Pregnancy By Week

Pregnancy Week by Week

The Bambino Mio week-by-week pregnancy guide is your one-stop shop for all things pregnancy. The progression from tiny zygote to beautiful baby is one of the most exciting and amazing journeys we can go on and we’re here with you for every step and every craving - even the really weird ones.

One of the strangest things about pregnancy is that there are some incredible developments going on right inside your body and yet you can hardly see or feel most of them. Our 41-week guide to your pregnancy will shine a light into what’s going on. 

Did you know that by week 24 of pregnancy your baby might be able to hear you singing? Or that your baby’s heart is beating by week six?

You’ll find all of your trimesters here

Your pregnancy is divided into three trimesters, or three periods of roughly three months: 

• Your first trimester of pregnancy runs from week one to week 13
• Your second trimester is from week 14 to week 27
• Your third and final trimester runs from week 28 to week 40 (and sometimes to week 41)

We’re covering all of those weeks, one by one so that you’ll know what to expect at every stage of pregnancy and how to deal with common pregnancy symptoms like morning sickness and tiredness.

You’ll find out exactly what your baby is up to each week and our pregnancy guide also covers:

• How big your baby is each week (yes, we have a fruit and veg theme), what they’re doing and 
• How to stay healthy and look after yourself during your pregnancy
• Which midwife appointments you have and when they happen
• Your antenatal ultrasound scans at week 12 and week 20
• What you need to buy so you’re ready for your baby
• When you should join antenatal classes 
• Lots of other things you might not have thought of until you find out from us

We’ve broken down your pregnancy journey into all the baby steps (sorry) you need to sail through this amazing time like an old hand even if you’re a first timer. 

Your first trimester (week 1 to week 13)

Even though this first trimester is 13 weeks long, just like the other two, it’s your shortest one in real terms because you’re not actually pregnant at week one and week two! It’ll probably take another two weeks until you notice your missed period at week four and you take a pregnancy test.

Once you’ve had a positive pregnancy test, you’ll want to know when your baby will be due. Use the Bambino Mio estimated due date calculator to find out your probable due date so you can start planning the rest of your pregnancy.

First trimester pregnancy symptoms

You won’t look much different outwardly, but by week six or so you might be experiencing some nausea and a lot of fatigue, as well as swollen breasts. These symptoms often fade away by week 14.

Your first trimester antenatal care

You’ll start off your antenatal care programme (1) with a visit to your GP, who will refer you to your community midwife. You’ll have your first midwife appointment around eight weeks of pregnancy so we’ll tell you what you need to know about your booking-in appointment.

Your baby in the first trimester

There’s so much going on behind the scenes that it’s hard to keep up with your baby. They start off as a tiny cell that’s the size of a pinhead and by the end of your first trimester they’re almost 8cm (3in) in length and by week 13 they have all the organs and structures they need to grow into a full-sized baby.

Your second trimester (weeks 14 to 27)

By the start of the second trimester you’ll be feeling much more like your old self as those troublesome symptoms like fatigue and sickness wear off. You’ll get a bit of energy back and your appetite might have returned, so our guide has a few pointers for a healthy pregnancy diet.

It’s during your second trimester that you’ll have your 20-week scan (2). This is the ultrasound scan at which you can find out the sex of your baby if you want to. If you’ve been trying out some of our old wives’ tales to find out your baby’s sex, then you can see if they were right or not!

While your second trimester is probably the easiest one, you might still have a few niggles such as heartburn and Braxton Hicks practice contractions, so our guide can help you to deal with these annoying symptoms.

Your baby in the second trimester

By the end of your second trimester your baby will be around 34cm (13.5in) long and will weigh 1,040g (2.25lb). 

This period of intense growth includes your baby’s brain and nerve endings developing and maturing enough to feel touch and their skeleton changing from cartilage to bone!

Other milestones during your second trimester of pregnancy include the emergence of The Bump and feeling your baby’s first movements (3). You’ll have your 20-week scan around halfway through this trimester, as well as some midwife appointments, so read through our guide to find out more about them.

You’ll pass the halfway point of your pregnancy during your second trimester so we’ve got a few tips and reminders for you about finding antenatal classes, heading to the shops and also thinking about reusable nappies. 

Your third trimester (weeks 28 to 40)

The final stretch! You might go the full distance to 40 weeks of pregnancy or you might have your baby at week 37, week 39 or even week 41. Whenever your bundle of joy arrives, you’ll probably feel grateful for the end of your pregnancy because the third trimester is usually the hardest. You might have back pain, breathlessness and interrupted sleep this trimester, as well as feeling the return of the tiredness you felt in your first trimester.

As you get ever closer to delivery day, you’ll see more of your midwife and your antenatal team and you should also book yourself onto a tour of your local hospital’s labour ward so you know what to expect when the big day comes. 

Your baby in the third trimester

The third trimester is a period of rapid growth for your baby, who will put on around 2.5kg in weight and will grow from 25.4cm (10in) to 51cm (20.1in) in length between 28 weeks and 40 weeks.

Your baby’s brain also grows by a third between week 35 and week 39 and it’ll develop sulci and gyri, its characteristically human grooves and folds (4), during this period.

By 39 weeks, your baby won’t grow much more at all, as everything is pretty much “done”. Instead, your baby will start to position themselves (5) in your pelvis so they’re ready to travel through your birth canal and into your life!

How big is your baby in each week of pregnancy? 

How Big is Your Baby at One Week of Pregnancy?

How Big is Your Baby at Two Weeks?

How Big is Your Baby at Three Weeks?

How Big is Your Baby at Four Weeks?

How Big is Your Baby at Five Weeks?

How Big is Your Baby at Six Weeks?

How Big is Your Baby at Seven Weeks?

How Big is Your Baby at Eight Weeks?

How Big is Your Baby at Nine Weeks?

How Big is Your Baby at 10 Weeks?

How Big is Your Baby at 11 Weeks?

How Big is Your Baby at 12 Weeks?

How Big is Your Baby at 13 Weeks?

How Big is Your Baby at 14 Weeks?

How Big is Your Baby at 16 Weeks?

How Big is Your Baby at 20 Weeks?

How Big is Your Baby at 21 Weeks?

How Big is Your Baby at 22 Weeks?

How Big Is Your Baby at 23 weeks?

How Big is Your Baby at 24 Weeks?

How Big is Your Baby at 25 Weeks?

How Big is Your Baby at 26 Weeks?

How Big is Your Baby at 27 Weeks?

How Big is Your Baby at 28 Weeks?

How Big is Your Baby at 29 Weeks?

How Big is Your Baby at 30 Weeks?

How Big is Your Baby at 31 Weeks?

How Big is Your Baby at 32 Weeks?

How Big Is Your Baby at 33 Weeks?

How Big is Your Baby at 34 Weeks?

How Big is Your Baby at 35 Weeks?

How Big is Your Baby at 36 Weeks?

How Big is Your Baby at 37 Weeks?

How Big is Your Baby at 38 Weeks?

How Big is Your Baby at 39 Weeks?

How Big is Your Baby at 40 Weeks?

Citations and References

1. National Health Service (NHS). ‘Your Pregnancy Care. Your Antenatal Appointments.’ 2023. Web. www.nhs.uk/pregnancy/your-pregnancy-care/your-antenatal-appointments
2. National Health Service (NHS). ‘Your Pregnancy Care. 20-week Screening Scan.’ Web. www.nhs.uk/pregnancy/your-pregnancy-care/20-week-scan
3. Royal College of Obstetricians and Gynaecologists. ‘Your Baby’s Movements in Pregnancy – Patient Information Leaflet.’ 2011. Web. https://www.rcog.org.uk/for-the-public/browse-all-patient-information-leaflets/your-babys-movements-in-pregnancy-patient-information-leaflet 
4. National Institutes of Health (NIH). National Library of Medicine. ‘Brain Development (Sulci and Gyri) as Assessed by Early Postnatal MR Imaging in Preterm and Term Newborn Infants.’ 2001.  Web. https://pubmed.ncbi.nlm.nih.gov/11414646 
5. WebMD. ‘Health & Pregnancy Guide. Head Engagement in Pregnancy: What is it?’ 2023. Web. www.webmd.com/baby/head-engagement-in-pregnancy-what-is-it