33 weeks pregnant: baby's development, tiredness and signs of early labour

Wow, your baby has reached the size of a pineapple! (or thereabouts).

Your baby’s development this week 

By now your baby’s nervous system is fully developed. Their bones are also starting to firm up.

Your baby’s skull is specially designed to make their exit out of the birth canal easier. It stays soft and separated until after the birth so that it can move and slide while still protecting their brain.

You may notice a diamond-shaped patch on your baby’s head near the front after they are born. This is where the skull bones have not fused together yet. There is another, smaller, soft spot towards the back of their head. These are called the fontanelles.

Find out more about your baby’s appearance after they are born.

Your pregnancy symptoms in week 33


Tiredness is likely to be kicking in now, especially if you’re having trouble sleeping. Try to put your feet up as much as you can.

Try having a milky drink before bed and let your body rest, even if you can't sleep. Avoid caffeine, which is found in coffee, tea, chocolate and some fizzy drinks. You can check your caffeine intake with our caffeine calculator.

Worrying about sleep problems can make it worse, but it's very hard not to think about them. Talk to your midwife or GP if sleeplessness becomes a real issue for you. Don’t worry, sleep problems in pregnancy won’t harm your baby. 

It might also be difficult to get comfortable in bed. This can be even more of a problem if you need to get up to wee more often because the baby is pressing on your bladder!

The safest sleeping position is on either side but not on your back. Going to sleep on your back has been found to increase the risk of stillbirth. But if you wake up on your back, don’t worry, just roll onto your side again. 

Back pain

Back pain is common in pregnancy. Many people say the pain is worse in the evening and after 28 weeks of pregnancy.

Rest is important. But lying down for long periods of time isn’t recommended when you have a bad back. It’s generally better to stay active.

Try low-impact exercises such as pilates or yoga. Swimming may help because it can take the weight off your back and bump.

What to do in week 33

Look out for signs of labour

Premature birth is when a baby is born before 37 weeks of pregnancy. About 8 babies out of every 100 in the UK are born prematurely.
If you have any of the following symptoms, phone the hospital or midwife straight away, because you could be in labour:

  • regular contractions or tightenings
  • period-type pains or pressure in your vaginal area
  • a "show" – when the plug of mucus that has sealed the cervix during pregnancy comes away and out of the vagina
  • a gush or trickle of fluid from your vagina – this could be your waters breaking
  • backache that's not usual for you.

Find out more about the signs of premature labour

Pack your hospital bag

Have you packed your hospital bag yet? It’s not too soon to get packing. There’s no harm in being prepared.

Read are our tips to help you stay stress-free in pregnancy.

Parenting after loss

Having a baby after a previous loss can cause some complicated feelings. We have information based on conversations we’ve had with parents going through this that you may find helpful.

Feeding your baby

However you choose to feed your new baby – breast, bottle or a combination of both – we have all the information you need.

1. NHS. Your newborn baby. https://www.nhs.uk/pregnancy/labour-and-birth/after-the-birth/getting-to-know-your-newborn/ (Page last reviewed: 15 March 2021 Next review due: 15 March 2024)

2. NHS. Tiredness and sleep problems. https://www.nhs.uk/pregnancy/related-conditions/common-symptoms/tiredness/ (Page last reviewed: 1 February 2021 Next review due: 1 February 2024)

3. Heazell AEP, Li M, Budd J, Thompson JMD, Stacey T, Cronin RS, Martin B, Roberts D, Mitchell EA, McCowan LME. Association between maternal sleep practices and late stillbirth – findings from a stillbirth case-control study. BJOG2017; https://doi.org/10.1111/1471-0528.14967.

4. Sue Macdonald and Gail Johnson Mayes’ Midwifery (Edinburgh: Baillir̈e Tindall Elsevier, 2017) p.531

5. Clinical Knowledge Summaries (2020) Back pain – low (without radiculopathy) https://cks.nice.org.uk/back-pain-low-without-radiculopathy#!topicsummary

6. Clinical Knowledge Summaries (2016) Antenatal care – uncomplicated pregnancy https://cks.nice.org.uk/antenatal-care-uncomplicated-pregnancy#!topicsummary

7. NICE (2015). Preterm labour and birth. National Institute for health and care excellence https://www.nice.org.uk/guidance/ng25

8. NHS Choices. Premature labour and birth. https://www.nhs.uk/conditions/pregnancy-and-baby/premature-early-labour/ (page last reviewed 04/11/2019 Next review due 04/11/2022)

Review dates
Reviewed: 11 July 2022
Next review: 11 July 2025