or heavy
you have pain and swelling in one leg and you also feel short of breath or have chest pain. A blood clot in the leg can travel to your lungs, which can be life-threatening
you have possible signs of sepsis, such as breathing very fast, being confused or having slurred speech, blue, pale or blotchy skin, a rash that does not fade when you press it, or a very high or very low temperature. Being pregnant makes sepsis more likely
you do not feel you can keep yourself safe (a mental health emergency is as serious as a physical one)

Always call 999 if you think it's a life-threatening emergency, no matter what stage of pregnancy you are.

Call your midwife, maternity unit or early pregnancy unit now if:

your baby is moving less than usual, you cannot feel your baby moving anymore, or there is a change to your baby's usual pattern of movements
you have light bleeding or spotting, even if you have no pain or only mild tummy pain
you have stomach pain that is severe or does not go away after you've rested for 30 to 60 minutes, or stomach pain with regular cramping or tightenings, lower back pain, or pain when you pee
you have a gush or trickle of fluid from your vagina, which could be your waters breaking, or vaginal discharge that's unusual for you
your skin is very itchy (for example, it keeps you awake at night), the palms of your hands or soles of your feet are itchy, or the itching is worse at night. This can be a sign of a liver condition called intrahepatic cholestasis of pregnancy (ICP) that needs urgent treatment
your breathlessness comes on suddenly, you're out of breath when you're lying down, or you're breathless and also have chest pain or feel dizzy
you have pain or swelling in one leg, usually in the calf or thigh. This could be a blood clot (deep vein thrombosis, or DVT), which is more likely when you're pregnant
you have a high temperature (38C or above), or you feel hotter than usual or shivery. A high temperature can be a sign of an infection, so it's important to get it checked

If your baby's movements change, do not wait until the next day: call immediately, even if it's the middle of the night. Do not use a home doppler to check the heartbeat yourself. Even if you hear a heartbeat, this does not mean your baby is well.

If you cannot reach them, or you're not sure what to do, call NHS 111.

Speak to your midwife or GP if:

you have not felt your baby move by 24 weeks. Most people start to feel movements between 16 and 24 weeks. If this is your first baby, you might not feel them until after 20 weeks
you're worried about your mental health, or stress, anxiety or low mood are affecting your day-to-day life. If you need urgent help for your mental health, call 111 and select the mental health option, or ask for an urgent GP appointment

Your week 18 checklist

This week:

Invest in a pregnancy pillow if sleep is becoming uncomfortable.
Practise sleeping on your side.
Manage any pelvic girdle pain with physiotherapy advice.
Prepare questions for your 20-week anomaly scan.
Continue to enjoy your baby's increasingly frequent movements.

Sources & further reading

General information, not individual medical advice. Speak to your GP, midwife or health visitor about your baby’s needs.