Week 27 of Pregnancy | How Big is Your Baby at 27 Weeks?

Pregnancy is a time of huge change for you, your body and your life. Our guide will help you through this amazing time, letting you know what to expect at each stage and, most excitingly, what your baby is up to each week.

Your baby is the size of a cauliflower!

In weight, that is! In terms of crown to heel length, we’re looking at a large leek - that’s around 34cm (13.5 inches) and your baby weighs around 1,040g (2.25 lbs).

At 27 weeks of pregnancy, your baby’s brain is becoming more active (1), with lots of neural connections forming throughout it.

Your baby’s lungs are maturing rapidly (2), ready to start breathing air after birth. The tiny sacs in their lungs - alveoli - are expanding so that there’s enough surface area for gas exchange when the time comes.

The cells of the lungs are also busy producing surfactant (3), which is needed to stop the alveoli from collapsing in on themselves.

Breathing is big business

By 27 weeks of pregnancy, your baby is spending between 10% and 20% of their time making practice breaths. They’re breathing in amniotic fluid, but these movements help to develop their lungs and the muscles they need to breathe air. 

This week, your baby is also starting to lay down fat under their skin, which will give them a rounded, paler appearance. Before 27 weeks, babies have a red, wrinkled body because there’s not much fat under their skin.

You’ll notice lots of movement around now (4), with many women feeling between three and five bouts of kicking or wriggling per hour - when the baby’s awake, that is.

You might also notice that your baby has definite waking and sleeping periods (5) throughout the day and they’re also opening and closing their eyes now.

Home or hospital?

Where to have your baby (6) is a big decision, so you should start talking to your midwife and the rest of your antenatal care team around now. Your decision will be informed by how straightforward your pregnancy is, your own personal preferences and what’s on offer in your area.

How you’re feeling at 27 weeks pregnant

At 27 weeks pregnant you’re at the end of your second trimester and you might feel some tiredness creeping back in, so rest whenever you can and try to avoid stressful situations.

You may also be experiencing more pregnancy symptoms such as constipation, backache, heartburn and piles by now, which can all combine to make life uncomfortable (you’re almost three quarters of the way through, though…).

Another delight of later pregnancy is snoring. Your pregnancy hormones can make your nasal passages swell (7), so you might notice more snoring at night and a congested feeling during the day.

If your breasts have grown dramatically, they might be making you uncomfortable too, especially at night. Wearing a supportive bra - wide shoulder straps help to carry the extra weight - is important and you might want to wear a sports-style bra in bed too.

Staying healthy at 27 weeks of pregnancy

Eating a varied diet with plenty of fibre is very important now, as this can help to relieve constipation, which in turn can prevent or relieve piles.

Gentle exercise - around 30 minutes of walking, swimming or yoga - each day will also help to lighten your mood and keep your digestive system moving along nicely. Don't forget those pelvic floor exercises (8) either! 

You might notice your stomach’s a bit squashed at this stage of pregnancy, so eat small amounts more often and don’t forget to drink lots of water throughout the day. Some women experience leg cramps in later pregnancy (9) so staying hydrated can help to prevent these.

What you need to think about at 27 weeks of pregnancy

You’re about to enter the third and final trimester of your pregnancy so you’ll be thinking more about labour and birth. It’s a good time to sign up to antenatal classes (10) - your local hospital will almost certainly run some - so you can find out more about giving birth and familiarise yourself with your maternity unit.

The next 13 or so weeks will fly by (although you might not feel like that…) so you need to have at least some of the essentials ready for your baby. Start looking at car seats, prams, cots and basic clothing so you know you’re good to go.

27 weeks is a good time to start packing your hospital bag, too. This bag will have everything you and your baby need for labour, birth and a day or so in hospital. Find out more about what you need for your hospital bag here. It's also time to think about your birth plan and start writing it.

Week 27 of your pregnancy is the last week you can fly without a letter of fitness (11) from your GP or midwife, so if you are planning a flight around now, you need to talk to your healthcare team.

Citations and References

(1) Frontiers in Human Neuroscience. ‘Fetal Functional Imaging Portrays Heterogeneous Development of Emerging Human Brain Networks.’ 2014. Web. core.ac.uk/download/pdf/78057775.pdf

(2) National Institutes of Medicine (NIH). National Library of Medicine. ‘Embryology, Pulmonary.’ 2022. Web. www.ncbi.nlm.nih.gov/books/NBK544372

(3) National Institutes of Medicine (NIH). National Library of Medicine. 'An Overview of Pulmonary Surfactant in the Neonate: Genetics, Metabolism, and the Role of Surfactant in Health and Disease.’ 2009. Web. www.ncbi.nlm.nih.gov/pmc/articles/PMC2880575

(4) Royal College of Obstetricians and Gynaecologists. ‘Your Baby's Movements in Pregnancy – Patient Information Leaflet.’ 2011. Web. www.rcog.org.uk/for-the-public/browse-all-patient-information-leaflets/your-babys-movements-in-pregnancy-patient-information-leaflet

(5) Science Daily. ‘Baby's First Dreams: Sleep Cycles Of The Fetus.’ 2009. Web. www.sciencedaily.com/releases/2009/04/090413185734.htm

(6) National Health Service (NHS). ‘Preparing for the Birth. Where to Give Birth: The Options.’ 2021. Web. www.nhs.uk/pregnancy/labour-and-birth/preparing-for-the-birth/where-to-give-birth-the-options

(7) University of Michigan Institute for Healthcare Policy and Innovation. ‘Snoring in Pregnancy - Why it Happens and How to Stop.’ 2017. Web. https://ihpi.umich.edu/news/snoring-pregnancy-why-it-happens-how-stop

(8) National Health Service (NHS). ‘Women’s Health. What Are Pelvic Floor Exercises?’ 2020. Web. www.nhs.uk/common-health-questions/womens-health/what-are-pelvic-floor-exercises

(9) National Health Service (NHS). ‘Common Symptoms in Pregnancy. Common Health Problems in Pregnancy.’ 2021. Web. www.nhs.uk/pregnancy/related-conditions/common-symptoms/common-health-problems

(10) National Health Service (NHS). ‘Preparing for the Birth. Antenatal Classes.’ 2021. Web. www.nhs.uk/pregnancy/labour-and-birth/preparing-for-the-birth/antenatal-classes

(11) National Health Service (NHS). ‘Keeping Well in Pregnancy. Travelling in Pregnancy.’ 2022. Web. www.nhs.uk/pregnancy/keeping-well/travelling